Valve seat replacement

Previously Niall Topping wrote:

Hi All,

does anyone know anywhere good for getting replacement valve seats put in?, my local place won't do heads with 'cast in' seats and a well-known classic motorcycle engineering specialist company would only do it if I also had all 4 guides done and bought 4 new valves to be lapped in on their Serdi machine and had the head vapour blasted, which they wanted to charge me just shy of £500 for.

Now I'm not saying the work they wanted to do wouldn't have been worth it but all I wanted was 2 blank valve seats put in to cut myself, they refused to budge on this so I finished up £35 down on postage for nothing done, by the way when I contacted them prior to sending my head they said they might need to replace the exhaust guides as the Serdi mandrel uses them as a guide to centre the cutter, but I still can't see why fitting new exhaust seats should need new INLET guides fitting as well.

So does anyone know anyone who will do the seats only without taking the proverbial?

Thanks to all in advance.

Cheers, Niall

Well Niall the place you need is SEP- engineering Kegworth Derbyshire phone number 01509-673295 they do replacement valve seats and every thing else you may need doing and you find them very fair with there prices, now I hope this helps you or anyone else in the Club , Yours Anna J

Peter Lovell Developments in Smethwick!

I belive all twins post 1962 were fitted with hard seats so unless you have a damaged seat leave it alone. I have run the twin on the road and track and never had any seat problems. Don't fix it if it aint broke and all that.

The Norton Twin alloy heads did indeed have hardened valve seats. The problem is the original valves, used with these seats, needed a form of lube to prevent the two respective surfaces from bonding together and then ripping apart. This originally was a form of Lead in the fuel and later a lead substitute. You could change the valves to prevent this surface bonding problem but this then generally led to an incompatibility with the guide material.....which was usually Austenetic iron. So they needed changing to the likes of Colisbro guides.