points closing up after 100 miles?

[Rohls]

Hi All,

Something that has been bothering me for a while now...

'75 R90/6 with 75K on her.

I have replaced the points twice in the last year.

Currently the bike runs great, but I'll go about 100 miles and the bike will sputter and die for no real reason. I go straight to the points and see that they are closed up (no gap) (!). I fix it and carry on....

This has happened many times.

Seems like the points plate is just sliding/slipping up for no real reason...

The screw that holds the plate has the 'wave washer'...maybe that's the culprit?

What part is worn out that it's causing this?

Much appreciated!

What should I do?

[Bamboo812]

Have you been lubricating the felt block? Maybe tighten the screw a 'bit' more?

[Rohls]

Thanks Bamboo812.

The felt is lubed and the screw is tight as of 6:45am this morning after yesterday's ride...:/

Any other ides to keep that screw tight? I don't want to crank on it too much..

[Duane Ausherman]

Is the screw on the points loose when you open it up? If it is still tight, then that isn't the problem.

If the points plate moves, the points won't close up, only the timing will change. The gap won't change.

Maybe a reread of my article on points will help understand how it works. http://www.w6rec.com/duane/bmw/points/index.htm

[George Ryals]

Wasn't there a thread a while ago about some "Chinese points" that had rubbing blocks that wore rapidly due to out of spec material?????? Next time you are in there measure the height of the block to have a reference point for the next time the gap closes up.

[Kurt in S.A.]

Hmmm...I thought that the problem with the Chinese points was that the rubbing block was so tall, it was impossible to even time the bike. If that was the case, the bike couldn't be started to wear down the rubbing block.

Kurt in S.A.

[bbelk]

I had an old Datson that would lose its point gap in a couple hundred miles. I attributed it to a pitted cam in the distributer wearing out the follower on the points.

[pmonk]

Just a dumb idea is suppose, but is it possible your centrifugal advance unit may be slipping? I know that mine has a lot of slop in it and I have to be careful to have it in the same place when I snug up the nut. Timing would be way off if it slipped counter clockwise if the nut wasn't tightened correctly. If the nose piece or the centrifugal unit was extremely worn, is it possible for it to slip?

[Duane Ausherman]

Hold the advance in the direction of tightening the nut. It won't slip then.

[pmonk]

thanks Duane, that is what I finally figured out. And after enlarging the slots I was finally able to get the timing perfect at full advance. It did make a difference in fuel mileage and the old bike runs great at 70-75 mph. I used to go on reserve at 170-180 miles, now going over 200 miles before going on reserve and getting anywhere from 45 to 47 mpg.