what causes a 196cc to run fine untill full throttle

[Masonisgreat35]

i built a 196cc with ss valves
14cc head 10.8-1CR
32 degree flywheel timing
jets are 038 main 020 pilot
runs on 94 octane

gov is removed and block vented to valve cover, then to catchcan

motor idles fine and runs half throttle but full throttle it will bog down it seems and die
im assuming this is due to too large of a main jet? but from what ive read 038 main is what is common to be used with open header and air filter kits
so i was thinking maybe its starving for fuel and i need a fuel pump?
maybe i have a compression leak somehow or its magneto gap related no clue

i tried cleaning the jets, and messing with air ratio screw
i cant recall if i tried running it with choke or not
im going to order smaller jets to try
but before i did i thought id make a post n see what others think

i wasent running a pcv valve between valve cover and catchcan and just installed one but havent started the bike yet not sure if it will change anything, and i have a fuel pump that just came in mail to try if its starving for fuel, i also have a brand new coil ill throw on and see what happens incase its the coil

another thought i have as im writing this is i wonder if its valvefloat? would that cause it to seem like its bogging and cause motor to die, rpm gauge says max recorded rpm was 3090 but im not sure how accurate it is it dosent seem that accurate while idleing
i dont recall it being high rpm when it seemed to bog and die though



what are your thoughts what should i try and thanks for any info


edit, so another thing i realized is the tank is barly a quarter full, but should be enough in there to keep fuel in the lines but maybe not while riding, if thats the issue im gonna feel stupid, gonna try with half a tank full see if thats the issue, still would be great to hear any of your guys ideas though thanks

 

[BrownStainRacing]

i built a 196cc with ss valves
14cc head 10.8-1CR
32 degree flywheel timing
jets are 038 main 020 pilot
runs on 94 octane

gov is removed and block vented to valve cover, then to catchcan

motor idles fine and runs half throttle but full throttle it will bog down it seems and die
im assuming this is due to too large of a main jet? but from what ive read 038 main is what is common to be used with open header and air filter kits
so i was thinking maybe its starving for fuel and i need a fuel pump?
maybe i have a compression leak somehow or its magneto gap related no clue

i tried cleaning the jets, and messing with air ratio screw
i cant recall if i tried running it with choke or not
im going to order smaller jets to try
but before i did i thought id make a post n see what others think

i wasent running a pcv valve between valve cover and catchcan and just installed one but havent started the bike yet not sure if it will change anything, and i have a fuel pump that just came in mail to try if its starving for fuel, i also have a brand new coil ill throw on and see what happens incase its the coil

another thought i have as im writing this is i wonder if its valvefloat? would that cause it to seem like its bogging and cause motor to die, rpm gauge says max recorded rpm was 3090 but im not sure how accurate it is it dosent seem that accurate while idleing
i dont recall it being high rpm when it seemed to bog and die though



what are your thoughts what should i try and thanks for any info


edit, so another thing i realized is the tank is barly a quarter full, but should be enough in there to keep fuel in the lines but maybe not while riding, if thats the issue im gonna feel stupid, gonna try with half a tank full see if thats the issue, still would be great to hear any of your guys ideas though thanks

Pull the sparkplug and have a look see. It'll tell you what it needs.

I run a .037" main jet in my 224 with a .675" bored carb. The plug has a nice light tan color on the porcelain, runs perfect.

A 224 pulls more air then a 196, so I would say you are too rich.

Most cheaper stock sized (.580"-.590") carbs can't handle a low speed jet bigger then a .018".
What size carb do you have??
What brand is it??

Air gap or coil gap,
What flywheel??
What coil??
These will determine how much air gap you need.

ALL stock coils will pull timing out (retard) when you get in higher rpm, some start at 4000, others start at 5000, I don't know why, but they all differ for some reason.
Probably because they wasn't designed to run passed 4000 rpm since they were put on engines that was set up to be ran for utility uses.

Dover Power performance coils will not pull timing out.

Performance Coil

www.doverpoweronlinestore.com

What valve springs do you have???
Whats the installed height they are set at???

Installed height is what sets the pressure of the springs.

Say you got 26# springs. They need to be set at .850" installed height to get 26# seat pressure.

If you got them at .900" installed height, they are not 26#, they are closer to maybe.....10#.

All valve springs have a installed @ height, so they will work like they are suppose too.

I'll post examples, jus click on em and you can see where they need to be set.

