what causes a 196cc to run fine untill full throttle

Rat

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I think it is, it was from a dirtrunner50 witch is a chinese dirtbike i think, ill probably order a new petcock for the tank if i can or just take this one apart and remove the filter if it has one
That's the one... 4 speed auto clutch manual transmission. They were (defunct afaik) definitely crf clones because everything for a crf is a direct fit from engine to body.
You'll have better luck finding a CRF50/70/90 Petcock than trying to find much of anything DR50 related

The filter is the main tube so removing it would basically give you a redundant dual reserve petcock. Not necessarily a bad thing... until you run out of fuel without warning and flipping to reserve to get it parked.
 

panchothedog

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Pull the line off, make sure that the petcock isn't plugged up ( even a little bit ) put a shorter fuel line back on without all those unnecessary bends, NO fuel filter, and
your # 38 jet and give it a try. You are buying extra parts without even getting the basics out of the way. Also, in your 1st picture, the fuel line looks kinked or pinched a little about a inch or so above the carburater inlet.
 

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Pull the line off, make sure that the petcock isn't plugged up ( even a little bit ) put a shorter fuel line back on without all those unnecessary bends, NO fuel filter, and
your # 38 jet and give it a try. You are buying extra parts without even getting the basics out of the way. Also, in your 1st picture, the fuel line looks kinked or pinched a little about a inch or so above the carburater inlet.

I saw what you're referring to Pancho, I can see it's pulled tight, but also that it's not kinked... at least not in the cameras line if sight. As for your "unnecessary parts" remark he mentioned early on in the thread that the petcock lever is busted off flush but luckily in the on position... I personally do not consire replacing that "unnecessary"

Definitely the using least amount of fuel line absolutely required to make the connection is the best way to go. Of course since automotive rubber fuel lines are not in play one must account for shrinkage and vibrations and add an extra 1/2" or just make the switch.
I find automotive 1/4" to flow better than any of the clear crap the same size or even slightly larger... dunno why, just does
 

panchothedog

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Fuel pump and brand new coil. Maybe he already had those parts on hand. The point I was trying to make is first and foremost verify that you have a good steady flow of gas. Especially with the symptoms he is describing. Running out of power ( bogging ) in the upper rpm range sounds like it's starving for fuel.
 

Rat

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Especially with the symptoms he is describing. Running out of power ( bogging ) in the upper rpm range sounds like it's starving for fuel.

You'll get no argument from me on that, mine was doing something very similar but it turned out the main was several sizes too small and I had an exhaust flow issue as well. I finally have power past 2/3 and 3/4 throttle instead of falling flat.
 
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turns out the issue was fuel supply

petcock was clogged up, i removed the two filters for main and reserve, aswell as cleaned it out pretty good, i put it back together so its switched to reserve since the handle broke flush and i cant switch it while put together

removed the inline filter on fuel line aswell as rerouted the fuel line straight from tank to carb nipple, with no twists n turns like how it was before

bike runs great tach read 8640rpm im not sure how accurate that is, when the bike was idling it was reading 800-1200 n bouncing around
i never saw it reach 8640rpm but thats what the max rpm recording was, as i passed under a streetlight i glanced n saw 7500 for sure so i know it was up there

i felt valve float im assuming around 7500-8600, not sure cudnt see what the rpm was as it was dark

the bike feels like it struggles as it climbs rpm for 1-3 seconds if u pin the throttle, then it feels like it comes alive and builds rpm quickly, i wonder if that is due to my small pilot jet any1 have any ideas on that?

thanks all for the help and suggestions sucks that it was something so simple but glad its figured out now.
 

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turns out the issue was fuel supply

petcock was clogged up, i removed the two filters for main and reserve, aswell as cleaned it out pretty good, i put it back together so its switched to reserve since the handle broke flush and i cant switch it while put together
Not a surprise, though my recommendation is still replace it on account of the busted lever... but I am petty in the respect of broken parts.
the bike feels like it struggles as it climbs rpm for 1-3 seconds if u pin the throttle, then it feels like it comes alive and builds rpm quickly, i wonder if that is due to my small pilot jet any1 have any ideas on that?
Definitely a little small on the pilot, but that's factory tuning standard practice to minimize accidents involving throttle roll. The carb is easily a size or two small as well (assuming it's the original PZ18/PZ19)
Give it a fresh plug if you haven't and take a peek at the color... I'd guess you have a lean pilot with a slightly over rich main.

Being factory tuned that way serves two main purposes
reduce low end throttle response
and reduce excess heat at peak rpm

thanks all for the help and suggestions sucks that it was something so simple but glad its figured out now.
It was definitely screaming fuel starved.
 
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Not a surprise, though my recommendation is still replace it on account of the busted lever... but I am petty in the respect of broken parts.

Definitely a little small on the pilot, but that's factory tuning standard practice to minimize accidents involving throttle roll. The carb is easily a size or two small as well (assuming it's the original PZ18/PZ19)
Give it a fresh plug if you haven't and take a peek at the color... I'd guess you have a lean pilot with a slightly over rich main.

