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Unmatched Rocker Covers - possible?

Posted: Fri Apr 17, 2026 11:46 am
by sam.arnold
Hi all,

My rocker cover has a chunk broken off where the oil feed bolts on. I believe a brake banjo bolt was used to attach the oil feed to the top of the rocker cover (XTZ660 3YF / 4MY), which is too long. It caused a crack, oil leak, and then finally a chunk of aluminium broke off. 1 inch x 1.5 inch

I have two options and would appreciate advice on whether either is possible:
1) Go to a good welder to get it repaired. I'm worried about it warping causing problems for the cam journal or sealing between the head and rocker cover. (Do I need to remove rockers for this? It seems like a pita)

2) Use a second hand rocker cover. The cam journal is half in the rocker cover, half in the head and I believe that they are bolted up and line bored as a pair. My fear is that oil clearances between cam shaft and journal are about 0.02mm, and that dowels are are machined at best to 0.05mm tolerances (a guess). I could end up with a step, poor oiling, and ruin the cam shaft.

Many thanks in advance.

Re: Unmatched Rocker Covers - possible?

Posted: Wed Apr 22, 2026 12:14 pm
by sam.arnold
For info I swapped the rocker cover for another. (but kept original rockers).

Bike has done 30 miles no problems.

Re: Unmatched Rocker Covers - possible?

Posted: Thu Apr 23, 2026 7:27 am
by donnybach
Maybe not many 660s on here. Looks like you’re the new SME. Glad you sorted it. If they were paired, it’s only because they’d have passed an inspection criteria, probably of clearance or interference fit. As long as the new one has same spec you’d be good.