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[Masonisgreat35]

Pull the sparkplug and have a look see. It'll tell you what it needs.

I run a .037" main jet in my 224 with a .675" bored carb. The plug has a nice light tan color on the porcelain, runs perfect.

A 224 pulls more air then a 196, so I would say you are too rich.

Most cheaper stock sized (.580"-.590") carbs can't handle a low speed jet bigger then a .018".
What size carb do you have??
What brand is it??

Air gap or coil gap,
What flywheel??
What coil??
These will determine how much air gap you need.

ALL stock coils will pull timing out (retard) when you get in higher rpm, some start at 4000, others start at 5000, I don't know why, but they all differ for some reason.
Probably because they wasn't designed to run passed 4000 rpm since they were put on engines that was set up to be ran for utility uses.

Dover Power performance coils will not pull timing out.

Performance Coil

www.doverpoweronlinestore.com

What valve springs do you have???
Whats the installed height they are set at???

Installed height is what sets the pressure of the springs.

Say you got 26# springs. They need to be set at .850" installed height to get 26# seat pressure.

If you got them at .900" installed height, they are not 26#, they are closer to maybe.....10#.

All valve springs have a installed @ height, so they will work like they are suppose too.

I'll post examples, jus click on em and you can see where they need to be set.

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i have a autolite 3910x plug and ive been told u cant read them like a normal plug and it will be misleading, not sure the truth behind that as im fairly new to building motors, this is the first motor ive built, should i get a stock plug and read that or will the 3910x read fine?

carb is the stock carb that come on the motor
but with a larger main jet (.038)
slightly larger pilot jet (.020)
and a 140 e tube
how would i go about measuring carb size just some calipers?

coil is stock coil same with the new replacement i have laying around
flywheel is a PVL aluminum 28degree with a 4 degree offset key for a total of 32degree the coil gap is set to .040

valvesprings are 18lb from gopowersports, after conversating with a employee i was assured i could just slap er in and not worry about any measurements, maybe he was wrong
the cam, pushrods and rockers are stock
valve lash is .003 on both sides

also not sure if its related but some extra info
.020 piston to deck
.012 piston ring gap
flattop piston (68mm) .570 compression height on billet rod
the CR was 13:1 with a .015 gasket i think?
but went instead with a .045 gasket for 10.8:1 and im running 94 octane

thanks for the help! highly appreciated

 

[BrownStainRacing]

i have a autolite 3910x plug and ive been told u cant read them like a normal plug and it will be misleading, not sure the truth behind that as im fairly new to building motors, this is the first motor ive built, should i get a stock plug and read that or will the 3910x read fine?

carb is the stock carb that come on the motor
but with a larger main jet (.038)
slightly larger pilot jet (.020)
and a 140 e tube
how would i go about measuring carb size just some calipers?

coil is stock coil same with the new replacement i have laying around
flywheel is a PVL aluminum 28degree with a 4 degree offset key for a total of 32degree the coil gap is set to .040

valvesprings are 18lb from gopowersports, after conversating with a employee i was assured i could just slap er in and not worry about any measurements, maybe he was wrong
the cam, pushrods and rockers are stock
valve lash is .003 on both sides

also not sure if its related but some extra info
.020 piston to deck
.012 piston ring gap
flattop piston (68mm) .570 compression height on billet rod
the CR was 13:1 with a .015 gasket i think?
but went instead with a .045 gasket for 10.8:1 and im running 94 octane

thanks for the help! highly appreciated

I also run the 3910x, it can't be read.

What I do is tune with a ngk bp9es plug, it's a non resistor cold plug. When you get a good reading on the ngk, then put the 3910x back in.

You got a nice build going on.
I use the 14cc head and the 3cc dished piston to keep the CR down in a 196.
I've used it on alot of builds, jus gotta watch the CR.

It's the most restricted of the stock heads, but cleaning up the casting flash and open the ports up a lil bit, and it'll make a 196, 208, and 212 come alive.

Stock carbs are not worth checking, you gotta pull em apart use a bore gauge, then measure it. They all the same 580-.590.
Jus put it back to stock jetting and save it for a stock build.

The China stock carbs are real bad for any mild performance build. The circuits are jus set to run low rpm engines, trust me I tried every thing, they are jus not good.

The Japan made carbs are much better for any kind of performance.

For your build, you need a bored SA carb.

Dover Power knows how to work a carb and are the best, imho, when it comes to SA carbs.