Being factory tuned that way serves two main purposes
reduce low end throttle response
and reduce excess heat at peak rpm


It was definitely screaming fuel starved.
i like to save any money when i can on parts since shipping robs me on anything, the orings though on the petcock are cracked and dried up but seem to be holding, ill be replacing petcock in future but for now she shall do

the carb isent original but should be identical, i ordered it off ebay and it was titled 196cc stock carb replacement, i want to get a larger SA carb eventually, someone on this forum or the other gave me a link to a carb that should work well with my build, from dover performance i think? cant remember the name but i have it saved somewhere

thats interesting about the factory tuning, i dont have any plugs other than the autolite currently, will have to grab some when paid, i think theres a .020 pilot in the carb currently and i should have a .022 sitting around i can try

yeah i underestimated how picky gravity fed setups are with the way there fuel lines are ran, aswell as it was probably a bit due to the ****ty inline filter and clogged petcock, the petcock wasent clogged completly it was jus all gummd up n tht reduced the diameter of the passages

also a thought i have, i thought these stock coils limit rpm around 5-6k? is it possible my new coil i bought is a non limitied coil and allowed it to reach 8600rpm or do u figure that 8600 is false.
by the way it sounded i wudnt doubt 8600 though, and i did see 7500 on the tach breifly
 

Rat

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i like to save any money when i can on parts since shipping robs me on anything, the orings though on the petcock are cracked and dried up but seem to be holding, ill be replacing petcock in future but for now she shall do
Agreed however cracked rubber seales isn't going to hold for long so it should be a priority over goodie parts. Guess I didn't expect the shipping to be all that ridiculous to the north like it would be for Australia... blasted import dues.

the carb isent original but should be identical, i ordered it off ebay and it was titled 196cc stock carb replacement, i want to get a larger SA carb eventually, someone on this forum or the other gave me a link to a carb that should work well with my build, from dover performance i think? cant remember the name but i have it saved somewhere. thats interesting about the factory tuning, i dont have any plugs other than the autolite currently, will have to grab some when paid, i think theres a .020 pilot in the carb currently and i should have a .022 sitting around i can try
I was thinking it was a different engine, but what I said about tuning remains for an engine designed to run at a 3500rpm constant give or take 100.
Personally if Im going to use a stock type carb, Im getting a Hauyi (japanese carb) with an A/F bleed circuit adjustment
yeah i underestimated how picky gravity fed setups are with the way there fuel lines are ran, aswell as it was probably a bit due to the ****ty inline filter and clogged petcock, the petcock wasent clogged completly it was jus all gummd up n tht reduced the diameter of the passages
It doesn't take much restriction to become an issue especially at the top of the rpm range. Just remember to always use the least amount of fuel line possible to make the connection, on the straightest possible route, that won't become a snag risk and get ripped off the tank or carb.
also a thought i have, i thought these stock coils limit rpm around 5-6k? is it possible my new coil i bought is a non limitied coil and allowed it to reach 8600rpm or do u figure that 8600 is false.
by the way it sounded i wudnt doubt 8600 though, and i did see 7500 on the tach breifly
If you got it from Dover it's possible, mostly I think you preset the tach wrong whichever it may be.
Most kart motors fire spark like a 2t single... 1 spark per turn regardless of the timing cycle.

So if you did what I did without thinking (and it seems you did) you set it for 4cycle single... that unfortunately doubles the rpm read because it's expecting a regulated CDI spark every other rotation.
I had mine reading 2400 or so idle, and reving out to around 8k 🤣 just nah. Definitely not on a stock coil. At the most you might get up to MAYBE 4800 before the timing is so delayed that you've hit an immovable rpm wall even without the mechanical governor.
Some do it as early as 4k flat, other you might maybe get 5k from.

Dover is the go to at this point

 
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Agreed however cracked rubber seales isn't going to hold for long so it should be a priority over goodie parts. Guess I didn't expect the shipping to be all that ridiculous to the north like it would be for Australia... blasted import dues.


I was thinking it was a different engine, but what I said about tuning remains for an engine designed to run at a 3500rpm constant give or take 100.
Personally if Im going to use a stock type carb, Im getting a Hauyi (japanese carb) with an A/F bleed circuit adjustment

It doesn't take much restriction to become an issue especially at the top of the rpm range. Just remember to always use the least amount of fuel line possible to make the connection, on the straightest possible route, that won't become a snag risk and get ripped off the tank or carb.

If you got it from Dover it's possible, mostly I think you preset the tach wrong whichever it may be.
Most kart motors fire spark like a 2t single... 1 spark per turn regardless of the timing cycle.

