I realise that I am following-up on this rather late, but I am having exactly the same difficulties. I see that no-one posted a reply to your question...adrian.hannam wrote: ↑Thu Mar 19, 2020 5:17 am I have done a survey. Without moving the crank sprocket, and moving the cam by 1 tooth either way, the resulting change is +/- 25deg. According to the notes it should be 13 deg. Why is this?
Bruce Longman's otherwise excellent and comprehensive instructions seem to contain what seems like a red herring to this particular greenhorn, in that the movement by one tooth of the cam sprocket is quoted in terms of cam rotation, rather than crankshaft rotation.
In the instructions, all the fundamental measurements about setting/checking the valve timing are based upon crankshaft degrees.
I had arrived at the same conclusion as yourself; this is what I found:
Setting the valve timing initially using the the line on the crank sprocket and the two holes in the cam sprocket resulted in max. valve lift at 112 deg. ATDC.
I moved the chain on the cam sprocket by 1 tooth and max. lift occurred at 87 deg. (when I was expecting it to be about 99 deg. I was hoping to be able to retard it a little using one of the other keyways on the crank sprocket.)
So, I am stuck with valve timing considerably adrift from 105 degrees, with no way that it is clear to me to rectify it.
I have a new cam (from Iron Horse) with new followers. The cam chain is used (but Bruce says a worn one only affects timing by 2 degrees or so, so not really a major contributory factor. I have a new one on order from Drags, anyway.) It would seem that making a stepped key will only yield a couple of degrees difference.
Did you manage to sort-out your valve timing?
Allan.