Piston Rings

[s7paul]

Hi All,

My CB500 was bored 0.5mm oversize many years ago.  I haven't been happy with it recently, and have stripped it down.  The piston to bore clearance is more than I'd like and compression was well down on 2 cylinders, so I've decided to get it taken out to +0.75.  I've sourced a set of NOS pistons and 2 sets of Honda rings from an eBay seller, but had to get the other two sets of rings from DSS.

My concern is that the rings from the eBay seller are different to the DSS rings.  The top ring looks the same. The second ring of the eBay set has a step in one side (so the outer part of the ring is thinner).  The oil control ring is solid, whereas the DSS rings are 3-piece.

So, my questions are:

Are the eBay rings REALLY old stock (before 3-piece oil rings became the norm)?

and

Would the eBay rings be OK to use?

Any/all advice would be appreciated.

[s7paul]

Thanks very much.  That's interesting, as mine came from..........Stoke!  And yes, the part number on the box is -014.  If anything, I was more bothered about the step in the second ring, as it's something I hadn't seen before.

The received wisdom on t'internet seems to be to bore .0008" to .001" larger than the pistons.  At the moment, I can get a .0025" feeler down the side of some of the pistons (it's fairly tight, but even so).

[ka-ja]

I was always told that the compression ring with the outer edge step went in the top groove, the step was to avoid any small wear step in the cylinder bore top.

[s7paul]

The top rings are identical in both sets (with a small chamfer on both outer edges).  The position of the T mark on the stepped rings is such that the step is on the bottom side when fitted.

Edited to add: A bit of searching has revealed that the stepped second ring is called a Napier ring.  I'd never heard of it before.

[ka-ja]

Just had a look at some nos Honda CB72 rings, looks like top ring champhered edges, middle ring outer step to the bottom, both rings marked tp  for top, my original thoughts were for "Cord" rings for worn cars. And yes the two top rings are different colours as already stated.

[s7paul]

Yes, ka-ja, that's what mine are like.  So if yours were for a CB72, mine must be really early CB500 rings.  I think I'll try to source another 2 sets with 3-piece oil rings.  I'd feel more comfortable knowing they're the later type and all the same.  Thanks for the info.

[AshimotoK0]

I have these two sets on ebay at the moment (3-piece  oil rings)

£10 total  for the two sets plus post to you if any use.

https://www.ebay.co.uk/itm/143585827517?ssPageName=STRK:MESELX:IT&_trksid=p3984.m1555.l2649


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[s7paul]

Permission to kick myself!  I hadn't seen the last message, and have now ordered some (and they were somewhat more expensive!).  Thanks very much for the offer though.

Were yours on eBay last week, because if so I didn't see them when I bought the ones I've got now?

[AshimotoK0]

Permission to kick myself!  I hadn't seen the last message, and have now ordered some (and they were somewhat more expensive!).  Thanks very much for the offer though.

Were yours on eBay last week, because if so I didn't see them when I bought the ones I've got now?

No probs ..They have been on there for over a month ! and a month earlier on in the year ..

[Bryanj]

Ken, if yours is a later 500 the 550 cylinders may go straight on, or cheat and bore the 500 to 550 pistons

[AshimotoK0]

I’ll take them Ash if that’s ok, just add them to the cover for when I pop over. Not knowing what state my barrel liners are after 30 years I was thinking it may finally need a rebore, either that or fit some 550 barrels but that involves widening the crankcase opening IIRC

Yea that's fine Ken.....I ended the listing.

I also checked out some 3-piece oil ring ---383--- rings and apart from a later style of spring/separator ring as on the CX500 .. they are the same as 500's. They fit the 330 pistons which also fit a 500/4


https://www.ebay.co.uk/itm/143570835008?ssPageName=STRK:MESELX:IT&_trksid=p3984.m1555.l2649


My friend also has these on eBay.


https://www.ebay.co.uk/itm/Honda-CB500-4-NOS-piston-rings-13021-323-013-first-oversize/153864850256

[Trigger]

Ken, if yours is a later 500 the 550 cylinders may go straight on, or cheat and bore the 500 to 550 pistons

By the time you have gone to all that trouble, you may as well put a 550 engine in, if the bike is that far away from std   

[Bryanj]

Its the 605(592) that standard 500 liners wont do Ken, 61mm nominaly

[AshimotoK0]

I don't like the 550 engine in a 500 frame Graham. The bigger clutch housing interfered with the rear brake lever, tried it before, didn't like it so went back to the 500. It's far away from standard yes but it's all that era Honda parts, I just prefer to upgrade the stuff Honda should have got right in the beginning 

Always thought the 500 liners wouldn't bore out to a 550 piston Bryan. Well not safely anyway. My engine number begins 20249** not exactly sure how that sits in the engine number range.

Not sure if first over will be enough Ash, most likely would be before buying I'd prefer to see and check first, at 3rd over your pretty safe it will clear at that.

Yes agreed .. I just got away with +0.25

[Trigger]

I don't like the 550 engine in a 500 frame Graham. The bigger clutch housing interfered with the rear brake lever, tried it before, didn't like it so went back to the 500. It's far away from standard yes but it's all that era Honda parts, I just prefer to upgrade the stuff Honda should have got right in the beginning 

Always thought the 500 liners wouldn't bore out to a 550 piston Bryan. Well not safely anyway. My engine number begins 20249** not exactly sure how that sits in the engine number range.

Not sure if first over will be enough Ash, most likely would be before buying I'd prefer to see and check first, at 3rd over your pretty safe it will clear at that.

I can't see that. I have a 550 motor in a 500 frame and there is no interference of the brake pedal. The 550K0, K1 and K2 had the 500 frame and brake set up