WD 16H magneto cam

I had the timing set advanced more than 7/16th and less advanced that 3/16th but the best operation seems to be around 5/16th BTDC.

The symptoms are a general lack of power in all gears with the engine not wanting to push beyond 45mph in top gear and even the slightest incline causing the revs to drop off requiring a change down on the gearbox.

All seems well with the fuel mixture and jetting, the plug looks perfect, light brown deposits and no glazing or soot. Also the bike runs best in 3rd gear, when the revs pick up and making the engine a little thirstier, and various positions on the air lever have little effect, so fuel wouldn't seem to be the problem.

I don't really want to start mucking around with valve timing, it "feels" so much like retarded ignition, but advancing doesn't cure it!!

I have found a dealer who has an "R" cam which he is posting to me tomorrow, I am hoping it will solve the issue, but was interested to know the reasoning for L and R cams. I was assuming that with a single and one spark per rotation of the cam it wouldn't be that critical, unless the dwell angle is seriously affected? I will post the result once I have the cam fitted, fingers crossed.

Previously David Cooper wrote:

I hope someone will know about the L and R - if not I'll take the cover off mine and look. But I'd rather not as the cover is a b***** to remove as you probably know - it's a case of turning the engine round and round until it's 'just so' - and try not to jam the thing and do some damage. But the relatively gentle 'up' ramp with the much steeper 'down' ramp afterwards should be visible.

What timing are you using? Mine runs well now it's 1/2 inch BTDC on full advance. I've seen both 3/16" and 7/16" in different books.

The other issue I had was the top arm of the contact breaker not being square on top of the lower contact but skewed sideways a bit - as a result of the above-mentioned problem replacing the cover.

Cam arrived today! I have fitted it and the bike starts much more easily and the advance lever actually seems to have an effect on the running of the engine now, so signs are promising.

Will have to wait for tomorrow for an actual test ride though, roads down here are like a river right now.

Photo attached of the R and L cams side by side for comparison.

Thanks Richard, just been on first test run with the newly adjusted magneto and the improvement is clear. Top speed now around 60mph and the pick up has been transformed. In fact it is a little bit hairy on those girder forks on our wonderfully maintained and pothole free roads!

The bike is now idling too fast so I think some tinkering with the carb will follow,