G80S piston rings JP piston

[56G80S]

I got the barrel back from T&L and thought I'd put the piston rings on the new standard JP piston to fit into the relined barrel.

But having read the little instruction leaflet, I can't see any indication which is the top compression ring and which is the second. There are no chamfers or markings. T&L advised that the rings usually come gapped already but I think I'll check; what gap have others used when doing this (thou per inch diameter?)?

I usually fit the rings using three thin "tin" strips to ease the rings down as I don't do it often enough to spring them down with my fingers; what do others do?

I also don't have a large enough piston ring compression tool (have a pair of smaller ones) for fitting the piston into the barrel and have used a cut open large tin with a jubilee clip; am I just a bodger although I am careful to make sure there are no burrs / sharp edges. Need a tool as my finger ends can't manage the job.

Views welcome, don't be afraid to correct my methods.

Johnny B

[thornebt]

I always feel very nervous fitting piston rings. It's a job I really don't like, If I had collected my barrel from T&L I would have asked them to install the piston and rings in the barrel for me. But you probably used a courier.

I bought a piston ring compressor from Ebay and it was quite cheap. I still found that I needed to give the piston crown a gentle tap with the wooden end of a hammer just to get the rings to enter the bore.

Cheers. Bruce.

[clive]

Johnny buy one of the piston ring compression gadgets the correct size for a 500. They are not that expensive and you will wonder why you b***ered around with tin strips, makes the job so easy and certainly no taps from a Hammer required.

[56G80S]

Both

Thanks for the advice. I'll take a look at the ring compressors a bit later. I think I'll go that way. I found them really useful when working on a twin (not AMC).
Just for clarity, what I've done previously is slice open a can large enough to take the piston and use that to compress the rings to fit the piston into the bore; using plenty of oil.

You'll laugh but I have previously suspended the barrel from the top tube. Then raised the piston into the bore rather than have the piston at BDC supported on rods across the crankcase mouth and lower the barrel onto the piston; I find it easier to judge the force being applied and manage location moving the lighter weight.

I use three thin strips to spread the rings to get them onto the piston nothing to do with entering the piston into the bore.

Still have a problem with which of the two two compression rings is the top and which the bottom and whether there is an up /down side to either of them. Think I'll ring T&L.

Johnny B

[Dave T_LAPSED]

Since my first bike I have fitted the piston, then the barrel, sweating and afraid I'd break the rings!
Then I recently read to fit the piston into the bore, easy peasy on the bench, rings squosed into chamfer, doddle.
Next slide barrel onto studs but support on wooden block(s) leaving enough distance to raise conrod and fit gudgeon pin and circlip (stuff crankcase mouth with clean cloth, it's really annoying fishing the "pinged' circlip out of the depths!)
Job done, really easy, now how come someone with my huge intelligence never thought of that before?

Hope that helps.

Dave.

[REW]

I have always fitted rings to piston by hand - opening them up enough to go over the crown and then in stages down into the groove/s. To get over the first groove I take the ring to just above, then spread the ends enough to go below the groove so the ring is angled over the groove - it can't fall in then. As for fitting the piston into the barrel, again I squeeze the ends together and the chamfer on the barrel is enough to keep the ring from opening up. And yes, hanging the barrel off the top tube works very well so you can lift the piston up and in. Dave's suggestion sounds good too - well worth a go.

[Andy51]

Johnny, I fitted a JP piston in my 18S about 10 years ago and don't recall any instructions on which ring is which - I don't think they are tapered or chrome plated, but check with JP. Andy

[56G80S]

Cheers

Been away for a few days but thanks.

The Silverline piston ring compressor arrived - about £6 or so through Ebay and I reckon it will make the job a heck of a lot easier.

Johnny B

[Expat]

Will never forget that as a green apprentice a long time ago, my foreman advised me to fit piston rings by opening them over the piston using nothing other than a strip of rag over each end of the ring.

He was a clever old sod and i could not believe how that stopped me, as a seventeen year old Fanny Barnet owner, breaking rings every time i tried fitting them!

Something to do with having finer control over force applied.

Regards, Steve.

[pkr87]

When I was an apprentice(1960ish) I was trying to fit new rings to a 7 inch diameter piston from a Dennis lorry. The rings had cost an apprentice's week's wages and try as I might there was no way these were going to fit without breakages, even the crafty old foreman (he was probably all of 40) could not make them fit. We phoned Hepworths, the piston makers, and a rep came along and flicked the rings onto the pistons by just pulling the rings open with his fingers and sliding them onto the piston. I have been fitting piston rings that way ever since, the only thing to make sure is that the piston is firmly held so that you can slide the ring straight on.Paul