Have a look. They will build one for you. Give em a call, Jerry will hook you up. That .640" puts a whooping on the vm22 carbs around here.

I use this .675" and will never go back to a slide carb. I use this seller alot, around 4yrs or so now, he knows his stuff.
I wouldn't hesitate a second putting this .675" carb on your build.

Predator/Clone Kart Racing "SuperJet" Carburetor .675 SA Legal w/Jet Kit USA NEW | eBay

We include the"SuperJet" tuners Kit of 6 main jets. 035. 036. 037. Carburetor is ready for your custom engine build. Will fit all Predator Hemi and non Hemi engines and Honda GX200, BSP yellow, Greyhound, Central Machinery, and equivalent 196cc 208cc 212cc 218cc type clone engines.

www.ebay.com

 

[Masonisgreat35]

I also run the 3910x, it can't be read.

What I do is tune with a ngk bp9es plug, it's a non resistor cold plug. When you get a good reading on the ngk, then put the 3910x back in.

You got a nice build going on.
I use the 14cc head and the 3cc dished piston to keep the CR down in a 196.
I've used it on alot of builds, jus gotta watch the CR.

It's the most restricted of the stock heads, but cleaning up the casting flash and open the ports up a lil bit, and it'll make a 196, 208, and 212 come alive.

Stock carbs are not worth checking, you gotta pull em apart use a bore gauge, then measure it. They all the same 580-.590.
Jus put it back to stock jetting and save it for a stock build.

The China stock carbs are real bad for any mild performance build. The circuits are jus set to run low rpm engines, trust me I tried every thing, they are jus not good.

The Japan made carbs are much better for any kind of performance.

For your build, you need a bored SA carb.

Dover Power knows how to work a carb and are the best, imho, when it comes to SA carbs.

Have a look. They will build one for you. Give em a call, Jerry will hook you up. That .640" puts a whooping on the vm22 carbs around here.

I use this .675" and will never go back to a slide carb. I use this seller alot, around 4yrs or so now, he knows his stuff.
I wouldn't hesitate a second putting this .675" carb on your build.

Predator/Clone Kart Racing "SuperJet" Carburetor .675 SA Legal w/Jet Kit USA NEW | eBay

We include the"SuperJet" tuners Kit of 6 main jets. 035. 036. 037. Carburetor is ready for your custom engine build. Will fit all Predator Hemi and non Hemi engines and Honda GX200, BSP yellow, Greyhound, Central Machinery, and equivalent 196cc 208cc 212cc 218cc type clone engines.

www.ebay.com

thanks i originally was just replacing a valve and kept finding more and more wrong and ended up ordering a new block as mine was cracked and everything to go with it, the only things stock are the carb, side cover, camshaft, pushrods, rockers, and lifters

i was thinking of trying to learn porting probably will try in the future

i was thinking of getting a mikuni carb or something, what does SA carb stand for?
thanks for the help and the links, ill most likely order that .675 carb when i order the ngk plugs

 

[BrownStainRacing]

SA, stock appearing.
Used for outlaws, run what you brung (RWYB) racing.
The .675" is about the biggest without removing the choke.

Porting, is really nothing to it. I ruined the 1st 3 heads I did. Thinking bigger is better........well it's not true and will make your build a complete turd.

I had a guy help and teach me how the air/fuel mix travels. It doesn't take much to really get these small engines to move air fast, it's all about velocity not quantity.

The mix don't like sharp turns, getting those steep ramps into a nice slope makes a major improvement.

Opening up the intake runner slows the mix down making the engine feel lazy and gutless until it gets to higher rpm.

When you get ready for a cam, Isky racing makes cams for men.
GPS makes cams for people that like to spend money on useless crap they don't need.

For your build, the isky black mamba jr cam, 26# springs, that 675 SA carb, Dover power coil, and you will be dropping gear to calm it down.

