I am in Mexico in the Yucatan peninsula. The closest BMW mechanic or shop I know of is in Mexico City. I am trying to get my bike running in good condition, or at least know specifically what needs to be done to it, so I can sell it. I am using a condensed version of the Hanes maintenance/repair manual. So here are my issues...
There is a slapping or deep pinging coming from the right cylinder head when the bike is idling at 1000rpms. It first started as a tapping sound so I adjusted the valve clearances. I think the noise became worse after I attempted to adjust the carburators. The ignition timing has not been adjusted for at least 7,000 miles, but I have adjusted the points twice. Also the starter seems to have a little difficulty since I adjusted the carburators. My conclusion is that it may be a main bearing failure, damaged pistons, or is associated with the carburators being maladjusted. Do you have any suggestions?

Could it be something as simple as poor quality fuel. I had the same trouble in Mexico. I was running the bike on the higher octane stuff, which was usually ok but I suspect they sometimes pass off low ocane fuel as high octane by selling it from the high octain pumps and then pocket the diffrence. there are a usually bike dealers in the bigger cities that would be able to do a compression test to see if you have any serious problems

Fuel is definitely a possible problem in Mexico, and will make the bike run very poorly.

Howqever you also say you adjusted the points twice, but haven't adjusted the timing. Ouch, that's a no-no - adjusting the points DOES change the timing and WILL cause problems. Correct drill is to adjust the points to within specs and then set the timing, either static or with a timing light. Static is easy on points systems.

Re carbs, they must be adjusted AFTER everything else is just right, and then only very very slightly. Tiny adjustments can make a big difference. 1/4 turn on one of the adjusting screws is major.

I suspect a good tune and possibly a fresh tank of gas will make a big difference.

RE: the tapping sound - if it's a light "tick-tick" it's probably valve adjustment or rocker arm end play, neither of which is fatal. If it's a deep knock, bad news. VERY unlikely to be a crank problem though, more likely worn pistons. Not super expensive to repair, and can probably go a long ways left alone.

Cranks on these are almost indestructible. 200,000 miles isn't unusual.

Get to a good mechanic! Contact the Valle de Bravo HU Community, Juan is away but will be able to point you in the right direction. Also any of the other HU Communities in Mexico will be worth contacting if they're nearby, they'll be pleased to help out.

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Grant Johnson

Seek, and ye shall find.
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One world, Two wheels.
www.HorizonsUnlimited.com