A DBD34 had the wrong exhaust cam in it. I got a replacement new 65-2446 exhaust cam with a 65-2442 inlet cam. And I have serviced the GP1 carby, but not sure how many turns out on the pilot screw. I have been trying to use a degree timing wheel to do the ignition timing, however it does not work as it should as per youtube videos I have watched many times. I thought perhaps, I put the cams on the wrong marks, as the exhaust valve is returning to close as the inlet is on it way up, too soon I think, but all cam marking match the shaft markings. So I timed the bike with the rod method to find top centre and adjust magneto with the Tally Ho paper at 11.8 mm before TDC. When I try to start the bike a loud backfire occasionally from the exhaust but no start up. I have tuned the bike previously with the other exhaust cam, but I am at a loss to what I am doing wrong. The cams look set-up correctly, however the backfire and non-run suggests the timing and or cams are out of whack or could it be the GP carby. Has anyone had a similar issue.
Assuming a MO1L mag fitted? Did you set timing with mag set to full advance?
Don't forget that GoldStar cams give a valve overlap.
the Mag is a KNC1...and I have it in full advance. I have tried timing 11.8mm before TDC with both valves in closed position, which I believe is the compression stroke. Perhaps my tappets are et wrong.
The DBD ignition timing should be set to 39º (11/32") BTDC with the mag set to full advance.
Finally I found the problem, I read the manual but did not read it if you know what I mean. When setting the valve gaps I forgot to turn the exhaust spindle fully anti-clockwise, then turn clockwise to set the gap at .006 for the DBD34 spec. Opposite for the inlet clockwise then back anti-clockwise to set a .006. My valve gaps were way off no wonder it was backfiring.
Quote from: Derek996 on 26 Sep, 2022, 09:51
The DBD ignition timing should be set to 39º (11/32") BTDC with the mag set to full advance.
I have been told by a guy who is/has rebuilds Goldie engines for many years, that 36 degrees works best for Clubman cams.