Hi,

Just a question out of curiosity. I have an 87 K75 which smokes if left on the sidestand for any length of time. I know this model predates the change by BMW which pinned the rings to prevent the ring gaps from lining up and allowing oil to seep into the combustion chamber (08/88).

Is it possible to replace the rings or pistons on the early models with pistons / rings from later models to eliminate this behaviour? If so, which is it -- just rings / just pistons / both? Is it a straight forward job or is it a labor intensive job?

Thanks for satisfying my curiosity.

Rob my 93 K75 smokes if left on the side stand and it does have the pinned rings. When it does it every bug within shouting distance starts coughing and choking.
I really don't think there is a solution. I have heard that leaning them over to the right as soon as they stop will minimize it but I try to park on the center stand as often as possible.

The pinned part is the piston and said pins prevent the ring end gap being (presumably ) at the bottom of the bore which could lead to oil seeping through the gap . This is common practice on two stroke engines but in that case it's to avoid the ring end catching on a port .
I wouldn't think it worth the trouble if you have a good running bedded in engine and as Rick says his '93 model smokes anyway !
Strangely my '86 sometimes does but mostly not , or perhaps i don't always look ?

This hot topic always makes me curious. My late '86 K100 doesn't smoke, unless I start it from cold and almost immediately stop it and park it on the sidestand...because I've left my house unlocked or can't find my earplugs or any number of brain-fading reasons...then start it up again within minutes...but not always.

I recall at rallies in the '80s and '90s (when I rode Airheads exclusively) that almost every K left a vapour trail as they buzzed away just after start up, and, as Rick suggests, left mossies (and other campers) in coughing spasms. On some group rides only a few of many will smoke, and not always dependent upon the year or (mile)age of the bike.

I always try to use my centrestand. It avoids embarrassment when it does decide to have a cig. But at 26 it's old enough to smoke.

It has been so long since my bike was even on a stand that I had forgotten if it smoked. So I tried it.
All I needed was some essence of 2 stroke and it would have been like I was back at Amaroo Park watching the Mr Motorcross series back in the 70's. Go Stephen Gall.
Center stand for me from now.

rossco

remember those days well rossco ....awsome maicos and huskys and bultacos too ...then the jap invasion hit hard, had a mate that used to do club days on the road circuit, that smell of that racing fuel and oil was awesome

old gerty smokes well ....often after i plonk her on the sidestand whilst still running ...i found if i turn her off ....and wait a little while before leaning ...8 out of 10 times no smoke

Thanks for the discussion guys. Funny thing with my two bike is that the side stand for the K75 hardly causes the bike to lean at all whereas the K100 is nearly at a 60º angle. Still, the K100 never smokes and the K75 smokes at the slightest provocation. I guess I'll try some of the suggestions made here -- lean to the right after turning off to let the oil drain back to the sump, put it on the centre stand rather than the side stand, and let stand vertically after shutoff.

The short answer is leave well enough alone. No need to break into the engine to do a major pistonectomy as the prognosis is poor that the symptoms will disappear.

Cheers.

It would be cheaper to build another propstand for the right.

One reason for smoke is oil spray off the output shaft gear getting into the rearmost cylinder. Oil level has an effect on this. Don't fill above the center dot in the sight glass on level pavement.

I have 101,000 miles up.

I am using prop stand most of the time but I always kill the engine and remove gloves before dropping it onto the stand.....I get no smoke on start up. But I generally straighten it up and paddle backwards out of the garage before firing up. I am sure at 101,000 miles it could smoke a pipe but I see none.

I can only presume both of these actions mean no oil remaines in the bore on the udnerside of the piston or between the piston and the cylinder wall.

Either way its a case of dont worry, its not worth stripping the engine to stop it happening as it does not look like a defect.

92KK

K75cster wrote:It would be cheaper to build another propstand for the right.

Now that is thinking outside the square......profound my friend.

I often wonder why left hand drive countries have left hand side ...side stands??