I'm well on the way with my jubilee restoration but need some advice on my barrel situation . I'm thinking about getting them re lined . The reason being is that they are standard barrels ( I think ) the pistons I removed are stamped standard 60mm but the bores on the barrels are different. One measures 60 Mm and the other is 61 mm . I have bought standard rings but even in the 60mm barrel the ring end gap is way to big 0.73 and obviously much bigger in the 61 mm one . It looks like the engine has been apart previously as the pistons were spotless with no carbon deposits and no gaskets in the block or valve covers . I think re lining would be the sensible next step . Any thoughts on this please . Cheers Graham.
Jubilee pistons
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Pistons JUBILEE
My pistons are stamped STD ID 10 and the other one STD ID 3 and the letter A . Any ideas ? Thanks Graham
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Thanks for your advice Peter…
Thanks for your advice Peter . That makes more sense to me now .
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Pistons for Jubilee will all be marked on the crown. All carry " 60mm" lightly engraved. Also one of STD, +. 010, +. 020, etc.
A piston fitting a 61mm bore will carry markings 60mm +. 040.
If your pistons are indeed spotless and undamaged with good ring grooves, then I would have a go with new rings which are sold to match the size (oversize) engraved on the piston crown. You may have to buy two sets if your bores are different overbore sizes.
Your good intention of recovering the cylinders by lining will be both difficult and expensive.
I would not worry about one bore being larger than the other. Your ring gap in the smaller bore of. 73mm suggests to me a new STD ring inside a 60mm +. 010 bore.
I am presuming you are not out for a race, but looking forward to happy bimbling around in the sunny weather sure to come soon.
Peter
PS. Edited my 66mm where it should have been 60mm.