/5 timing

[Jean]

It does sound mysterous...
The only thing to worry about, really, is valve timing causing a burned valve.
But if you file the points plate and get the spark to happen in the correct place, it will minimize that possibility.
Of couse, very late timing (too much retard) is more likely to cause a burned valve, as are tight settings on the exhaust valve.
You said "a spot". The sprockets I have, have a radial line stamped into the surface that is to line up with each other...The line on the crank (small) sprocket is on a tooth, and the line on the cam (large) sprocket is on the valley.
Yeah. Getting back into the "compartment" where the chain is, is a beast of a chore. On my R100s, we had to heat the crank bearing quite a bit to get the cover off...and back ON again. Tricky, to say the least. The book makes it sound easy...it ain't.

[Deleted User 72]

There was a line on one sprocket and a spot on the other, I don't remember which. And I'm not gonna look, either!

Thanks for all your time and comments, Jean.

[robtg]

With the timing mark set at OT, check the pushrod height on the overlap side. If one p/rod higher than the other, the cam timing is off one tooth.---Assuming the cam and sprockets are the correct ones.

[Deleted User 72]

Looks pretty close to me. What say you, robtg?

The paperwork from Max BMW says its the correct sprocket.

[Jean]

OK, but that SPOT business still makes me wonder.
I'll have a look at a replacement set next time I have a chance and see what the marks look like now.
Ha. I see you have the choke mod!! Do you use both sides or just one?

[Deleted User 72]

See my post above robtg's.. I amended my SPOT statement to a spot and a line.

I have the choke mod on both carbs, and use them both about half way on a cold start.

[robtg]

Looks pretty close to me. What say you, robtg?

The paperwork from Max BMW says its the correct sprocket.

Can't say for sure, big difference in the adjusting screws, the split on the rocker support blocks are usually
facing out. They look a little off to me but it may be just the slight angle of the photo. Keep after it, you'll
figure it out.

[RickR90s]

maybe I missed it but you haven't mentioned what the points gap was set at. Should be .014" to .016".

Remember that points gap effects Dwell angle, so at .014" gap, the timing is more retarded than .016" gap. I like to run mine at .014" as this gives me a nice adjustment range. At .016", I find the timing too advanced for adjustment.

YMMV,

RG

[Deleted User 72]

0.016"

My timing error is more than 0.002" on the gap, but it is something to try.

[esman100]

I can see how the height of the rubbing block would affect the point gap and thereby the timing, to a small extent. But, the point gap adjustment is approximately in the middle of its range, before I set the timing.

Having thought of this subject prior to posting here, I could give this scenario much more credence if the position of the rubbing block were off, rather than the height. All of my point sets (5) appear to have the rubbing block in the same position.

I have another set of points bought at the same time from the same source (Hucky) in my '77RS, without this issue.
I don't mean to be contrary, and I'm not too upset since the bike runs so well. I'm just curious if others have seen this anomaly and what they did to correct it, etc.

I know for a fact some BMW points came in with the height of the rubbing block too high and this effects the position of the points plate orientation even when set to .014-.016" gap. I had the same timing symptom that you are getting and I ended up filing out my plate to get close until I figured out the real problem. This was confirmed later by our local dealer after many complaints. I'm not saying that your points are bad, but it seems possible that even though they came from the same supplier, one could be bad. It's easy to measure and very obvious in a side by side comparison. The bad points are approximately 1 1/2 mm taller.