Right / Left temp difference ... rings? valves?

[gdeangel]

L & R headers are reading 90 degree temp difference.

Bike is '88 with about 5K miles. Haven't had the bike on the road all year. It was a bear to start. Got to the carbs, and noted that the L & R carbs were way out of sync. Float levels also substantially different.

Got the carbs bench sync'd and sorted out, started bike, and there was a little smoke coming from L exhaust manifold, so I figure there's an oil leak, maybe exhaust valve issue. Get the IR thermometer, and the left header is reading 110 F, and the right is at 200 F (L is no longer smoking). Seem that could be a sign of problem with rings, but could also be something different between the L & R fuel mixtures. Air temp and pressure out the exhaust is pretty similar at the final exhaust. However, after warming it up and shutting off, noticed small thread of smoke drifting out of R exhaust - first time ever noticed it. Oil level looks ok if not high (all the way to top of window with engine off), and oil looks clean.

Advice?

[gdeangel]

Should mention temps were after idling bike for about a minute. Not worried that they are high, just that they are so different.

Thought about it overnight, and concluded that probably the L side is just running lean. I did not rejet the carbs, nor give them the full chem dip / parts washer treatment -- just carb cleaner, compressed air and nylon brush. But apparently if, in setting float height, I have the L at say, 19.5 and the R at 19, the L would be running leaner.

That's regardless of whatever might have been the reason the last owner had the carb butterflies out of sych. But I do think he had them purposely out of sync to compensate for the L & R floats that were at WAY different heights.

Other than the thread of smoke out the L exhaust, which could be from poor exhaust valve seating, not much to indicate top end / piston issue except the illusive oil leak I thought I was chasing last night. Game plan now is to change the plugs and ride it for a few days then check plug condition for tell-tale signs of running lean / rich on either side. If that doesn't yield diagnosis, or if I have more smoking issues, then I'm thinking have to check the compression, which would tell me if exhaust valve not seating and/or issue with compression rings.

Apparently not much interest in this issue, but I'll try to post back result in a few days.

[eaglerider]

Have you done a good valve adjustment???

[zekkfett]

The difference in the temps is most likely a mixture issue. The hotter cylinder is leaner than the cooler one.

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[tinlizzie37]

You have to really do a good carb cleaning, especially if the bike has been setting a long time. Disassemble the carbs, but keep them on the rack. The two plugs on the bottom front have to come out. Screw each one in and count the turns, and when assembling, put them back where they were. Keep all parts separated to each carb. Do a good soak, the pressurized carb cleaner through each orifice. Remember to put an inline filter in. Bob

[bmwpowere36m3]

Sync the carbs on the bike (manometer).