So if you did what I did without thinking (and it seems you did) you set it for 4cycle single... that unfortunately doubles the rpm read because it's expecting a regulated CDI spark every other rotation.
I had mine reading 2400 or so idle, and reving out to around 8k 🤣 just nah. Definitely not on a stock coil. At the most you might get up to MAYBE 4800 before the timing is so delayed that you've hit an immovable rpm wall even without the mechanical governor.
Some do it as early as 4k flat, other you might maybe get 5k from.

Dover is the go to at this point

yeah new petcock is for sure at the top of the list on parts aswell as a dover carb and coil

the coil is not from dover, took a bit to find where i got it but found it in my amazon order history here is a link to it
Ignition Coil with Spark Plug Fit for Honda Gx110 Gx120 Gx140 Gx160 Gx200 5.5hp 6.5hp Engine Generator Lawn Mover 30500-ZE1-033 30500-ZE1-063 : Amazon.ca: Patio, Lawn & Garden

i was wondering if i had my tach setup wrong, and after looking at the instructions book it does have instructions for different engines that i dident see before somehow, aswell as a note saying warning some 4 stroke motors function like a 2stroke in terms of tach setup

but the factory setting according to instructions, on the tach is 1p1r witch is for two stroke it says, so unless i accidently switched to a different profile it should be reading correct, but with that stock coil it has to be wrong id think

ill have to go check what profile its on, i would right now but its at a buddys, if it is reading wrong that would be awesome as then it probably wasent valve float i felt and maybe i mistook it for coil limiting?

highly likely you are correct, ill report back with my findings
 

Rat

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yeah new petcock is for sure at the top of the list on parts aswell as a dover carb and coil

the coil is not from dover, took a bit to find where i got it but found it in my amazon order history here is a link to it
Ignition Coil with Spark Plug Fit for Honda Gx110 Gx120 Gx140 Gx160 Gx200 5.5hp 6.5hp Engine Generator Lawn Mover 30500-ZE1-033 30500-ZE1-063 : Amazon.ca: Patio, Lawn & Garden

i was wondering if i had my tach setup wrong, and after looking at the instructions book it does have instructions for different engines that i dident see before somehow, aswell as a note saying warning some 4 stroke motors function like a 2stroke in terms of tach setup
That is exactly the case with 98% of all lawn and race kart ignition, and many old motorcycles even, often referred to as "wasted spark ignition" and it is also that spark that is responsible for rich condition deceleration "crackle" or backfiring. Lean will backfire on deceleration but it's because of spontaneous combustion (just like predetonation) in the header from extreme heat and deceleration fuel build up specifically from dropping the throttle closed from WOT)

I digress; the 4cycle engines that wouldn't use the 2cyle single setting are going to be CDI ignition equipped engines
but the factory setting according to instructions, on the tach is 1p1r witch is for two stroke it says, so unless i accidently switched to a different profile it should be reading correct, but with that stock coil it has to be wrong id think
I made that error, the default is 2cycle single, and that's what you want it set for
ill have to go check what profile its on, i would right now but its at a buddys, if it is reading wrong that would be awesome as then it probably wasent valve float i felt and maybe i mistook it for coil limiting?
Probably, assuming the tach is reading double, that would mean 4300 rpm... so that sounds about right for the ignition to be so far retarded the engine begins to miss in most stock and generic OE replacement coils.

Once youve heard and OHV or OHC engine spin 8k or better, you dont forget what it sounds like... many of the old Honda bikes would do 10k before they were even redline
20180424_144013.jpg
highly likely you are correct, ill report back with my findings
I am 110% sure you will find you're counting double at this point
 
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That is exactly the case with 98% of all lawn and race kart ignition, and many old motorcycles even, often referred to as "wasted spark ignition" and it is also that spark that is responsible for rich condition deceleration "crackle" or backfiring. Lean will backfire on deceleration but it's because of spontaneous combustion (just like predetonation) in the header from extreme heat and deceleration fuel build up specifically from dropping the throttle closed from WOT)

I digress; the 4cycle engines that wouldn't use the 2cyle single setting are going to be CDI ignition equipped engines

I made that error, the default is 2cycle single, and that's what you want it set for

Probably, assuming the tach is reading double, that would mean 4300 rpm... so that sounds about right for the ignition to be so far retarded the engine begins to miss in most stock and generic OE replacement coils.

Once youve heard and OHV or OHC engine spin 8k or better, you dont forget what it sounds like... many of the old Honda bikes would do 10k before they were even redline
View attachment 143530

I am 110% sure you will find you're counting double at this point
So i went and took a look at my bike and the tach is set to 1p1r
witch is for 2stroke 1 cylinder or 4stroke 2cylinder it says in instructions
Im confused how its reading 8600 if its supposedly on the correct setting

is there any chance the coil i got is a non limited coil even though its listed as stock replacement?

it also says in the instructions
"Some 4stroke 1 cylinder engine is 1p1r, the setting is the same way as the 2 stroke 1 cylinder engine"
So it should be on the correct setting according to the instructions and what u told me

It says to adjust wraps around plug wire to adjust rpm if its a little low or high but i cant see that accounting for 4000rpm?

what are your thoughts, thanks

edit a thought occured, i wonder if its a poorly secured connection between tach and sparkplug wire, but i asked buddy to go and investigate and see if its loose or can slide around and he says he cudnt move it at all.
it is tightly wrapped 4 times around the sparkplug wire and secured with ziptie on the starting of the wrap and end of the wrap. so it should have a secure connection. heres a photo for visual

could it be an issue being too close to the sparkplug boot somehow?
 

