Compression every other kick???? Schleicher Cam question.

[therealkennyboy]

I know I always have to remove/clean the idle jets several times in getting an old bike going again (sometimes even after just sitting for a few weeks). Maybe the quick ride got some sediment moving around? Granted your aggravation/frustration index is likely pretty high right now, but the fact that you got 'better than before' performance on your quick spin is certainly encouraging--you've got that to look forward to at least.

Maybe try changing your point gap a bit? I believe tighter advances the ignition and wider retards it (try it both ways!). The spec is less critical in a two cylinder engine, and with the altered cam profile maybe you need earlier or later spark? Just a thought.

Very frustrating, keep at it.

[schrader7032]

Yes, I'm familiar with the butterheads. I've just never heard anyone say that the spark plug ovaled as a result of that. What I have heard is that the valve clearances aren't stable as the head deforms.

The butterheads were more of a mid 60s problem due to the metallurgy being used at the time. I didn't think that it was happening in the early 1960s with the R50S was being produced.

[1967 R502]

Maybe the quick ride got some sediment moving around?

That’s very logical, and I thought about that too, however the issue is not that it runs poorly, it’s that it won’t start. There is plenty of gas in the combustion chamber as evidenced by the very wet plugs.

Under these conditions I would expect something: a pop, a gurgle, some ignition, but there is nothing.

[Daves79x]

If the coil is original - change the coil - it will run. A bad coil will show spark at the plugs, but not enough to run.

Dave

[1967 R502]

If the coil is original - change the coil - it will run. A bad coil will show spark at the plugs, but not enough to run.

Dave

The coil is emerald island. Works fine

[1967 R502]

The butterheads were more of a mid 60s problem due to the metallurgy being used at the time. I didn't think that it was happening in the early 1960s with the R50S was being produced.

The mid-sixties is when the issues emerged, Duane says the issues were a result of manufacturing process changes in 61-62. My bike is from 62. Of course this is just Duane’s idea but could be right or wrong with no detailed timeline given

The heads had previously been worked on by Randy Long, and had all kinds of issues. So.. at least this set are definitely butterheads. Exacerbated no doubt by the R50S being the highest compression BMW bike of the era.

Regardless, there appears to be some leakage past the plug. I don’t know how to explain that other than the holes are no longer round.

[1967 R502]

The butterheads were more of a mid 60s problem due to the metallurgy being used at the time. I didn't think that it was happening in the early 1960s with the R50S was being produced.

The mid-sixties is when the issues emerged, to the public. Duane says the issues were a result of manufacturing process changes in 61-62. My bike is from 62. Of course, this is all just Duane’s ideas, and they could be right or wrong and no detailed timeline is given.

The heads had previously been worked on by Randy Long, and had all kinds of issues. So.. at least this set were butterheads. Exacerbated no doubt by the R50S being the highest compression BMW bike of the era.

Regardless, there appears to be some leakage past the plug. I don’t know how to explain that other than the holes are no longer round.

[Daves79x]

I do not think the R50S head would be butterheads. They and the R69S heads were unique and as far as I know, never suffered the problem. Your heads may have had myriad problems, but I don't think the butterhead issue was one of them.

I assume you have had the magneto apart, timed it, cleaned all the mating surfaces for a good ground, tested the rotor for good magnetism? Static timing right on the S mark with little differential timing? Advancer working properly and seated correctly? I see where someone mentioned cleaning the points, but never saw that you checked that, but might have missed it - a lot of reading here.

Dave

[pkrpkr]

Perhaps it would help to make a timing diagram of the valves and ignition point.
You can mount a degree wheel on the front of the crank, measure valve lift with dial gauges. For the points I use one of those Aircraft Spruce boxes to not have to disconnect the points for measuring when they open.
It might give you an idea if the ignition timing is plausible relative to 4 cycles of the engine.
How are you measuring that you have spark? With the plugs outside of the engine or with a stroboscope light with the plugs in place under compression during kickstarting?

[Seek]

I do not think the R50S head would be butterheads. They and the R69S heads were unique and as far as I know, never suffered the problem. Your heads may have had myriad problems, but I don't think the butterhead issue was one of them.

At the moment I am struggling with a R69S head from the Butterhead period. It has dropped the exhaust valve seat twice in very short order. The guy who does the work suspects the butterhead problem. I don't really know, it doesn't have the other typical butterhead issues.

Anyway, the problem with the aluminum alloy was general because of new regulations. But the R69S head was better designed with larger cooling area. So maybe they didn't get as hot as the R60/2 ones? Thus less problems?