I'm finding that the heat insulating washers take up all the depth of the locating step in the valve guide such that the valve spring cups don't necessarily locate centrally.
Does this matter, or will they self-centralize? It's worse with the inlets, which have 062725 750 Commando guides, as recommended by Andover Norton. I believe it may be possible (but undesirable?) to dispense with insulating washers on the inlets.
I've found with more than one set of valve springs that the end of the coil is slightly too wide to fit snugly down into the cup and needs to be ground down slightly. Is this common? Or I am fussing too much?
Perhaps your cups are inco…
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The cups are the originals…
The cups are the originals that have been in place for the 42 years I've had the bike, at least.
I've got another cylinder head (pre 1960) lying around and the shoulders on the guides are much deeper so there's plenty of room for washers and cups. So the problem lies with replacement guides and/or washers. The 750 Commando 062725 inlet guides have less depth of shoulder than the 063527 exhaust guides replaced at the same time, both from Andover Norton.
The washers are 2.2mm thick, which I have a feeling is thicker than the old ones. I tend to hoard old junk so maybe I'll be able to find them.
I tried rubbing a washer down to about 1.5mm thick and that gave just about enough exposed shoulder to allow the cup to locate, so that seems to be the answer, assuming it's not going to affect the install height of the springs significantly. It's not as if the new springs are all exactly the same length anyway, so I can't believe it's critical.
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Previously rob_bradley wro…
Previously rob_bradley wrote:
Had the same problem with guides form Norvil !!!!!!!
send your original as an example for them to match as the best way forward
regards John
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Perhaps your cups are incorrect. Or the washers are too thick. These washers are usually about 2mm thick. Generally the shoulders of the guides sit inside the heat washers with about a mm clearance. This was common on all the standard Dommie engines and I believe the 750 Commandos.
Some Commando guides (850?) have no shoulders....a circlip acting as a stop. I guess these rely on the spring self-centralizing.
You are correct about being able to omit the inlet heat washers but most sensible people keep them as excessive heat will eventually soften the valve springs and/or you are also losing some of the spring tension which might allow valves to float at high revs.
Spring ends can vary a little in diameter. I usually just bung then in and let the camshaft loading push them into place. Though this does make dismantling them a bit tricky during the next rebuild. Grinding will work as will heating and bending but there is a slight chance of damaging the spring.