Wear on Bevel Shaft

[Duccout]

Has anyone found a way of dealing with wear on the bevel shaft where the two halves meet? My own Strada has a lot of play in the coupling, resulting in lots of backlash at the camshaft, and the replacement bottom bevels that I have just received are also very worn here. I recall Nigel saying that he welds this area with stellite and regrinds it, and I remember Kev (a name from the past!) saying that a piece of feeler gauge can be inserted, but I doubt that this fix would last very long, although perhaps some hard shim would (if it could be cut to size).

Colin

[George]

Can't help with your problem Colin, I piece of hard shim might work for a while but the stellite idea sounds more permanent. You are certainly having a hard time with the Strada

[Duccout]

No-one said it was easy! It keeps my limited brain occupied.

Regards,

Colin

[Jordan]

The factory spare parts manual shows various undersized versions of the sleeve that goes around the semi-cylindrical coupling.
It doesn't seem to be an ideal solution to wear at the flat faces, but a wrongly-selected sleeve could result in unwanted play?

[Duccout]

In my experience, the undersized sleeves only work on an unworn shaft. My 900 came new from the factory with play in the joint, and fitting the first undersized sleeve cured it, but I think that once the flats have worn then something needs to be done to restore the wear on the flats. I'm guessing that wear occurs BECAUSE there is play in the joint, allowing the two gears to fret against each other.

Colin

[Geordie]

I have seen this joint referred to as an Oldham coupling on this site. I doubt that correct: it does allow for shaft installation and operational length changes but not misalignment. All parts should be a sliding fit, I expect. I'm not sure how the two flats would fret enough to wear. If they fret then so could the tube. My engine showed signs of poor top end lube but no wear at that coupling. Could it have been initially assembled with too loose a sleeve? Do the diameter and radius measurements indicate wear of the flats?

[Duccout]

Yes, there is a distinct step at the worn/unworn area of the flat. I would imagine that poor assembly (or if you want to be brutal, poor machining) when the engines were built is the culprit. Any play at the joint will allow the two halves to wear against each other as the bevel gears are loaded and unloaded by the valve springs. Things are not helped by the actual contact area of the flats only being about half of the available depth - the bevel shaft could have been 5mm longer to give better contact.

Colin