New member Nick Craddock recently acquired UR 4313 from Bill Piggott. I received the following today from Nick:
"I purchased UR 4313 in Sep 2011. There has been a noticeable noise from the engine, high up and I think it emanates from the valve gear. The level of noise does seem to be getting louder over the last 5 months of ownership. I am reluctant to drive it any more until some investigation is carried out. Removing the rocker cover and turning engine over on the handle, there is a definite click and you can see backlash from the bevel gear drive, with a free movement of about 1 tooth as the pressure is released from the cam follower and the gear jerks backward. ( Not the best description but as good as I can explain the problem ).
Not having any knowledge of OHC MM's, I am reluctant to start stripping the engine down without further advice and knowledge. I am assuming that the bevel gears are keyed onto the dynamo shaft at the bottom and top. I would expect that there should not any movement on the between the shaft and the bevel gear. The engine was rebuilt some time ago but has not covered many miles since. Can you offer any advice and guidance to me please?"
It sounds to me like the mesh of the gears either at the top or bottom of the dynamo could be the issue, but I'd be glad to pass on other thoughts to Nick.
Help needed with OHC engine
Moderators: Ian Grace, Will Grace
Re: Help needed with OHC engine
Badly worn key or worn keyway in the vertical drive ??
Re: Help needed with OHC engine
The description makes it sound like worn bevel gears......... they were the only parts not available new when we rebuilt our engine..... if it were worn keyways you wouldn;t see the gear jump, just the shaft....
Re: Help needed with OHC engine
Does sound like its gear related, from my recent rebuild experience if you have too much end float the dynamo gears will start to come out of mesh and it makes a hell of a racket, Take your dynamo off and check the gears for wear, and while your at it put a feeler gauge between the thrust washer and the main housing and see what your end float is, 4-6 thou is ok. I had a bad noise and my end float was around 20 thou!!!