fixing loose valve guide

[c wastellParticipant @cwastell25217]

Thanks for all your knowledgeable replies, gents. You have convinced me to forget about a quick fix and go for the over-size guide. Unfortunately, all the spares have to come from Italy which complicates and slows down things down somewhat. I have a good engineering company, Cerney Engineering near Swindon, I would not attempt this myself.

[the artfull-codgerParticipant @theartfull-codger]

A lot of yrs ago I had a 500cc gold star & the exhaust valve guide was loose in the head [bronze guide,alloy head], I got some copper sulphate & a piece of copper ,cleaned the guide & corked the ends & copper plated it, never had anymore bother.

Graham.

[old martParticipant @oldmart]

You could take the valve guide to an electroplating firm and they could plate up the relative part while masking off everything else. Then the od could be carefully turned down to the correct interference fit. Turning using a very sharp tool and taking minimum depth cuts. The head would best be heated when fitting the guide.

[c wastellParticipant @cwastell25217]

I had to order a new valve for Italy so at the same time ordered a replacement o/s valve guide. The supplier is a specialist only in these old Guzzis so I will be interested to see if the new guide is bronze or iron.

[old martParticipant @oldmart]

The main difference is that bronze must be lubricated and iron not, that is why most iron guides on more modern vehicles have seals to keep oil from getting into the cylinders and coking up.

The last bronze guides I had were on Royal Enfield twins.

Edited By old mart on 30/05/2022 21:23:34

[blowlampParticipant @blowlamp]

Posted by duncan webster on 28/05/2022 01:47:30:

Having had awful trouble trying to drill ally bronze how do you do it? It seems to shrink onto the drill and seize. Gave up eventually

Try using a split-point drill, like the one on the left.

Martin.

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