thanks to this forum I was able to figure out a cure, I was told that the oil was dirty and sometimes the spring lag , which is similar to a celinoid gets stuck ,  ,I took a brass drift 1/2 in thick and 8 in long and taped it with a small hamer  in the area of the starter lag  relay, after about 5 taps bingo it engaged and started I immediately got my gear on and rode it till the oil was operating temp  , it never happened again. till sunday, I started the bike went 2mi shut it off while I gased up , it did it again ,
 since the first time it happened I have carried  the drift and hammer with me  , got them out , and taped again  it started  up , so its cold murky oil that's the problem - I rode it 45 min and no problem ,this time I changed the oil and filter  then rode it a hour let the new oil wash the cases, I don't put many miles on  so in-between the two troubles  there was maybe 900 mi , and I was allways gonna change the oil , and here after I don't start the bike unless im gonna ride it for a half hr.
BY the Way  I posted it today on craigs list today in Rochester , ny- low mi hope this helps someone  jim

Whacking starter motors with a hammer was a traditional British pastime, back in the days of yore. I well remember my Grandfather and his Clodworth 3 1/2 hp special....etc. etc.

Here's how to do it properly.

http://unlistedvideos.com/v/youtube-WrDYkksIYok.html

If the problem is that the starter motor turns without moving the engine, it is not the stater motor which is the problem. There is no solenoid on our starter motors.

The problem is in the free wheel which the motor drives. If there is some gum deposit on it, the free wheel does not bite and the motor turns for nothing.

Solution: drive the bike - after having eventually started it by pushing it - for 10 to 20 minutes at medium regime; after having replaced  minimum one third of its oil by diesel (the one you put in lorries tanks). That is often enough for degumming the free wheel. After that, of course, change the oil and the oil filter.

From then on, use exclusively some diesel oil (20w40 or 20w50) to lubricate the engine. The diesel oil is detergent and will keep your free wheel clean in the future.

thank you for your reply  im not to up on the names of these bmw parts , sometimes its hard to find someone to push you im 75  and cant run and jump on these bikes anymore,  I recent ly sold a triumph who  to a guy in your area named philippe  not you huh?   jim

No need to drain any of the oil to add diesel.  I had the same problem and fixed it by putting a whole can of Seafoam cleaner in the crankcase.  They sell it at any auto parts place.  After you put the Seafoam in, go for a ride of about 50 miles.  When you get back drain the oil while the engine is still warm and refill with Shell Rotella T6 full synthetic 10w40.  That cured my problem and the sprag was still working 12,000 miles later.

thank you , jim  not far away

Just to make it clear you should NEVER tap the starter case it can and often does crack the magnets and can cause the glue used to hold the magnets break loose it can also cause a loss of magnetism. It will not help in the case of a build up of crud in the sprag clutch because the sprag is not directly connected to the starter.

Poupy wrote:If the problem is that the starter motor turns without moving the engine, it is not the stater motor which is the problem. There is no solenoid on our starter motors.

The problem is in the free wheel which the motor drives. If there is some gum deposit on it, the free wheel does not bite and the motor turns for nothing.

Solution: drive the bike - after having eventually started it by pushing it - for 10 to 20 minutes at medium regime; after having replaced  minimum one third of its oil by diesel (the one you put in lorries tanks). That is often enough for degumming the free wheel. After that, of course, change the oil and the oil filter.

From then on, use exclusively some diesel oil (20w40 or 20w50) to lubricate the engine. The diesel oil is detergent and will keep your free wheel clean in the future.

No you should NOT use diesel fuel you use lubricating oil used in diesel engines.

Try Shell Rotella. It has roughly 3 times the detergents of regular oil.

Comes in dino and synth formulations.

I believe I said  a small hammer and used the word taped  on the engine case, I was passing along what "worked for me" to those who may encounter  this problem,  the first time it did it , I recieved all sorts a advice , ,tapping helps  but the best thing I can do is prevent it from happening , by not starting the bike and shuting it off after a  few minuets IF the bike has been sitting a long time -that's all folks

RicK G wrote:No you should NOT use diesel fuel you use lubricating oil used in diesel engines.

Why not? It is a matter of 20 minutes. Really many peoples have done it and have thus got rid of their free wheel slippage problem.

After that first attack has been achieved, the long term treatment is the use of diesel engines lubricating oil. For the rest of the bike life. Diesel oils are far from being second grade oils. Think of the pressure constraints they must endorse.  

More specific/concentrated/expensive detergents are of course possible for the job but the approach is the same: strong attack followed by long term treatment under the form of a detergent oil.

Many of the new oils are suited to both petrol and diesel engines.

Old diesel engines used a very high detergent oil because of all the sulphur in he diesel fuel but this is now eliminated so less requirement for the detergent.
But yes a high detergent oil and frequent oil changes is good.

DONT use diesel fuel in the sump though.....

With my neck on the block for the Purists,Using DIESEL FUEL to clean internals is a tried and tested
and proven safe method. For over 50 yrs i have done this and never had a problem.After a ride out with engine at temperature drain all the oil,mix 30/40%DIESEL with new oil and refill to midway on dipstick,run engine on fast idle about 1100/1200 for 10 mins allow 10 mins for oil to settle then drain change filter and refill with clean oil.The diesel/oil mix is more efficient at cleaning than the many products available.yOU WILL NOT BELIEVE THE AMOUNT OF CRUD that is in the oil/diesel mix.We all have standards, opinions based on experience so nobody is right or wrong just different.

Years ago, I was telling people to add diesel fuel in the crankcase in order to get the gunk out of the engine.
A lot of forum members did not believe me and were telling me that you cannot do that.
I am glad that few people successfully tried it.

Back in the '60's one of my first jobs was working in a gas station pumping gas and doing tune ups.  One of the things we did back then with an older car that pinged a lot was to pour a quart of diesel down the carburetor throat while fast idling.  Beside clearing out a bunch of carbon the resulting fog eliminated every mosquito for miles for at least a week.

We also put a couple quarts in the crankcase a couple days before an oil change to flush the crap out of the engine.  I don't recall any engines being hurt by either treatment.

Point-Seven-five wrote:Back in the '60's . . .

A slug of Marvel Mystery Oil in the engine, a dollop of MoS₂ in the tranny, a pint of diesel through the Solex—snack time for the Microbus.