My recently rebuilt 44 WM20 has developed an unusual screetch/high pitch chuffing noise coming from the area at the back right side of the engine, i thought this was an air leak of some sort but after spraying carb cleaner on all joints it doesnt seem to be. What i have noticed though is my magneto is shaking so i suspected the seal in the timing case could be turning(it wasnt the best fit). So i have removed the timing cover and with the nut/gear still fixed in place but with the mag strap loosened i can slide the mag forward/backward a few mm. Is there a way to shim it back to take up the slack and hopefully stop it moving? Or am i missing something completely, the gear fits on the taper nice and doesnt seem to be slipping so im assuming its fully seated, side note this has only just started to happen the engine has been run for no longer than 30 minutes in total after rebuild. The seal behind the gear is a modern rubber seal and the mag has been recently rebuilt.
The oil seal 'seals' on the shoulder machined onto the back of the mag drive gear...With the straps loosened you would be able to move the magdyno a little...However, you noted that your mag is 'shaking'...It shouldn't do that with the mag straps fully tightened...The noise you can hear is probably air (crankcase pressure) escaping past the seal if the mag (and gear) is moving about on the platform...With the straps loose push the magneto as far as it will go towards the timing side, taking care to ensure it is sitting flat on the mag platform whilst doing that...Then fully tighten the mag straps...You should not be able to move the mag at all once thats done...Finally, start it up, note the results and then post back on here....Ian...
So turns out the bolt i have has quite a large head which fouls the corners of the mag strap, in short it was tight enough much better now doesnt move but the noise is still there so unsure on the effectiveness of the seal but it does sound more like its coming from the carb/head area. I will try to video this tomorrow and upload
Is the bottom of the mag and the mag platform flat and not worn as they usually are? Did you check to see if the mag gear has a tiny bit of clearance with the gear that drives it? If there is not enough clearance it will put a big side load on the bearings and destroy the bearing insulating cups. Did you grease the dynamo clutch as many put them together dry which is wrong? Does the dynamo turn easily?
My guess, you have dynamo problems and the clutch is not greased and slipping which is making the noise. Again only a guess.
Regarding Bruce's suggestion about the dynamo. You can slacken the clamps and move the dynamo out of mesh about 1/2", retighten clamp and run the engine to eliminate the dynamo. Ron
Great suggestions, the dynamo has been untouched for more or less 50 years i only had the mag rebuilt, i opened the dynamo up and sprayed some electrical contact cleaner in and it turns freely but i will try what your suggesting Ron and pull it out of mesh and see what happens didnt really think about that
The dyanmo wasnt at fault, but there is oil staining where it meets the casing so i assume it is the seal behind the mag securing nut letting crankcase pressure past just not had time on the bike since last week so things are moving slow
