New member... am I doing it right?

[Kozi]

Just joined and this is my first build! Would love to hear your opinions on what I have done right/wrong? Or any suggestion are welcomed


Purchased this cart a year ago

Installed a fully built predator 212 along with a tav 2 30 series. 41 drive chain with 60 tooth sprocket. I managed to go 37mph on it @5K rpm .

Ran it for the first time this past weekend.. and the joy I wish I could share with you guys! So much fun.

—— issues I am looking to sort out currently.

1. If I bring the choke lever all the way down after start up I see an idle around 1600. However when I try to accelerate it just pops a bit and dies out, have to keep it running around 2000 rpm with the lever pushed up slightly.

2. Issue #1 is most likely causing issue #2. When idling at 2000 rpm the touque converter starts to engage and move the kart. Would adding some slack to the drive chain help this issue? It’s not super tight I can move it a bit with my finger.

3. Even with the 60 tooth sprocket I feel like take off from a stop is kind of weak but really picks up midrange. I am think about trying a 48 tooth but from the little I know that will reduce torque but increase top speed?


4. Is the engine maxing at 5k rpm due to the size of tires/cvt/sprocket? I shouldn’t expect to see 8K rpm right?


Thanks!

 

[anickode]

How built is fully built?

If it has stock valve springs it won't rev over 5000. If it has stock rod and flywheel, you MUST run stock valve springs.

The hesitation on take off is often the result of a lean condition.

And if you feel acceleration is lacking, a smaller sprocket will make it worse.

How about you list all the specs of your "fully built" engine? In my mind that means it's got a bigger carb, port and polished, shaved head, valve job, billet rod and flywheel, timing advance, fat cam and stiff springs.

 

[Kozi]

How built is fully built?

If it has stock valve springs it won't rev over 5000. If it has stock rod and flywheel, you MUST run stock valve springs.

The hesitation on take off is often the result of a lean condition.

And if you feel acceleration is lacking, a smaller sprocket will make it worse.

How about you list all the specs of your "fully built" engine? In my mind that means it's got a bigger carb, port and polished, shaved head, valve job, billet rod and flywheel, timing advance, fat cam and stiff springs.

Sorry lol, what fully built means to a novice has got to be different than you experienced guys.



Removed Gov
Performance carb/filter
Billet Rod
Billet flywheel
Upgraded stock lift racing cam
Upgraded valve springs
Exhaust

 

[mckutzy]

What cam exactly and lbs of springs? ...

What does the plug look like??
Did you jet accordingly to plug, or just put in new jets without plug test?

Just so we are thorough here on diagnosis... Are there any cracks in the insulator plate next to the block...
Also, how does it run on the half-cock position of the choke?...

 

[Kozi]

What cam exactly and lbs of springs? ...

What does the plug look like??
Did you jet accordingly to plug, or just put in new jets without plug test?

Just so we are thorough here on diagnosis... Are there any cracks in the insulator plate next to the block...
Also, how does it run on the half-cock position of the choke?...

Sorry I’m a newb,

Bought an upgrade kit and installed as is. Think they are 18lb springs and mod 2 cam .Have only run it for about an hour so far and have not pulled the plug. Will I be able to tell anything from looking at the plug after only an hour running?

---------- Post added at 02:15 PM ---------- Previous post was at 02:12 PM ----------

What cam exactly and lbs of springs? ...

What does the plug look like??
Did you jet accordingly to plug, or just put in new jets without plug test?

Just so we are thorough here on diagnosis... Are there any cracks in the insulator plate next to the block...
Also, how does it run on the half-cock position of the choke?...

Haven’t seen any cracks but will check.. runs great at any position of the choke. Just stumbled at the lowest setting.

 

[Kozi]

Just pulled the plug. Looks like I’m running rich?

---------- Post added at 05:35 PM ---------- Previous post was at 05:27 PM ----------

This is the carb on it.. assuming this is a jetted stock predator? anything I can adjust here?

I have a mikuni carb for another engine I’m practicing on.. should I try the Mikuni on this one?

 

[mckutzy]

Just out of curiosity... It appears the gov setup is installed in the above... Or at least a odd use of parts to have the stock setup in place???
Did you remove the gov gear inside or just bypass???

If that's the stock carb setup... What was done to add "performance carb"

What plug is that?... It doesn't look like a stock version...

 

[Kozi]

Just out of curiosity... It appears the gov setup is installed in the above... Or at least a odd use of parts to have the stock setup in place???
Did you remove the gov gear inside or just bypass???

If that's the stock carb setup... What was done to add "performance carb"

What plug is that?... It doesn't look like a stock version...

Internal governor removed, plug is autolite AR3910X.

I think it’s the stock carb jetted.

 

[mckutzy]

There's your problem... You have more air coming in and out... Needs more fuel.. Hence the need to rejet...
Some buy the jets when they buy the kit for upgrades.. I'm not sure of the numbers of the sizes...
I faintly recollect a #36, #37, #38 are the common ones... I just drilled the size needed as per a spark plug test...
You'll have to look that up, it's a bit to explain on a phone. There's also vids out there.

 

[Kozi]

There's your problem... You have more air coming in and out... Needs more fuel.. Hence the need to rejet...
Some buy the jets when they buy the kit for upgrades.. I'm not sure of the numbers of the sizes...
I faintly recollect a #36, #37, #38 are the common ones... I just drilled the size needed as per a spark plug test...
You'll have to look that up, it's a bit to explain on a phone. There's also vids out there.

