I have recently started a rebuild of my late brother's AA combination and have a broken piston ring. The piston is marked +030" I have searched online and can only find rings for +020 +040 and +060. I would welcome any advice.
originally the oversize options would have been in ten thou increments so +.010, +.020,+.030 etc up to +.060.
after that a new cylinder, nowadays a re sleeve. so your piston at +.0.030 was possible. cuttting out the odd size options removes half the stock.
if the piston and bore look ok try your local (or national) engineer. mine can usually come up with options.
there are a few classic piston/ring specialists attending classic shows.
https://www.fwthornton.co.uk/motorcycle-pistons
there was someone in the Swindon area
or try a specialist machine shop like Pistonbroke in Bristol.
If you're just going to replace the ring and are OK with a bit of delicate DIY then I'd suggest getting a +040" ring and increasing the gap between the ends using a Dremel with a fine grinding disc to obtain the correct space of 0.010".
Insert the ring into the cylinder, use the piston to push it down squarely to the lower, less worn part of the barrel and then use feeler gauges to measure the gap.
If the barrel is worn you may find that little or no increase is needed. You could also check the end gap of the other rings for comparison. As a rough guide I'd suggest anything over +0.020" would indicate a good degree of wear but remember that these old chuffers are not high performance engines and they can run hot - so I'd probably rather have a bit too much than too little to allow for heat expansion.
Cheers,
Bernie
:) :)
Not a phrase that I really like but at a push you should be able to "get away with" +040" carefully shortened to the same lengthy as your existing ring.
I have had rings made but can't remember the details. I'll try and get back to you if I can find them.
Mike 8) 8) 8)
:) :)
You could try: - Clupet Piston Rings. 01900 818361 Guy named Alan. (This from a friend, no personnel knowledge)
Seriously it sounds as if your bores are already almost +040" may be more even, and that possibly your ring was broken by piston slap, A new ring could easily go the same way within a very short time. The next size readily available is +060". How many miles do you recon it will do from now on. Rebore and piston will not be a lot more than £200 (possibly less with luck) I reckon minimum 20,000 miles. I guess that will set it up for life.
Certainly the way I would be considering. All the best with it.
Mike 8) 8) 8)
Quote from: Mike Farmer on 14 Aug, 2019, 20:22
:) :)
Not a phrase that I really like but at a push you should be able to "get away with" +040" carefully shortened to the same lengthy as your existing ring.
I have had rings made but can't remember the details. I'll try and get back to you if I can find them.
Mike 8) 8) 8)
Quote from: Mike Farmer on 14 Aug, 2019, 20:22
:) :)
Not a phrase that I really like but at a push you should be able to "get away with" +040" carefully shortened to the same lengthy as your existing ring.
I have had rings made but can't remember the details. I'll try and get back to you if I can find them.
Mike 8) 8) 8)
Quote from: BP22 on 14 Aug, 2019, 13:20
I have recently started a rebuild of my late brother's AA combination and have a broken piston ring. The piston is marked +030" I have searched online and can only find rings for +020 +040 and +060. I would welcome any advice.
Quote from: Mike Farmer on 15 Aug, 2019, 10:18
:) :)
You could try: - Clupet Piston Rings. 01900 818361 Guy named Alan. (This from a friend, no personnel knowledge)
Seriously it sounds as if your bores are already almost +040" may be more even, and that possibly your ring was broken by piston slap, A new ring could easily go the same way within a very short time. The next size readily available is +060". How many miles do you recon it will do from now on. Rebore and piston will not be a lot more than £200 (possibly less with luck) I reckon minimum 20,000 miles. I guess that will set it up for life.
Certainly the way I would be considering. All the best with it.
Mike 8) 8) 8)
Mike
Thank you for your advice, I broke the ring removing it and on further inspection reckon a rebore will be the way forward, as during nearly twenty years storage the lower part of the bore has some corrosion. If you can advise on a reputable company to carry this out I would be obliged.
Regards
Brian
Thanks to all for their advice, on further inspection it looks like a rebore will be my best option, the engine has been stored in bits for more than twenty years and the lower section of the bore has some corrosion. I will be looking for a company to carry out the work
Regards
Brian
:) :)
Where are you.
The guy I always use is in Winchester Hampshire. In the past he has done lots of stuff for me. Big diesels, old paraffin tractors crankshafts etc. Latest job was reboring my A50 and line boring A65 main bearings. Always busy but a fairly good turnaround time.
Owlesbury Crankshafts.
Winnal Valley Road (I think)
Winnal Industrial Estate
Winchester
Hants
01962 855969
Mike 8) 8) 8)