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Rat

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So i went and took a look at my bike and the tach is set to 1p1r
witch is for 2stroke 1 cylinder or 4stroke 2cylinder it says in instructions
Im confused how its reading 8600 if its supposedly on the correct setting

is there any chance the coil i got is a non limited coil even though its listed as stock replacement?
Slim to none. I didn't even know unrestricted coils were a thing until I stumbled onto Dover's ebay listing by total chance
it also says in the instructions
"Some 4stroke 1 cylinder engine is 1p1r, the setting is the same way as the 2 stroke 1 cylinder engine"
So it should be on the correct setting according to the instructions and what u told me
Not entirely sure, I pulled my instructions out to refresh my memory on the setting codes. A pic of your coil itself might be helpful, I'm thinking maybe maybe yours is a different coil type than most
it is tightly wrapped 4 times around the sparkplug wire and secured with ziptie on the starting of the wrap and end of the wrap. so it should have a secure connection. heres a photo for visual
I see no Yellow wire wrapped, only the heavily insulated run that goes up the the plug connection for the display.

Besides that 4 wraps also seems like it might could be an issue, instructions say 5-10 wraps. Mine isn't even secured with a ziptie, I used a self securing wrap method and pinned the last coil with a rubber sleeve (heat shrink wrap works well too)

Adding or reducing the wrap count is what its referring to by "adjusting" not the physical position of where you placed them on the HT
could it be an issue being too close to the sparkplug boot somehow?
Not likely. I've ran them against the boot, against the coil, and everywhere between with no variation.
Idk what model of tach you have, but there is a chance the program code in it is bad or glitched and it's mistranslating the signal

I use a Runleader RL-HM035L, which is 12v not CR2032 watch battery powered
 

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Slim to none. I didn't even know unrestricted coils were a thing until I stumbled onto Dover's ebay listing by total chance

Not entirely sure, I pulled my instructions out to refresh my memory on the setting codes. A pic of your coil itself might be helpful, I'm thinking maybe maybe yours is a different coil type than most

I see no Yellow wire wrapped, only the heavily insulated run that goes up the the plug connection for the display.

Besides that 4 wraps also seems like it might could be an issue, instructions say 5-10 wraps. Mine isn't even secured with a ziptie, I used a self securing wrap method and pinned the last coil with a rubber sleeve (heat shrink wrap works well too)

Adding or reducing the wrap count is what its referring to by "adjusting" not the physical position of where you placed them on the HT

Not likely. I've ran them against the boot, against the coil, and everywhere between with no variation.
Idk what model of tach you have, but there is a chance the program code in it is bad or glitched and it's mistranslating the signal

I use a Runleader RL-HM035L, which is 12v not CR2032 watch battery powered
i dont have a pic of the coil, but it is identical looking to a stock coil and i didn't see a difference, ill include a pic off the amazon listing i bought it from

my tach has no yellow wire and only the one black wire, it does say wrap red wire around sparkplug wire in instructions when the wire isent red, maybe the wire is red within the black sheath and its just a heat shield thing and i have to cut back the black sheath and wrap the wire thats in it around, instead of wrapped around with the black sheath, but the instructions book mentioned no such thing

my tach instructions say 4-5 wraps instead of ur books 5-10, do you figure thats correct or my instructions are poorly translated or something when created

i was thinking of heat shrinking it on but didn't want to incase i needed to adjust wraps, aswell as i didn't wana pop boot off the plug wire to put the shrink wrap on

im aware its talking about the wire wrap count when it says adjusting, the way i worded my post may of not made it seem so, and im not sure what HT stands for sorry if its obvious

i figured it would make no difference in where the tach wire was wrapped, but thought id ask
i wonder if its just my tach, i cant find a brand name in the instructions and my buddy says there isent a name on the tach, i dont remember a name being on the tach either, it does use one of those small circle batterys

if i were to replace the tach with another what brand would u recommend and is the runleader RL-HM035L decent

thanks for the help this is quite the intriguing mystery
 

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Rat

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i dont have a pic of the coil, but it is identical looking to a stock coil and i didn't see a difference, ill include a pic off the amazon listing i bought it from
Standard issue Honda/Clone generic coil definitely rpm restricted between 4k and 4500
my tach has no yellow wire and only the one black wire, it does say wrap red wire around sparkplug wire in instructions when the wire isent red, maybe the wire is red within the black sheath and its just a heat shield thing and i have to cut back the black sheath and wrap the wire thats in it around, instead of wrapped around with the black sheath, but the instructions book mentioned no such thing
This is extremely odd because excessive cladding will weaken the signal and therefore read wrong no matter what... I think maybe you got a POS tach, but only pics of the signal line off the HT and layed out would tell for sure.

