Model 8 piston rings

Started by ChrisF, March 26, 2022, 11:02:45 AM

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.

Greybeard

Excellent news, Chris! They are very quick with postage too. Mine were ordered one afternoon and on the doormat the following morning.

Steve
1916 Triumph Model H
1926 AJS G8 500cc ohv
1937 Sunbeam Lion 500cc
1949 Matchless G80S
1952 BSA A10 Golden Flash
1953 Matchless G9
1953 BSA B31
1958 Ariel NH350 Red Hunter
1961 Matchless G80
1961 AJS M31 De Luxe 650cc
1961 Panther M120 650cc
BMWs R100RT - R80 - F650GS
1960 Rover P4

ChrisF

 Called Cox and Turner, chap I spoke to said he had +60 rings in stock for a '34 Model 8, £40 plus VAT plus postage for a set of 3. Fantastic!
Cheers
Chris

ChrisF

Rick and Steve,
                       Thank you both for your replies. I will give Cox & Turner a call.
Cheers
Chris

Greybeard

Give Cox and Turner a ring (ahem  ;) ) Theyve just sorted me out with a set of rings for my 1926 AJS - 2mm rings standard though some clown had machined out the 2nd ring groove (of 4) to 3mm and fitted an oil ring. Totally out of place and a genuine bodge. C&T were able to supply a 3mm compression ring to fit.

https://www.coxandturner.co.uk/

Steve
1916 Triumph Model H
1926 AJS G8 500cc ohv
1937 Sunbeam Lion 500cc
1949 Matchless G80S
1952 BSA A10 Golden Flash
1953 Matchless G9
1953 BSA B31
1958 Ariel NH350 Red Hunter
1961 Matchless G80
1961 AJS M31 De Luxe 650cc
1961 Panther M120 650cc
BMWs R100RT - R80 - F650GS
1960 Rover P4

Rick Parkington

Hi Chris,
This looks to  be a bit tricky. First off,  looking at my old Hepolite books it seems the 1929 Model 80 had an oil control ring and two comp rings but the Model 8 had 3 x 2mm (compression) rings as far as 1933.
The Sunbeam bore is 70mm butt he A10 is just under at 69.989mm, worse than that, the 3650 comp rings are 1/16" thick, which is thinner than 2mm - 1.57mm.
If you are on plus 60 that means the bore is now around 71.5mm. BSA and Norton 350s were 71mm but they both use 1/ 16 rings like the A10.
Obviously Sunbeam were a bit unusual using metric, like modern bikes but equally I don't think anything modern would use a 2mm ring - although 2 x 1mm rings in the same groove might work. It looks like Hepolite did make some 2mm rings but mainly for obscure foreign cars - the closest bet is the Renault 1108cc engine 1963- 66, that has a 70mm x 2mm ring with a radial depth of 1/8" set number LR19090, individual ring numbers TP19054/KTP19055 (K meaning chrome, for the top ring) but goodness knows where you'd find any - especially plus 60 - and for French engine it would be plus1.5mm by the way.
The early Morris Oxford used a 2mm ring but was 73.5mm - which would be too much to gap down I think.

It's important that the rings are the right fit in the grooves to avoid pumping problems so you really need to get this 2mm business right - and there is also the problem of radial depth which may be hard to match. At worst the piston can be modified to widen or deepen ring grooves but it's not ideal.
Sorry not to be much help, hopefully someone else can come up with a solution but for now I'd certainly say it looks like A10 rings are not the answer.
Cheers Rick 

ChrisF

Hello, I am restoring a 1934 Model 8. The cylinder has been re-bored to +.060 & I have an original +.060 Sunbeam piston but no rings. Looks like I need butt ended rectangular 2mm rings. BSA 650 A10 (Hepolite R3560) rings look to fit the bill but can anyone tell me if they are ok to fit to a Sunbeam piston or is there something different about them? The smaller piston that came with the bike had 3 compression rings fitted but no oil control ring (only 3 slots.) Can you also tell if this is correct or should it have had an oil ring fitted instead of the lower compression ring? Cheers Chris