Reworking 1960 G3 cylinder head

Will shortly be reassembling the head on my G3 and fitting a new exhaust valve as the stem on the old one is worn and the sealing area looks bad as does the seat in the head. Would really like to lightly recut the seat before lapping but seat cutter kits seem either cheap and a bit nasty, or too expensive to just use one time. Also the cutter mandrel diameters seem to require sizing before use.

Has anyone faced this minor dilemma and if so, how did you move on to finish the job?
Thanks for any responses.
Steve

Take it to a engine reconditioner, they will cut the seats , and most likely add top and throat cut , and reface your valve if required , it would be nice to see the seat ⅓ down and ⅔ up on the valve . Cheers .

Shelby-Right said:

Take it to a engine reconditioner, they will cut the seats , and most likely add top and throat cut , and reface your valve if required , it would be nice to see the seat ⅓ down and ⅔ up on the valve . Cheers .

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I have a '61 G3 ex-Dutch Army. I would agree about taking the head to someone who does them all the time. You have only one cylinder so it should be put right. Do you have a picture of your bike? These things are slow critters compared to a Commando but a lot of fun on tight woodsy back roads.
Russ

batrider said:

I have a '61 G3 ex-Dutch Army. I would agree about taking the head to someone who does them all the time. You have only one cylinder so it should be put right. Do you have a picture of your bike? These things are slow critters compared to a Commando but a lot of fun on tight woodsy back roads.
Russ

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Here's s pic of my 49 g80 500 , I just haven't got time to do it , I have a car insurance job bugging up my shed , I would like to start it and finish it I wouldn't want it in boxes , i have so far done new devon rims and stainless spokes , got the tank to fit made a stainless muffler , and made a stainless side stand , i bought a spare mag and got that rewound , got motor to sort next , pic of piston at TDC ! ½ down
. Cheerrs

Lovely bike. I had a '51 G3L for a time. The 500s have a lot more power than the G3s. I like the wide tank that keeps my knees from knocking.

Some time ago I picked up a Lucas head light shell. Wasn't sure what it was for but the price was right. The paint has been stripped off and it doesn't have any dents. I can send pictures. Plan on taking it to the show and swap meet in Davenport Iowa end of August.
The numbers on it were MCH56 and a bit of research showed it was for a G3 Matchless. If you know anyone who is need of one let me know.

John in Texas

Hi All, apologies for the very late reply and thanks for all the advice. Just got the bike running after a +0.020 rebore, new piston, rings etc and managed to lap both valves in, the shop that did the rebore didn’t have seat cutters. Bike was originally AFS spec from 1960 but a previous owner had painted black. Otherwise mostly all original in good shape, no butchered fasteners, stripped threads etc. Have fitted 6volt led lamps all round and turn indicators. Now carefully running bike in for c 1k miles.
Batrider, do you have pics of your G3?
Shelby-Right, that’s a sweet looking bike.
Steve

batrider said:

I have a '61 G3 ex-Dutch Army. I would agree about taking the head to someone who does them all the time. You have only one cylinder so it should be put right. Do you have a picture of your bike? These things are slow critters compared to a Commando but a lot of fun on tight woodsy back roads.
Russ

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That is a sweet looking bike. You do very good work.
John