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[Masonisgreat35]

ohh stock appearing ok that makes sence, yeah my main concern was messing up my head ill probably try on my old head first to test after i watch several videos and get an understanding on what to do and what not to, from what you say it dosent seem too difficult

yeah gps seems to be overpriced on alot of stuff, its the only site i know of besides ombwarehouse though thanks for the links thats super helpfull

ill probably order a cam, springs and carb when i can, i wanted to eventually but dident know what to go with but what you suggested sounds awesome

do you mind linking me to any and all sites for parts thats better than gps or ombwarehouse? just for future purchasing thanks for the help highly appreciated my guy

 

[BrownStainRacing]

ohh stock appearing ok that makes sence, yeah my main concern was messing up my head ill probably try on my old head first to test after i watch several videos and get an understanding on what to do and what not to, from what you say it dosent seem too difficult

yeah gps seems to be overpriced on alot of stuff, its the only site i know of besides ombwarehouse though thanks for the links thats super helpfull

ill probably order a cam, springs and carb when i can, i wanted to eventually but dident know what to go with but what you suggested sounds awesome

do you mind linking me to any and all sites for parts thats better than gps or ombwarehouse? just for future purchasing thanks for the help highly appreciated my guy

I should be out in the shop later today. I'll get pics of a stock untouched head and a head with very mild port work done.

Shop for a good dremal, flexible shafts are easier for port work. I can usally get a port done in 20-30 mins.

The most important thing I learned , is NOT to smooth out the intake runner. Keep it rough, so the mix stays busted up (atomized).

When the engine is running, the mix is pulsing back and forth between the carb and the valve (opening and closing of the valve).
A smooth intake runner will allow the mix to separate and causes very tiny puddles of fuel to fall on the bottom of the runner. Eventually the tiny puddles gets sucked in, but causes a rich condition in the combustion chamber, making it extremely hard to find the tune.

You can smooth the chamber and the exhaust runner, but NOT the intake runner.

I'll send you links for suppliers I use. I get picky on certain parts.

I get valve train parts only from dyno cams, and that's only certain parts, that I have tried, tested, measured and know that work for my builds. But, I get cams from isky. Carbs from Dover, racersproquip, or ARC.

Pistons from different suppliers, because these block are not perfect, and I'll check 3 or more pistons to get .003"-.004" piston to cylinder clearance. Same with rings for the right ring end gaps.

These small things is what makes these box roto-tiller engines work much better for karts and mini bikes.

Jus throwing fancy parts at them, usally leads to more fancy parts that are not gonna get people what they are after.
Now they got a $1000 tiller engine with fancy parts that don't make much more then stock power.

Here's mostly what I use, you already got Dover Power, and racersproquip.
Dover Power is DIY on ebay, if you see a price difference in the ebay store and Dover's site, jus call Jerry, he'll get it straight for you.

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[Masonisgreat35]

Ive tried a smaller main jet (.036) compared to the .038 i was runningand the problem got worse, instead of dieing after 3/4 throttle it now dies at 1/2 throttle with the smaller main, still running a .20 pilot jet

What is the usall turns out u guys end up at on the idle air screw? And what is the proper way to set those thanks

 

[Denny]

Sounds like you went the wrong way with jetting.

 

[Masonisgreat35]

Sounds like you went the wrong way with jetting.

I was thinking it seems as though my main jet is small if it got worse with a smaller main, biggest i got is 38 going to have to order some larger mains and try i guess, putting a new coil on currently since i got a new one and its one of the only things left on this motor from the old motor

 

[Rat]

I was thinking it seems as though my main jet is small if it got worse with a smaller main, biggest i got is 38 going to have to order some larger mains and try i guess, putting a new coil on currently since i got a new one and its one of the only things left on this motor from the old motor

I suspected lean as soon as I read your OP.

If 38 is the biggest main you have and it's lean, I'd drill out a stock one that you have no intention of ever using again. Iirc I was using a 62 main before I switched over to a Koso 24mm [Keihin] PWK copy which is jetted 38p/125m 2⅛ out on the airbleed screw

 

[panchothedog]

I don't know that I have your answer, but I have a couple of built 196 cc clone engines. Both have stock re- jetted carburators. 37 or 38 main jets, (can't remember which ) stock pilot in one and drilled to .020" in the other. They both run hard. I don't think the jet size is your problem. I don't think you are floating your valves either. It takes some pretty high rpm to do that. Plus it doesn't bog, it's more like hitting a rev limiter. Just stops pulling. You also don't need a fuel pump if you are running the stock gas tank. That will easily feed a 14 to 15 hp
engine by just gravity. Pull your fuel line to make sure it's not blocked or kinked.
Check the cap to make sure it's vented, and then fill the tank all the way up. Might be lower than you think. Sounds like you are starving for fuel.

