Hoping to glean Carb perspective

123petey

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So I have some updates and curious results which have me a little stumped.

Running a vm36 single carb
25pj
200mj
P6nj
New 3.3 float needle
Floats 18mm

Quick question - I can’t find a diagram anywhere that shows 2 paper washer under the float needle. One under the needle, then the plate, then another under the plate between the carb body. I replaced the washers with new ones, too, which really changed the float height so I reset to 18mm. That’s how mine came so keeping it with 2.

Tried a 180mj and got popping and drop in throttle after holding it open so went a little richer, especially after dropping from the p8 to p6.

What’s got me stumped is initially my left cylinder ran steady and my right fired loping like a harley. Figured maybe it was the longer run on the manifold. After having idle issues I cleaned the plugs and swapped sides. Right side steady now and left wasn’t firing. Put in new plugs and right still firing steady and left intermittent. Header only gets warm and right is screaming hot so tuning the carb is impossible. Battery is 12.5v at startup so should be good. Tested coil - primary 4.2, secondary was 25. So not the coil. Can’t figure out why it was running stumbling on one side and now the other side. Doesn’t seem to be electrical
 

grizld1

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When you "swappped sides," did you move the plugs from side to side, move the wires from side to side, or both? Even with NGK's first rate quality control, you can sometimes get a bad plug fresh out of the box, and a bad plug wire is also a possibility. BTW Sudco sets up VM carbs with a richer 2.0 slide and uses leaner pilot jets to compensate. That's one way to skin the cat, but IMO not worth the extra expense.
 
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123petey

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Just swapped spark plugs. Then used new ones as well. Same results. Wires and caps stayed the same. I’m hoping the secondary coil test from cap to cap meant that the wires are ok. Am I wrong in that assumption?

I agree with you on the sudco setup which is why I stuck with the 2.5 slide
 

grizld1

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Did you mean 25 Kohm cap to cap? I'd be inclined to see if the grief follows the wires when you move them to opposite sides. Can't think why a vacuum leak would make the trouble move from left to right, but sometimes it's best just to test first and ask why later....
 

123petey

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So just wanted to follow up and give a conclusion for those that helped and/or were curious:

It was the the amount of voltage making it to the spark plugs creating a weak spark. I ran across some old info about the tci bikes stator magnet getting weak over time and some fix about welding a magnet to the magnet. I realized right around the same that I had problems I had installed the headlight and taillight. I unplugged these and the reg/rec and it started right up very strong.

Thanks to anyone who chimed in
 
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