Box Stock

Carb suggestions appreciated.

D

DeeRock

New member
Hi everyone, I have this hemi predator that I purchased to replace the wimpy stock engine on a gokart that I got for my nephews to tear around out here in the country. I just happen to be on it most of the time.

So far, I have removed the governor from inside the crankcase, replaced the stock springs with 26# "white stripe" from ARC, replaced the stock cam with a Dyno DJ-1110, replaced the stock exhaust with a .990" "J" pipe, removed the factory airbox (so far only for test runs), installed a 140 E-tube and .036" jet (I also have a .037), replaced the stock flywheel with billet.

I will most likely be purchasing a different header pipe as the one I have is obnoxiously loud, but will still be much more free flowing than stock.

This engine seems to have a carb fit for a chainsaw, with the air box off, it pulls impressively strong on the low end up to mid range, but once it's past about 3.5k it's like waiting in line at the DMV.

Not really looking for for a top end monster, but an overall well performing carb.

Thanks in advance for any help/education, Derrick.
 
I don't know much about ur cam but if it's anything more wild then a bsp or a cl cam ur factory air box can't flow enough air. As for carb you have a few options you can bore it ur self ( just be gentle using a dremmel don't mess with the back just the venturi) or you can get one done for you) nr- racing has bored carbs really cheap that the jetting is already close for what it will flow. Or you can find a carb builder to do one for u.. some guys are pretty reasonable!
 
Thanks for the info.

Cam is .265 lift, looks like CL cams are around .224 - .230 so it's bigger but not really what I would consider a competition cam.

What I'm not sure of, is exactly how much carb I should be using, .615 up to .650 seems to be what is used on these engines.

I'll read up on boring it myself too, I have tons of automotive tools, I was the kid that couldn't color inside the lines though...
 
In my opinion an s/a carb works on anything from mild to wild... i would say nothing smaller then .625 but that's me
 
It's really simple to do just use some 1/4" sanding drums... don't go wild a lil bit makes a difference over stock...
 
Flywheel is a basic bolt on replacement, non adjustable but does bump the timing up 4*.

I'm more used to edelbrocks and other large engine carbs where it's a quick matter to find where you're rich and lean limits are for an engine and tune for best vacuum.

I could toss in the .037 jet and see if it runs better or worse, then retry both the .036 and .037 with the stock emulsion tube.

The engine starts quick, runs great, zero hesitation from a dead stop and doesn't miss a beat cruising around. Just runs out of pull getting out of the midrange.
 
do you have a muffler on that pipe? that would quiet it down a bunch
How are you reading rpm?
what kind of vehicle?
.036 to .037 not likely to fix your issue, unless jet is improperly sized.
The timing may have slipped, double check that first.
 
Try the stock etube in the carb along with the .037 jet and see if that doesnt help your problem first. if you have not done anything to the pilot/low speed jet then you need to make it a little bigger also, like a .024 pilot jet....you cant just leave the pilot jet stock and put a bigger main jet in these engines and expect much gain in power. Just put a muffler on the pipe you have now if it is a little too loud. I believe your problem is more likely a jetting issue than anything else
 
The holy Moses carbs are .027 with a 38 or 39 main jet. I have been told that the stock emulsion tube is best. Should have no problem with this set up. I build a motor with a 252 lift and and 670 bored carb from NR racing. Great combo
 
If you're using the stock airbox then the 36 jet is to big for it. The most I've used with stock air box was 32. Put open air filter on it and the 37 should work just fine...
 
IMO, I say get rid of the "toddler carb" all together and get a Mikuni! Go to affordablegokarts.com and get they're 22mm Mikuni. I put it on EVERY Predator 212cc I get. Easy to tune, & HUGE difference in performance! I always run either a 12.5 or a 15 pilot jet, and either a 125 or 130 main jet.
 
longhair_11e said:
If you're using the stock airbox then the 36 jet is to big for it. The most I've used with stock air box was 32. Put open air filter on it and the 37 should work just fine...
Click to expand...
33.7% difference in area between the two jets, that stock air cleaner must choke that engine off a bunch!!
 
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