 

[Masonisgreat35]

I don't know that I have your answer, but I have a couple of built 196 cc clone engines. Both have stock re- jetted carburators. 37 or 38 main jets, (can't remember which ) stock pilot in one and drilled to .020" in the other. They both run hard. I don't think the jet size is your problem. I don't think you are floating your valves either. It takes some pretty high rpm to do that. Plus it doesn't bog, it's more like hitting a rev limiter. Just stops pulling. You also don't need a fuel pump if you are running the stock gas tank. That will easily feed a 14 to 15 hp
engine by just gravity. Pull your fuel line to make sure it's not blocked or kinked.
Check the cap to make sure it's vented, and then fill the tank all the way up. Might be lower than you think. Sounds like you are starving for fuel.

I tried today with the tank almost full and thats when i tried with a smaller jet and it got worse, tomorrow ill try with the gas cap off and checkout the line, also have a new coil installed now i wonder if it could be the inline filter i have

edit i forgot to say i dont have the stock tank but the tank is still above the engine just higher up now so i would think gravity's alright but not sure

 

[Rat]

I tried today with the tank almost full and thats when i tried with a smaller jet and it got worse, tomorrow ill try with the gas cap off and checkout the line, also have a new coil installed now i wonder if it could be the inline filter i have

Easily could be.

A pic of what filter it is would be useful as some are more flow restrictive than others. I know some of the paper element one don't flow at all until they reach full saturation then they flow like nothing so I wonder if it could be something like that.

May be a stupid question but are you sure the flow direction is correct? I only ask because as much random expertise as I have in as broad of a range as I do... I'm still an occasional victim to my own random oversights. The last time I had on of those I put a directional motorcycle tire on backwards and had it ready to mount to the machine before I noticed... hand mounted mind you no fancy tire machines here.

 

[Masonisgreat35]

Easily could be.

A pic of what filter it is would be useful as some are more flow restrictive than others. I know some of the paper element one don't flow at all until they reach full saturation then they flow like nothing so I wonder if it could be something like that.

May be a stupid question but are you sure the flow direction is correct? I only ask because as much random expertise as I have in as broad of a range as I do... I'm still an occasional victim to my own random oversights. The last time I had on of those I put a directional motorcycle tire on backwards and had it ready to mount to the machine before I noticed... hand mounted mind you no fancy tire machines here.

I dont think its a paper filter it looks like a screen mesh if i remember, and im not 100% sure lol ill check if its flow is the correct direction

 

[Rat]

I dont think its a paper filter it looks like a screen mesh if i remember, and im not 100% sure lol ill check if its flow is the correct direction

Not completely sure since I avoid those compact ones... if I'm not mistaken I've repeatedly read those are by far one of the worst most restrictive filters.

It's hearsay because like I said won't use them myself.

 

[Masonisgreat35]

Not completely sure since I avoid those compact ones... if I'm not mistaken I've repeatedly read those are by far one of the worst most restrictive filters.

It's hearsay because like I said won't use them myself.

would u recommend using a paper element filter or is there another option, i wonder if in the petcock of the dr50 dirtbike tank im using has a filter built in and if its clogged

The lines full of gas but maybe its just clogged enough to slow flow, iduno but i remembered some other tanks ive took apart have built in filters

 

[Rat]

would u recommend using a paper element filter or is there another option, i wonder if in the petcock of the dr50 dirtbike tank im using has a filter built in and if its clogged

The lines full of gas but maybe its just clogged enough to slow flow, iduno but i remembered some other tanks ive took apart have built in filters

If the DR50 you referred to is the SSR (CRF50 clone) then yes it's extremely possible.

All fuel tanks for dirtbikes and even the Chinese motorized bicycle 2stroke kits have a peacock filter unless tampered with. I knownthe CRF style peacock actually has 2 (short one on the reserve port, tall one over the full tank tube)

Seeing as yours is busted off in the on position its worth replacing it in my mind.

I built a fuel tank from a discharged fire extinguisher and used the petcock type you mentioned on it.

 

[Masonisgreat35]

If the DR50 you referred to is the SSR (CRF50 clone) then yes it's extremely possible.

All fuel tanks for dirtbikes and even the Chinese motorized bicycle 2stroke kits have a peacock filter unless tampered with. I knownthe CRF style peacock actually has 2 (short one on the reserve port, tall one over the full tank tube)

Seeing as yours is busted off in the on position its worth replacing it in my mind.

I built a fuel tank from a discharged fire extinguisher and used the petcock type you mentioned on it.

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