Valve seat cutting

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Invicta
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Joined: Mon Jan 29, 2018 9:42 pm
Location: Kent , England

Valve seat cutting

Post by Invicta »

Hi, I am overhauling the cylinder head of my 1949 AJS model 18. Amazingly the valves and guides are in perfect condition after a clean up. But due to the head being off for years and the exhaust valve being stuck slightly open there was some corrosion on the valve seat. I have spent hours grinding in the exhaust valve but there is one tiny spot on the seat that I can not seem to get out. Can anyone recommend a seat cutter that works. I am loath to buy one of these Chinese made kits that will probably be softer than the seat. Alternatively can anyone recommend anywhere in Kent that I could get this seat re cut as it will be far cheaper than buying a set of seat cutters. Thanks.
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Rob Harknett
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Joined: Mon Jan 01, 1990 12:00 am
Location: ESSEX UK

Re: Valve seat cutting

Post by Rob Harknett »

The old bikes are not that fussy. Its just one tiny spot. If the seat is re cut the angle may not match to how the valve has been ground.
I would not worry about one small spot that shows up after grinding. You will probably find the bike would not worry either.
g80csp11
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Location: WEST SUSSEX UK

Re: Valve seat cutting

Post by g80csp11 »

I purchased one of the ebay valve seat cutters from India , spot on it works well and has been used on at least half a dozen cylinder heads with no problem usually after replacing valve guides on my Norton 750's ( opps matchless ! ) and a few matchless singles
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1608
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Location: ESSEX UK

Re: Valve seat cutting

Post by 1608 »

I'm with Rob on this. One little bit of pitting won't hurt. The last thing you want is a too deeply cut/recessed seat.
pkr87
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Joined: Thu May 06, 2004 1:00 am
Location: KENT UK

Re: Valve seat cutting

Post by pkr87 »

It depends what you call a tiny spot. If you have a line of 'nicely' ground seat of at least one or one and a half millimetres preferably on the exhaust port edge then unless you start racing the bike you should not have a problem. As 1608 says grinding away a seat too much can be a worse problem
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Rob Harknett
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Joined: Mon Jan 01, 1990 12:00 am
Location: ESSEX UK

Re: Valve seat cutting

Post by Rob Harknett »

I agree with avoiding " pocketing " the seats. Also in leaving well alone. I have known so many people that have fitted new valves, guides and seats. Then get problems with valves sticking, guides coming loose and seats turning.
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