I rode the bike to Mumbles (Swansea) yesterday a round trip of around 40 miles, the longest ride since getting the bike running again just over a week ago. The journey there was perfect. Cruising along the duel carriageway at between 50 and 60 mph with a big smile on my face. The return journey (after 3 hours of fishing off Mumbles sea wall) was going equally as well as the journey to Mumbles but about 3 miles from home the bike suddenly began to lose power, then as soon as I pulled in the clutch the engine cut out. I pushed the bike to the safety of a lay-by and feeling that the engine was rather hot I let it cool down for 20 minutes. When I gave it a kick it fired through the carb and there was a heavy kick-back on the kickstart. Several more attempts brought the same result so no other choice but to call Carol Nash Assistance and get the bike back home on the back of a breakdown lorry
This mornings examination shows that the spark is now occurring well after TDC! I removed the points to see if the little "Key" on the points brass backplate had broken off but all was intact and points functioning as they should but opening at the wrong time. My conclusion is that (probably) the magneto pinion cog has either slipped on the tapered shaft or some teeth have come off one or more of the timing cogs. Will post more after I've gained access to the timing pinions. Has something similar happened to any of you guys?
I've taken off the outer timing cover, Dynamo drive sprocket and chain, Magneto drive with Advance and retard. Removed the 4 recessed bolts that hold the inner timing casing but the casing seems solid and I'm loathe to hit it in case I break off part of the casing. Does the oil pump and worm drive need to be taken out in order to get the inner casing off?
Would be glad of advice guys
Cheers
Dave
Was there any sign of damage to the advance/retard unit teeth? If not, there may not be any need to remove the inner timing cover, although I have one available should you still want to remove it and have any problems/damage removing it. Once the four screws are removed, it should come off, although it may be sticking on the locating pegs. Removing the oil pump/worm drive would make it easier to see what is happening, although from memory I don't think it is essential to remove them (if anyone who has stripped down a FH recently disagrees, do say so!).
I would put my money on the timing slipping, what do the tapers on the magneto armature and A/R unit look like? Perhaps a very careful lapping of the two surfaces with fine grinding paste would help, but you must be sure to remove every trace of the paste afterwards, removing the magneto from the bike would make this job easier.
The only thing that otherwise could alter the timing is if the woodruf key(s) on the crank pinion or cam pinion have sheered and allowed the pinions to move, but I would have though this would affect the valve timing and possibly result in a valve hitting a piston. To check this, you would need to remove the inner timing cover.
Thanks Pete, Teeth on the magneto advance/retard are fine as are the teeth on the Idler cog but without taking the inner cover off I cant check the other cog. I'm not willing to risk damage to the inner casing so I'm taking it for granted that all is well with the cam. I'm reasonably sure that the advance/retard mechanism has slipped on the tapered shaft and will do as you suggest and give it a bit of a lapping. Turning the engine via the rear wheel shows that the valves are operating as they should ie both closed at around TDC on the firing stroke. Which again leaves the original opinion that the A/V has slipped.
Thanks again for the advice
