One cylinder smooth, but not the other

angus67

Welder's penetrate deeper!!
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1980 xs650, stock ignition, good plugs, ethanol free gas, fuel filter, carbs recently cleaned, new air filters in stock box, straight pipes with a baffle that looks like a can opener attacked them. Recent exhaust gaskets . The idle mix is set 2 and 1/4 on both, carbs are synced using yardstick manometer, ,
I converted the bs34s to Canadian/oceana version from kit from Mike's xs. With matching emulsion tubes. 3rd notch from top on both.
I'm trying to sell this bike to a co-worker that really wants it, and am trying to get top dollar for it. It has ran very well in the past with said setup.
The right side fires up smooth, no hiccups. The left is burpy, snappy, and erratic. At heavy throttle it backfires.
The compressions are right 150, left 130. I tried a hotter plug, it ran a little better. I tried raising the needle one notch, no difference. I switched plug wires around, problem didn't follow. Made new and on plug cap Now it's back on the 3rd notch on both were it ran good before.
Pilots 42.5, mains 140.
So is this a compression issue, or is there still junk in my pilot circuit?
 
I need to get my comp tester back from my bus to do that, or sneak one out from work.
So looks like you are leaning toward compression being the issue?
These have new stock ring a few hundred miles ago.
Perhaps cylinder is glazed? Burned valve? Xsjohns baking soda trick might come into play here
 
Possible. Not many miles on this bike when it was taken away from some boys trying to dirt bike it.
 
I just scanned thru your "removing carbon from valves to raise compression" in the tech section. I'll try that
 
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