Help with my left cylinder

[RDDave]

Stock RD350; The left cylinder consistently runs about 40* cooler than the right. The left cylinder's plug is a little oily and the end of the pipe is oily, too. The right is not oily. The left kills plugs, too. Both cylinders have about 90lbs compression. I've checked them several times and several different ways just to be sure. Points are .013 and timing is 1.80-1.85. Everything seems the same, but clearly something is going on with the left cylinder. The bike starts and runs good so I don't know what else to check. I know the compression is a little low, but again, the thing starts first or second kick every time. Could this be a lower ring problem on that left cylinder? Any help on this would be appreciated. Thanks!

[rodneya]

Might be worth checking your choke plunger is not leaking. The seal at the bottom hardens and can leak fuel making it run richer.

[1976RD400C]

Carb sync ok?

[RDDave]

I will definitely check that choke plunger! But wouldn't it make BOTH cylinders run rich because of the cross over? I started to take the choke plunger apart when I cleaned the carbs. But stopped when it looked tough to get the bent lock tab straightened. I was afraid I might damage the carb.

I have had both carbs apart, cleaned, verified the jet sizes and float settings. And have actually tried several different adjustments hoping to have some affect. Nothing I have tried has changed the temp difference one bit. Both needles are all the way down. And the mixture adjustments want to be out a little more than normal. But the engine does respond.

I think I have a spare left carb. Maybe I will just go through that one and stick it on to see if that does something.

Thanks for the ideas. I was out of them.

[Jspooner]

Bad coil? Swap your coils and see if the problem follows or stays.

[RDDave]

Already changed coils and went with Iridium plugs. That helped a lot with some other issues but had no effect on the temp difference.

I think the next thing I try is to clean up that spare carb, check it out, and swap it on to see if that does anything. I have even swapped the left pipe. The carb and cylinder/piston are about the only things left to swap.

The left cylinder is typically about 190* while the right is about 230*. I don't know which is more 'normal'. I have concentrated on the left because it has killed plugs and the plugs and rear tip of the exhaust pipe are a bit oily. Unlike the right.

[Striker1423]

Air screw setting? Double check that too.

[747drvr]

may have hairline cracks in intake manifold. one of my bikes had the same issue  

[RDDave]

I have changed the intakes and have adjusted and readjusted the carbs all kinds of ways. Does anyone know what the typical temp range of the cylinders should be? Although the temps are different between the cylinders, their temps are very consistent. It will be a few days before I can get back to working on the bike, but I want to swap that left carb and see if that has an effect. I appreciate all the tips and suggestions. Thanks!

[RDnuTZ]

this may be way out of left field, but have you thoroughly inspected your autolube lines from pump to inlet on carbs? All the extra oil in Left side sounds like it's getting more oil delivered than right side- maybe someone swapped a larger diameter replacement hose on that side at 1 time? Maybe something in the pump itself? Alternately or concurrently could pilot circuit air intake be blocked on that carb from bell mouth but not obvious on visual inspection?