Thanks! Will update once I have swapped jets.

 

[Kozi]

Assuming I will have to jet down since I’m running rich?

 

[gr8hairy1]

That's what I was thinking (please, anyone correct me if I'm wrong). Running rich "usually" means too much fuel (jet is too big) or not enough air (dirty air filter/carb issues). It's rare for the exhaust to add to that problem unless it's stock exhaust, which yours is not. Plus there would be other symptoms if the exhaust was the problem.

Normally, my first thought would make sure to thoroughly clean the carb (and inspect the butterfly valve to make sure it moves freely when you open and close the choke/throttle) before changing the jet. But it sounds like you just got everything put together. So it's not likely the carb unless you don't have a fuel filter (and there is some dirt in the gas tank), if there is a fuel filter maybe it is clogged or not working properly(defective/falling apart), or if the carb was already dirty before it was installed.

First step would be to replace the spark plug. You can clean it, but spark plugs are super cheap, and cleaning it is tedious, but cleaning it can be ok for "testing purposes" lol. #carsandcameras

To check fuel issues, disconnect the fuel line from the carb and see if gas flows freely. Inspect the fuel filter and see how it looks.
If that's good...
Take off the carb bowl (be sure to stop the gas first) and see how it looks. If it's dirty, take off the carb and take it apart to make sure it's clean. (Also, while it's apart, take the jet out and make sure it's clean with no issues). It's up to you if you want to test between each step or do all at once.
If the carb is good (and you haven't already changed the jet)...
Change the jet to a smaller size.
If that doesn't fix it...
Come back here lol.
Plus pictures. Most of us live vicariously through other people's projects and pictures make everything more interesting.

 

[65ShelbyClone]

Assuming I will have to jet down since I’m running rich?

There's nothing about your spark plug that indicates a rich mixture. Quite the opposite; the center electrode has no coloration at all which indicates a lean mixture. That black junk all around the outside doesn't matter; that's the coldest part and some carbon will always be there. At operating temperature the choke should also make it idle badly or blubber and stall, not make it run better.

That said, just looking at the plug after running all around will only provide clues that apply to how it was run soon before shut down. To complicate matters, oxygenated gasoline makes it harder to get plug readings because it leaves very little color until it's too rich.

First step would be to replace the spark plug. You can clean it, but spark plugs are super cheap,

Not so much the AR3910X plugs at $8-12 apiece. Really I think $2 NGKs are more than adequate for 99% of the engines that are getting AR3910Xs. One benefit of using a standard plug is having a ground strap that shows if ignition timing is in the ballpark. Racers go for the 3910X because it reduces the chamber volume by 0.5cc or something.

 

[Kozi]

Thanks everyone. Like I said I am a complete novice to karting, turns out I’m just an idiot. Previously built an engine with a makuni carb and never used the stock style on this predator before.

I was adjusting the choke backwards. I was starting it in the run position and running it in the start position. I think what had me confused was that if I put it in run start position it would idle at 1600 rpm but in the run position it would jump to 2200 rpm. After adjusting idle screw, it is now running great! Turning 6850 rpm and is a beast.

Thanks again and please don’t ban me for being dumb. Lol

 

[gr8hairy1]

Lol. It happens to all of us. Thanks for letting us know. It's good to keep in mind sometimes the simplest answer is the right answer (Kind of an occam's razor thing).

Plus a big thanks to 65ShelbyClone on explaining what to look at to more accurately judge lean/rich and even then, how it's not definitive, just what it was most recently running at.

Either way I learned something

 

[Kansaskart]

One of my karts is lightweight like this one, has a 212 with stage 1 and no governor, around 12" tall rears, a series 30 with a 48 tooth sprocket, I weigh 250lbs, I can throw rocks everywhere from a dead stop on gravel with a live axle and my friend clocked it on his digital Honda atv following me at somewhere between 40-43.

As far as your kart, really like the adjustable foot control spaces.

 

[Kozi]

One of my karts is lightweight like this one, has a 212 with stage 1 and no governor, around 12" tall rears, a series 30 with a 48 tooth sprocket, I weigh 250lbs, I can throw rocks everywhere from a dead stop on gravel with a live axle and my friend clocked it on his digital Honda atv following me at somewhere between 40-43.

As far as your kart, really like the adjustable foot control spaces.

Yep tried holding my phone in my hand while riding, and last time I looked down was at 42mph. Will have to find more open space soon to check top speed.

 

[65ShelbyClone]

Plus a big thanks to 65ShelbyClone on explaining what to look at to more accurately judge lean/rich and even then, how it's not definitive, just what it was most recently running at.

Either way I learned something

Glad it was informative. I consider it a good day if I learn something.

Plug readings got tougher with reformulated gas for the same reason it was phased-in: it's cleaner.

This is a plug I ran a long time ago while trying to sort the jetting with a bike. It was new to start with. For anyone that cares to play, what are its secrets?

 

[gr8hairy1]

I don't know....but I'll play lol

I'm not familiar with the white being on the ground electrode. Maybe too small of a gap? But that seems like an obvious thing to check....hmmm

I don't know. That white seems off but I can't think of what would cause it. To my uneducated eye the rest looks ok. It does seem like the top of the center electrode might be a little bit darker, but that could be a shadow. From your previous comment (if it is darker than it should be) I'd say running too rich?

 

[65ShelbyClone]

White on the ground strap is just the bright plating that became discolored from use. Darkness on the center electrode is a shadow.