Well something has to get awkward sooner or later and as luck would have it the cylinder head is becoming just that.
I thought this would be an easy place to start off, given that the bottom end was done before and is unused. I was even thinking of throwing in a couple of new valve springs for the hell of it, but on cleaning up parts I found that I have things to attend to first. The butcher’s bill so far is:
- Exhaust valve + guide
- Inlet valve + guide
- One rocker arm
A badly scored exhaust valve stem...
....and the offending rocker arm.
This’ll set me back the fat end of a ton. Actually that’s not bad value when you think about it. Years ago my old CB550 cost me more than that for just a top end gasket set and four spark plugs. At least I'm getting precision made parts this time.
The bit I never like is changing the valve guides. They have to be knocked out of a heated cylinder head using a hammer and drift. There's something that feels intrinsically wrong with hitting such a beautiful casting with a hamer and a steel rod.
The bit I never like is changing the valve guides. They have to be knocked out of a heated cylinder head using a hammer and drift. There's something that feels intrinsically wrong with hitting such a beautiful casting with a hamer and a steel rod.
On the positive side the head’s ok apart from it needing to be cleaned up. I blew the oil ways through with compressed air and trichloroethylene and some crap emerged leading me to suspect that the top end was being a bit starved of oil. It could have been worse; it could have been not a single.
Bath time!
The rocker box bearing faces appear to be ok despite the scoring on the steel arm. I’m going to get a microscope out for these though, as the alloy could have glass in it. If a plain aluminium silicone alloy bearing is starved and overheats, the alloy gives up silicone which re-crystallises like a set of glass knives against the steel parts running in that bearing. This will end up leaving scoring in the steel bearing face and all manner of bad stuff.
Next is to get a couple of drifts for replacing the valve guides.
