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Hi all,

I have just returned home from a very brief visit to England because my Camel decided to break down coming from the ferry... (I hope this is not common in your country... )
Anyway, when I took one of his lumps off I saw a small crack between the valveseats. From different sources I heard that this doesn't do much harm and I should continue using it. Repairing it seems useless because it will reoccur?

Does anyone have any experince with this?

Hi,

My 350 did this some years ago, and eventually the inlet valve seat worked loose and started pounding into the head. Took a while to go though.
Listen carefully to tappet noise - if it goes quiet and doesn't start or idle well, it may well be that the valve seat is moving and you have lost the tappet clearance.

Unfortunately the only certain cure is a new head.

George.

If it's a 501 engine then this isn't all that uncommon. A GOOD cylinder head shop should be able to do a reliable repair.

The valve seats have to be removed, the crack machined out with a ball end mill and the head built up with weld. New seats can then be fitted.

The following sequence on Guy Croft's website show an extensive repair to a Vauxhall HS2300 race head.

http://www.guy-croft.com/viewtopic.php?f=2&t=552

Bronze based valve seats have an expansion ratio more similar to the Aluminium alloy and are less likely to cause the head to crack. They are also unleaded compatible and being relatively soft give the valve an easier life.

Hi,

Sorry to hear about your bad trip to England.

Cracks between the valves onthe 501 are very common. My first 501 heads were cracked, I had NLM repair them. It was very expensive- £110 plus vat about 5 years ago but I was happy with the repair. They take out quite a lot of material and put in a Siamese seat which replaced all the material between the valves so cracking again is unlikely. 10,000km on and they still look good as the day they were done.

EVguru wrote: Bronze based valve seats have an expansion ratio more similar to the Aluminium alloy and are less likely to cause the head to crack. They are also unleaded compatible and being relatively soft give the valve an easier life.

morini_tom wrote:They take out quite a lot of material and put in a Siamese seat which replaced all the material between the valves so cracking again is unlikely. 10,000km on and they still look good as the day they were done.

Hi,

My engine is a 478. I'll go and see if I can find a shop that can fix these things. Both options sound good, was it £110 for both heads?
About the trip to England, this was the first time I was left by one of my bikes! It was more likely that the exhaust valve was blocked by coalrests (is that the right word?) causing bad compression than the crack I discovered later.
I'll let you know if I have news.

Hans