Typically theres 2-4 inches of of shielding below the connector (only there to protect the connector and its connection to the induction lead) and 10-14 inches of steel stranded 24AWG wire which is the induction wire... I've only ever seen those in yellow cladding even on the CR2032 powered units
my tach instructions say 4-5 wraps instead of ur books 5-10, do you figure thats correct or my instructions are poorly translated or something when created
Honestly no clue I used one like yours and it quit working before 1hr was clocked. I've always gone 10 loops and left it alone... if it reads 100rpm off it's not enough to matter. Besides you can only hear 100rpm difference below 3k when tuning the carb settings anyhow
i was thinking of heat shrinking it on but didn't want to incase i needed to adjust wraps, aswell as i didn't wana pop boot off the plug wire to put the shrink wrap on
its better to unscrew the HT from the coil (sometimes they're held with an unnecessary dab of glue) slide a larg wrap up, squirt some dielectric grease into the HT port, trim maybe 1/4" of the HT and crank it back in, then set you induction loops and give a bit of heat.

The dielectric grease will keep moisture and corrosion out better than the little boot that slides down alone... in fact it does well enough you almost don't even need the boot (use it if you have it, doesn't matter if you don't)
im aware its talking about the wire wrap count when it says adjusting, the way i worded my post may of not made it seem so, and im not sure what HT stands for sorry if its obvious
High Tension aka the spark plug wire itself. Overhead powerlines are often referred to as High Tension wires as well...in short it just means it something you seriously want to avoid being zapped by
i figured it would make no difference in where the tach wire was wrapped, but thought id ask
i wonder if its just my tach, i cant find a brand name in the instructions and my buddy says there isent a name on the tach, i dont remember a name being on the tach either, it does use one of those small circle batterys
Seems like a cheap knockoff of one of Runleaders other models meant more for machines that dont have a 12v supply (competition karts and the like)
if i were to replace the tach with another what brand would u recommend and is the runleader RL-HM035L decent
Runleader is a good brand so I would recommend them every time. As for the RL-HM035L model... only if you plan running some type of 12v electrical sytem with the capacity to charge the battery and lights or already do. That specific model tach isn't worth the battery to run it or the hassle to recharge periodically otherwise.
side note, the RL-HM035LE (if you can even find one) features a thermocouple to be pinned down by the spark plug (ring connector) to give you a temp monitor... it's also 12v powered
thanks for the help this is quite the intriguing mystery
It's fuggin annoying because there no way your engine is idling as high as that thing probably says or spinning more than 4800 an its safe to believe it's only got a max potential of 4300.

A kart will creep (or try to) at around 2800-3200, having a Hillard centrifugal or a Comet clone either one is an irrelevant factor in that matter.

Stock valves are almost always 10.5 or 10.8, they tend to float around the same point the coil becomes out of sync with the mechanical timing (4k-4800 crap shoot)
It takes 18# valve springs minimum just to make 5k. Im running 22# with split keepers and a Mod2 Dover cam so 5k is a cake walk with everything tuned and playing nice together

The bottom line is on an ungoverned but otherwise full stock engine if you can crank anything over 4200 count yourself the lucky owner of an oddball.

Without the unrestricted coil from Dover but all the other work I've done prior to that I could bounce between 4300-4500 but hit a definitive rpm wall that just could not be crossed
 
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Standard issue Honda/Clone generic coil definitely rpm restricted between 4k and 4500

This is extremely odd because excessive cladding will weaken the signal and therefore read wrong no matter what... I think maybe you got a POS tach, but only pics of the signal line off the HT and layed out would tell for sure.

Typically theres 2-4 inches of of shielding below the connector (only there to protect the connector and its connection to the induction lead) and 10-14 inches of steel stranded 24AWG wire which is the induction wire... I've only ever seen those in yellow cladding even on the CR2032 powered units

Honestly no clue I used one like yours and it quit working before 1hr was clocked. I've always gone 10 loops and left it alone... if it reads 100rpm off it's not enough to matter. Besides you can only hear 100rpm difference below 3k when tuning the carb settings anyhow

its better to unscrew the HT from the coil (sometimes they're held with an unnecessary dab of glue) slide a larg wrap up, squirt some dielectric grease into the HT port, trim maybe 1/4" of the HT and crank it back in, then set you induction loops and give a bit of heat.

