Box Stock

26mm Slide

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KartRacingLA

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What size methanol jets are you guys starting out with on a pwk 26mm on methanol for a stock bore/stroke non hemi? (Flat top, .004 in the hole, .040 over rod)

Currently a .077 main, .033 pilot. Seemed to lean out last night. I could run part to half throttle and run consistant laps up to about 6800 or so rpm. If I floored it coming out of the turn it would get lazy and bog some until it picked up then would start backfiring and flames coming out the exhaust.

Thanks
 
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Skidude said:
You need a CHT gauge. You should be 335*-400*. If under temp, smaller jet. This is on the track under a load, not on the stand.
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I have an el cheapo for a temp gauge. It read a max of 226 but Im not sure I trust it. It is reading correct air temp though at the moment. I had one or two guys claim the end of the exhaust was starting to glow
 
flattop1 said:
Bog is lean .
Unless the carb is too big for the engine .
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I figured it may be a little to big and figured it may be lazy. Its a smaller, tighter turn track. This was just a test of the carb on this motor. The excessive backfire is what concerned me. It didnt do it until later in the night
 
KartRacingLA said:
What size methanol jets are you guys starting out with on a pwk 26mm on methanol for a stock bore/stroke non hemi? (Flat top, .004 in the hole, .040 over rod)

Currently a .077 main, .033 pilot. Seemed to lean out last night. I could run part to half throttle and run consistant laps up to about 6800 or so rpm. If I floored it coming out of the turn it would get lazy and bog some until it picked up then would start backfiring and flames coming out the exhaust.

Thanks
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You also need to richen up the power jet, its the one that controls the high speed mixture. The pilot is a little on the fat side for my liking, we run it at .027, the main really can vary a fair amount depending on engine setup and track, on the power jet ( its on the top near the air horn) I would start at .048 and adjust accordingly.
 
KartRacingLA said:
I thought I read somewhere that someone had stated it can cause reignition of an extremely rich condition in the exhaust
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unburned gas out exhaust pipe reignites when it gets out of the pipe and gets more air to burn the unburned gas. hear it here with HARLEYS. they put a PIPEs on it and U HAVE TO GO TO A BIGGER JET WHEN PUT ON PIPES!!! well... normally i guess, but at 3700' there is less O2 in the air so the stock jet might be fine even with PIPES on the HD? normal PSI at sea level is 14.7 PSI... at 3600 ft it is 13.0 PSI .
 
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