dag8501

Thanks. I have verified all those things. 195 psi on each cylinder, .040 squish on each side and the motor easily passes leakdown. Just wanted to make sure I wasn't missing something.

You are correct, sorry for the confusion. The left cylinder is leaner. Left carb power jet is 1 turn from completely open while the right carb power jet is closed. With this setting, the plugs look similar.

TM 38 bored to 41mm. I swapped the carbs from one side to the other and the condition was unchanged.

2026 bump. Still can't figure this one out.

Bump. No thought from the experienced troubleshooters?

As the title states, I am running into a slightly lean condition on the right cylinder according to the spark plug. My alcohol-fueled cub motor is calling for the right-cylinder power jet to be completely closed while the left-cylinder power jet is only one turn from completely open. With these power jet setting the spark plugs read identical. These are the things I have check when troubleshooting: Cleaned the carbs and swapped sides, swapped sides with the spark plug boots, leak-checked the motor (held 7 in. of vacuum overnight), and changed the spark plugs multiple times. What am I missing? Could bad reeds cause this problem?

What is the optimum swingarm angle for maximum traction on a 300 foot dirt track? I am finding conflicting information as to whether the pivot point should be lower or higher than the axle. Any help would be appreciated.

I am running into a slight lean condition at wide open throttle with my power jets wide open. I really don't want to go up on the main jet size anymore. I though about adding another power jet but changing out the current one may be a better option. Who makes the highest flowing power jet in your experience? Thanks

What would cause a difference in timing from one cylinder to another? The flywheel doesn't have any rattles or sound like it is full of sand. The motor in question is a drag ported cub on alcohol. Timing was fine at 10.5 but once raised to 11 the left cylinder looks much hotter based on a plug check. The plug was also starting to rattle out of the head. Any input would be greatly appreciated.

Any of the site sponsors offer PWK's set up for alcohol?

Finally got a chance to test the bike after removing the pump and it ran worse. The right side is still rich, but now the left cylinder plug is showing a lean condition. Got home and vacuum test the motor and it did not reveal any leaks. The carbs have large bowls, but could it be running out of fuel on that side? What other reasons would cause a lean condition on one side if the motor passes a vacuum test? Do mikuni's only run well on alcohol when using a pump? Or should I throw the mikuni's in the garbage and get me a set of PWK's? Because I am about to that point.....

I did talk to Kim at K&T and I am running the correct size needle valve, 1.8 if I remember correctly. I also did some further investigating and while my needle jet is drilled to .116, my mains are actually .102, which seems very small. I dropped that needle all the way down to the leanest position and installed a 40 pilot, but it still revs like it is too rich. And that is with the leanest needle made for my carbs. Maybe I need to drill out a new needle jet a little smaller? At wide open throttle it runs well with the power jets only 1.5 turns off of seat. Not sure why this motor does not need much fuel. My plugs are gapped at .18. I did not ohm out my stator but the coil primary was .4, the secondary was 6200 and the caps were about 5000.

Thanks for the feedback. I checked my ignition and everything seems to be within spec. It is also worth mentioning that my bike in equipped with a fuel pump and billet bowls. At K&T advice, I did change my fuel valve to a 1.8 but could the pump still be causing a rich condition? Should I set my floats a little leaner, perhaps 20mm?

I recently purchased a bike with 38mm Mikuni's bored out to 41mm. It run but not very well. Slight bog off the line and breaks up a little on the top end. Seem very rich blowing raw methanol out the pipes. Can anyone please give me some advice on the jetting/needle for these carbs for the following conditions: Sea level, 200 psi compression, plus 8 timing, 7mil, drag ported cub. I think it currently has 55 pilot and mains drilled out to .116, not sure on the needle I have trouble clearing it out at the line so the needle may be too rich. Also, I was running it with the power jets screwed in 1.5 turns from wide open. Thanks for the advice!!

I just purchases a banshee with a plus 12 swing arm but there isn't a chain guide or bracket. Are there any options out there to mount a chain guide on a round tube swing are that does not have a guide bracket. I looked all over the internet but my search was fruitless. Thanks!