Hot cylinder

[cipelle2@gmail.com]

My 1992 r100gs runes 200 degrees hotter on one cylinder then it dose on the other. the timing looks ok and it runs good.Dose any one have information on this?

[srankin]

This is a question that needs questions and answers to the questions before the question is answered.

How many miles on the bike? Are the valves adjusted properly? Are the carbs adjusted correctly and working correctly?
What do the spark plugs look like, is one whiter than the other?
You say it runs good, so I assume one side is not misfiring?

LOL, give us a bit more information.

To be honest, if it runs fine, don't worry about one cylinder being hotter than the other. It could just be airflow over the cylinder while the bike is sitting at idle or while it was ridden.

It is a GS, LOL, do you have more mud on one side or the other LOL? St.

[Slash2]

200 degrees is significant and I'd be looking for some kind of an air leak. Odd that you say it's running well but "well" is a rather broad description of performance from one rider to the next. Obviously I'd expect you're running correct matching plugs and as SRANKIN mentioned I'd be looking at them. A hot cylinder would usually result in a whiter plug but is the other cylinder plug fouled causing the hotter side to work harder to compensate? Condition of spark plug leads? Coil? The obvious things to check would be your air screw mixture. I'd reset them both but count the turns in so you can return them to their current setting if they are matched. What about your throttle cables? Have you done anything lately that might have caused one to hang? You can spray starter fluid around the hot cylinder to check for leaks, while the engine is running. Lots of things to consider but there's not much you can do without rolling up your sleeves.

Let us know what you find.

[schrader7032]

Welcome to the forum! Basic first question is...is this bike new to you? Or did you recently do some maintenance and now you're getting this condition? In either case, something is not right. I also agree that the difference, if measured at the same location and distance from the engine, is too much.

[snowbum]

Some good suggestions, but, let me add some things to check.
1. Remove the top of the carburetor, and remove the slide assembly. Check that the needles have very little up and down movement. Bikes of this vintage can have an aluminum alloy needle that wears badly.
see: https://bmwmotorcycletech.info/bingcv.htm
or; see https://bmwmotorcycletech.info/carb-needle-1.jpg
2. The right side carburetor has a rather nasty tendency to have problems with the intake hose sagging (the one fastening the carburetor to the HEAD. Updated parts numbering is in my bing articles. Begin with running the engine and making sure that if you spray the intake hose ends, the hose is not allowing air to get sucked-in, which will lean the mixture. If you have this problem, you may well not get the results you want by tightening the hose clamps.
3. Be sure the actual fuel levels in the bowls are correct; and spark plugs are the same heat range and tightened with a torque wrench. DO NOT overtighten...torque only to BMW torque specifications as a maximum....note that I do not agree with BMW torque settings for spark plugs (too high), and, especially not for other places the values might be listed....be cautious about those 16 foot pound settings, for example. If using anti-seize on the threads, use very sparingly, and REDUCE the settings a fair amount.

There can be a lot of things causing that much temperature variation, just as has been said, I've barely touched on a few not yet mentioned.
Snowbum

[cbclemmens]

Wait.

Before you do anything else, check the compression in both cylinders. If they are not the same, you have found the problem.

Craig