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Can I re-ring pistons a second time? #494685
06/19/13 6:23 pm
06/19/13 6:23 pm
Joined: Nov 2007
Posts: 11
New Jersey, USA
J
JohnP Offline OP
BritBike Forum member
JohnP  Offline OP
BritBike Forum member
J
Joined: Nov 2007
Posts: 11
New Jersey, USA
Did a top end on my MkII 850 and also removed the barrel. I have about 10,000 miles on the second set of rings on the stock pistons (installed gasp, 30 years ago!). The cylinder bores are round and still measure within stock spec. Questions: 1) with 10,000 miles on the last set of rings, are new rings likely needed or not?; 2) if so, can the stock pistons be re-ringed a second time ( I heard somewhere that pistons should not be re-ringed a second time); 3)If so, recommendations for ring brands to use or avoid? If re-ringing again is not recommended, any recommendations for replacement pistons to consider/avoid? Thx in advance

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Re: Can I re-ring pistons a second time? [Re: JohnP] #494687
06/19/13 6:29 pm
06/19/13 6:29 pm
Joined: Dec 2004
Posts: 9,375
Scotland
kommando Offline
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kommando  Offline
BritBike Forum member
Joined: Dec 2004
Posts: 9,375
Scotland
Re ringing is fine, 850's seem to run 2 or 3 sets of rings per rebore on one set of pistons. If you need new pistons then avoid the JP pistons, Cycle Craft/JCC/Emgo (all made by the same company) are good provided you fit a good ring such as Hastings, the latest Hepolite boxes contain exactly that combination.

Re: Can I re-ring pistons a second time? [Re: JohnP] #494753
06/20/13 5:35 am
06/20/13 5:35 am
Joined: Jul 2009
Posts: 3,549
Vic. Australia
P
Pete R - R.I.P. Offline
In Remembrance
Pete R - R.I.P.  Offline
In Remembrance
P
Joined: Jul 2009
Posts: 3,549
Vic. Australia
It can't do any harm to fit a new ring set.If the cylinders measure OK (less than 0.005" or 0.006" taper/wear) and the pistons look OK,it will run fine.

Give the cylinders a coarse hone (not much finer than 220 grit),and a good scub in hot soapy water.Spray them with WD-40 afterward and wipe off the excess.The rag should be clean after wiping.Dry ring assembly seems to give the best results,with just a drop of oil on either side of the piston skirts.

Re: Can I re-ring pistons a second time? [Re: JohnP] #494804
06/20/13 5:47 pm
06/20/13 5:47 pm
Joined: Aug 2012
Posts: 620
Oregon
D
Dana_twin Offline
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Dana_twin  Offline
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D
Joined: Aug 2012
Posts: 620
Oregon
Rings tend to "sack out" over many years of being inside a bore, thirty years is a good candidate, but it seems worse in an engine that has not run for many years in my experience. When you get the new rings compare the ring free end gaps (ie as in not installed of course) and you will likely see that the new rings have a larger free end gap than the old, sometimes significant. Having said that there is nothing wrong with having "old" rings in your engine, until oil consumption and blow-by become noticeable perhaps.


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