Forum bmwbike.com

Thank-you to everybody who answered my question about the regulator. I bought an electronic one and now its working fine. I have a new problem..After driving around for a while I notice my top speed in each gear starts to drop and I get smoke puffing out of the breather tube off the bottom of the oil pan. The timming seems to be fine and the oil level seems ok too? Thanks.

Hallo,
it seems you got a heat problem, I think your piston was getting too hot so he is starting to jam (in german "Kolbenklemmer"). Do you have (had) a new piston? what is your jet-size, I drive with a 115.
greetings
rolf

It sounds like the piston is beginning to seize from friction and heat. Perhaps some damage has been done already, allowing combustion to blow past the rings and pressurize the crankcase and come out of the breather.

You might take the cylinder apart and check the situation. It may be scored or galled, and need a boring to next oversize and a new piston.

Thank you for the info Allan. I will look at the piston and check for wear and check the rings. Trevor