The dielectric grease will keep moisture and corrosion out better than the little boot that slides down alone... in fact it does well enough you almost don't even need the boot (use it if you have it, doesn't matter if you don't)

High Tension aka the spark plug wire itself. Overhead powerlines are often referred to as High Tension wires as well...in short it just means it something you seriously want to avoid being zapped by

Seems like a cheap knockoff of one of Runleaders other models meant more for machines that dont have a 12v supply (competition karts and the like)

Runleader is a good brand so I would recommend them every time. As for the RL-HM035L model... only if you plan running some type of 12v electrical sytem with the capacity to charge the battery and lights or already do. That specific model tach isn't worth the battery to run it or the hassle to recharge periodically otherwise.
side note, the RL-HM035LE (if you can even find one) features a thermocouple to be pinned down by the spark plug (ring connector) to give you a temp monitor... it's also 12v powered

It's fuggin annoying because there no way your engine is idling as high as that thing probably says or spinning more than 4800 an its safe to believe it's only got a max potential of 4300.

A kart will creep (or try to) at around 2800-3200, having a Hillard centrifugal or a Comet clone either one is an irrelevant factor in that matter.

Stock valves are almost always 10.5 or 10.8, they tend to float around the same point the coil becomes out of sync with the mechanical timing (4k-4800 crap shoot)
It takes 18# valve springs minimum just to make 5k. Im running 22# with split keepers and a Mod2 Dover cam so 5k is a cake walk with everything tuned and playing nice together

The bottom line is on an ungoverned but otherwise full stock engine if you can crank anything over 4200 count yourself the lucky owner of an oddball.

Without the unrestricted coil from Dover but all the other work I've done prior to that I could bounce between 4300-4500 but hit a definitive rpm wall that just could not be crossed
agreed it is very annoying lol, im going to go mess with the bike n see what it reads on other settings before i order a new tach, i like the idea of the temp gauge tachs have you used them before and do they work well/accurate? i read its more accurate to mount the temp sensor to the head than sparkplug whats your thoughts

i found a runleader with temp read and circle battery
the RL-HM035A
Runleader Digital Tach Hour Meter,Engine Temperature Gauge,Alert RPM & Temp,Backlights Display for Lawn Tractor Compressor Generator Snowmobile Marine Jet Ski Pit Bike (RL-HM035A-M5) : Amazon.ca: Automotive
i think ill order this if i cant get the other one to work aswell as a dover coil to try after i get rpm reading right

the motor is stock cam/lifters/pushrods/rockers
new block with headstuds, a 14cc head with SS valves and 18lb springs
new stock crank
10.8:1 compression on 94octane
billet stock length rod/flattop piston .020 piston to deck .012 ring gap
PVL flywheel 28degree with 4 degree offset key total of 32degrees
coil set at .040
.003 valvelash exhaust and intake
gearing 10t clutch to 20t to 10t to 50t rear sprocket
some info about the motor if interested

thanks for the info and help
 

Rat

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agreed it is very annoying lol, im going to go mess with the bike n see what it reads on other settings before i order a new tach, i like the idea of the temp gauge tachs have you used them before and do they work well/accurate? i read its more accurate to mount the temp sensor to the head than sparkplug whats your thoughts
Honestly running a temp sensor is pointless unless your running a 2cycle which will run like a diesel until it locks up or melts the piston once you get a temp reading of 415°F off the plug base. Litteraly no ignition needed, and at that temp tossing the choke has the opposite effect, it runs faster instead of flooding.
Unless you want to perform surgery and risk ruining the entire unit to replace the exsisting thermocouple with a threaded one and them figure out where to drill in to the block and match the treads without causing a leak or worse... there is no better placement for accuracy than a ring under the spark plug
i found a runleader with temp read and circle battery
the RL-HM035A
Runleader Digital Tach Hour Meter,Engine Temperature Gauge,Alert RPM & Temp,Backlights Display for Lawn Tractor Compressor Generator Snowmobile Marine Jet Ski Pit Bike (RL-HM035A-M5) : Amazon.ca: Automotive
i think ill order this if i cant get the other one to work aswell as a dover coil to try after i get rpm reading right
I have used the RL-HM035LT (12v blue LED) version of that exact tach and they seem very accurate.
As for temp sensor placement, spark plug base is most ideal and the most simple to mount; the spark plug does act as a crude heat sink for the bore afterall.
the motor is stock cam/lifters/pushrods/rockers
new block with headstuds, a 14cc head with SS valves and 18lb springs
new stock crank
10.8:1 compression on 94octane
billet stock length rod/flattop piston .020 piston to deck .012 ring gap
PVL flywheel 28degree with 4 degree offset key total of 32degrees
coil set at .040
.003 valvelash exhaust and intake
gearing 10t clutch to 20t to 10t to 50t rear sprocket
some info about the motor if interested

thanks for the info and help
If you're going to get a dover ignition, you may as well grab a Mod2 cam and 22# springs while you're at it... waste of a coil otherwise.

I'm running a 208cc
Hardened SS lifters and rods
Stock valves
Stock 16cc head
22# springs with split retainers and hardened stainless lash caps
HD Champion 1.1:1 rockers (old style)
Mod2 Dover Cam
+0.40 conrod and flattop piston (flush to deck)
stock flywheel 5.5° offset (+/-0.5 because 1/4" key)
Dover Coil airgap at 0.010
0.0 I/E lash (just enough wiggle to know the valves are fully closed, set cold)
9t on the clutch 56t on the rear

I was playing around and spun out a couple 5k pulls feeling froggy... Tav 2 quickly pulled the rpm under 4800 but ground speed was unaffected by that
 
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Honestly running a temp sensor is pointless unless your running a 2cycle which will run like a diesel until it locks up or melts the piston once you get a temp reading of 415°F off the plug base. Litteraly no ignition needed, and at that temp tossing the choke has the opposite effect, it runs faster instead of flooding.
Unless you want to perform surgery and risk ruining the entire unit to replace the exsisting thermocouple with a threaded one and them figure out where to drill in to the block and match the treads without causing a leak or worse... there is no better placement for accuracy than a ring under the spark plug

I have used the RL-HM035LT (12v blue LED) version of that exact tach and they seem very accurate.
As for temp sensor placement, spark plug base is most ideal and the most simple to mount; the spark plug does act as a crude heat sink for the bore afterall.

If you're going to get a dover ignition, you may as well grab a Mod2 cam and 22# springs while you're at it... waste of a coil otherwise.

I'm running a 208cc
Hardened SS lifters and rods
Stock valves
Stock 16cc head
22# springs with split retainers and hardened stainless lash caps
HD Champion 1.1:1 rockers (old style)
Mod2 Dover Cam
+0.40 conrod and flattop piston (flush to deck)
stock flywheel 5.5° offset (+/-0.5 because 1/4" key)
Dover Coil airgap at 0.010
0.0 I/E lash (just enough wiggle to know the valves are fully closed, set cold)
9t on the clutch 56t on the rear

I was playing around and spun out a couple 5k pulls feeling froggy... Tav 2 quickly pulled the rpm under 4800 but ground speed was unaffected by that
i tried different settings on tach witch caused it to read double the rpm and read up to 12k witch clearly is wrong,
so it is on the right setting (1p1r) its just reading low at idle and reading high when riding.
i think its something to do with the way the tach is attached to the plug wire and im going to try 10 wraps to see if its more accurate before i order another tach to try

the tach was reading 2080rpm when the bike was trying to creep forwards, and my clutch most likely has overheated stretched springs so id assume that wud make the rpm it engages at slightly lower

another thing that i noticed is a poping sound at idle, aswell as a bit after letting off throttle after a pull too

the popping on decel after a pull i assume is just unburnt fuel in the exhaust would i be correct about that?

the popping at idle is what concerns me as im not sure if it is normal or not
its not loud but u can hear it if u listen, it sounds soft
maybe its lean
maybe its just due to the short open pipe
maybe its just unburnt fuel
maybe its something to do with valve lash
honnestly no clue im not sure, what is your thoughts on that

howcome some people set lash at 0, i thought when metal heats up it expands and that would be an issue if its set at 0

the bike also will lurch forward repeatedly every 3 seconds or so while holding the throttle open riding, mostly at half throttle or more it will happen, i didn't notice it happening at low throttle

also i read 3 turns out is usually about where the idle air screw shud be
but is that half or full turns
full turn in my mind being the flathead rotates 180degrees twice

it sounds like the bike is idleing a little high and when i went to mess with idle screw and idle air screw the popping got worse as i turned the idle air out, i think, i cant remember now, damn marijuana cigrits lol

what is the proper way to set the idle air to begin with, i assume let the bike warm up then make changes? but to start with to let it warm up what would i set it at 3 turns out?

im gonna order some plugs for testing eventually to see if the bike is rich or lean as the autolite plug i have cannot be read correctly
thanks for any info, highly appreciate it
 
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Rat

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i tried different settings on tach witch caused it to read double the rpm and read up to 12k witch clearly is wrong,
so it is on the right setting (1p1r) its just reading low at idle and reading high when riding.
i think its something to do with the way the tach is attached to the plug wire and im going to try 10 wraps to see if its more accurate before i order another tach to try

the tach was reading 2080rpm when the bike was trying to creep forwards, and my clutch most likely has overheated stretched springs so id assume that wud make the rpm it engages at slightly lower
That's not a bad idle speed, my 208 can idles as low as 1990 but only already heated up and it stumbles, it definitely prefers closer to 2050
another thing that i noticed is a poping sound at idle, aswell as a bit after letting off throttle after a pull too

the popping on decel after a pull i assume is just unburnt fuel in the exhaust would i be correct about that?
Correct decel crackle is unspent fuel igniting on the superheated header walls... it is far worse if the engine is running too lean. If the engine is running lean enough you can actually get detonation in the header as much as 20 seconds after the engine stops rotating entirely.
howcome some people set lash at 0, i thought when metal heats up it expands and that would be an issue if its set at 0
It's not an issue because the difference in thermal expansion between steel and aluminum add a few thousandths lash. So if you set the lash to Zero cold, by the time you get to peak temp your lash will have opened up... they can be harder to start, but they do fine once warm enough to hold an idle, and really rip once they hit peak temp
the bike also will lurch forward repeatedly every 3 seconds or so while holding the throttle open riding, mostly at half throttle or more it will happen, i didn't notice it happening at low throttle
Sounds like clutch slip or something hung up that frees briefly (warped clutch shell? Idk)
also i read 3 turns out is usually about where the idle air screw shud be
but is that half or full turns
full turn in my mind being the flathead rotates 180degrees twice
The AF setting varries slightly by carb type, and carb size.
MOST default at 2 turns out, with the tuning guideline being:
3 or more, drop the pilot size one and retest
less than 1.5 raise the pilot one size and retest

Testing meand counting how many turns out to achieve the maximum idle speed before it starts falling off, when you've identified the position (ideally between 1¾ and 2¾ turns) you turn it back in ¼ turn and call it good on the assumption it's relatively close to the default of 2

Full turns is 360° meaning your AF is no less than 1 turn rich (in cuts off the idle air inlet, out opens to let more ait into the idle circuit)
what is the proper way to set the idle air to begin with, i assume let the bike warm up then make changes? but to start with to let it warm up what would i set it at 3 turns out?
run it around for a few minutes to get it hot then put your machine on stands or cinderblocks to get the rear wheels off the ground.

Set your idle screw to hold 3k, then adjust the A/F all the way in to soft seat, back it out 2 and let the engine have 30-60 seconds to level off with the change.

start adding ¼ turns out listening to the engine and watching the tach giving it tue 30-60 to level off... when the numbers start to drop STOP

turn it back in that last quarter turn and let it level off.

Once leveled out turn it in ¼ if the rpm is unphased your AF is set (hopefully between 1¾ and 2¾) and now you can adjust your idle scew out to actually idle setting it as low as possible without stumbling badly or more importantly stalling outright.
im gonna order some plugs for testing eventually to see if the bike is rich or lean as the autolite plug i have cannot be read correctly
thanks for any info, highly appreciate it
NGK!!
I'm in the mountains running BP8ES [2912] but I also have a fairly hot running far from stock build done from a winter use only designated engine... your ideal plug is more likely to be closer to BP6ES [7811]
 
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That's not a bad idle speed, my 208 can idles as low as 1990 but only already heated up and it stumbles, it definitely prefers closer to 2050

Correct decel crackle is unspent fuel igniting on the superheated header walls... it is far worse if the engine is running too lean. If the engine is running lean enough you can actually get detonation in the header as much as 20 seconds after the engine stops rotating entirely.

It's not an issue because the difference in thermal expansion between steel and aluminum add a few thousandths lash. So if you set the lash to Zero cold, by the time you get to peak temp your lash will have opened up... they can be harder to start, but they do fine once warm enough to hold an idle, and really rip once they hit peak temp

Sounds like clutch slip or something hung up that frees briefly (warped clutch shell? Idk)

The AF setting varries slightly by carb type, and carb size.
MOST default at 2 turns out, with the tuning guideline being:
3 or more, drop the pilot size one and retest
less than 1.5 raise the pilot one size and retest

Testing meand counting how many turns out to achieve the maximum idle speed before it starts falling off, when you've identified the position (ideally between 1¾ and 2¾ turns) you turn it back in ¼ turn and call it good on the assumption it's relatively close to the default of 2

Full turns is 360° meaning your AF is no less than 1 turn rich (in cuts off the idle air inlet, out opens to let more ait into the idle circuit)

run it around for a few minutes to get it hot then put your machine on stands or cinderblocks to get the rear wheels off the ground.

Set your idle screw to hold 3k, then adjust the A/F all the way in to soft seat, back it out 2 and let the engine have 30-60 seconds to level off with the change.

start adding ¼ turns out listening to the engine and watching the tach giving it tue 30-60 to level off... when the numbers start to drop STOP

turn it back in that last quarter turn and let it level off.

Once leveled out turn it in ¼ if the rpm is unphased your AF is set (hopefully between 1¾ and 2¾) and now you can adjust your idle scew out to actually idle setting it as low as possible without stumbling badly or more importantly stalling outright.

NGK!!
I'm in the mountains running BP8ES [2912] but I also have a fairly hot running far from stock build done from a winter use only designated engine... your ideal plug is more likely to be closer to BP6ES [7811]
NGK is probably the route ill go on plugs, it gets to 40c to 45c here in the summer with -10c to -20c in winter if that matters

would colder weather affect the idle air screw setting due to air density change or something? or am i thinking too hard about it

i noticed u dident comment on the popping at idle, would u say its concerning or should i not worry about it

ill try messing with tach connection to plugwire aswell as idle air screw to improve idle im sure i have it set a bit off after reading how u described to set it up
 
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