After market ring confusion.

No eBay APP ID and/or Cert ID defined in Kunena configurationBought these rings from Japan and assembled the engine. Never ran great at below RPMs and made a chunking sound below 1400ish. Summer hit and got busy and just now am getting back to the bike

So i did a compression check and got solid 60 all across the bank.....red flag goes off. This AM i took the head off to see if I had bent valves or anything like that. Not so much as a tick mark in any of the pistons or the valves.....good signs so far. No broken rings either. So i moved on and pulled the jugs and found the source of the clunking. The piston skirts are slapping off the bottom of the bores...nothing broke but good and scraped up.

Proceeded to remove a set of the rings from number 1 piston to see how i had installed them and i noticed there are no "R" markings like the manual says to be sure are facing up. I did see that one ring says TOP on it and also that the ring i had on the bottom has a slight bevel on the inside diameter.

Questions are (1) which rind is the first top ring and which one is the second ring..and secondly should the bevel on the one ring face up or down?? The ring marked "TOP" measures 2.66 MM wide and the unmarked one measure 2.88 wide. See the pics and help me be certain the rings are in the right grooves and oriented correctly. The link to Cruzinimages is the ring set i bought.

I can only conclude the rings being installed wrong or in the wrong grooves would allow the pistons to slap...Yes???

Scuffing on those pistons isn't from a ring issue. Very strange. Usually it's the bottom of the skirts that get scuffed up like that, not near the pin bosses. It looks like you have had numerous pistons seize in their bores.

I'm not sure about the rings. The 1981 KZ650 manual suggest the top and 2nd rings are the same. The 750/4 manual shows the top ring is beveled with the notch facing up, and the second is tapered with the wide end down. I'm not sure about those rings you bought though but I've never seen scuffing like that as a result of a ring issue.

Me either Ed. First time ive seen anything like this myself. Im totally at a loss for an explantion. Bore gauge says they are all at 61.98 so they arent worn out bores by any stretch.

What would make them seize up though?? They swing nice and fee on the wrist pins. Never low on oil.

Dont know but I just put the rings back on the pistons inn the following manner. The one that had no markings and the bevel to it is inn the second spot with the bevel facing the crankcase. the one with the word TOP on it is in the first spot with the TOP facing up toward the head. Also, why the low compression with new rings and fresh honed cylinders? Nice 45 degree hash patterns too. doesnt make sense to me.

Anyway I am gonna finish it off tomorrow and do a cold compression check and see if its better. worse, or the same before i go for a start again. And yes I twist the grip full throttle when cranking it over for the compression tester.

Better pics of the pistons and bores?
Steve

Maybe measure the ring grooves in the pistons to see if they are the same or diff.

Need pics of pistons in order (1-4)from all sides,,, looks like #2 did not have damage,, WHY?.. check bores.. size and round (maybe oblong?) low, middle , high, front to back, side to side, where the piston shows wear,, should be some marks on the cylinder wall.. can"t see any marks on rings.. also WHY are the marks on the pistons not to the bottom of skirts.. seems like piston slap would put the marks more front to back than at the spot they are..
Very interesting keep us informed

chuck hahn wrote: I can only conclude the rings being installed wrong or in the wrong grooves would allow the pistons to slap...Yes???

Looks like some side pressure on the pistons. Have you checked your end gap on the rings?
Steve

I don't believe this is a ring issue, the scuff marks suggest that there is something uneven i.e are the bores or pistons perfectly round. If it was overheating the exhaust side would seize first on a good bore.
Looks like compression's were down because the bores were scored, The second ring from the top is the only ring that should have a taper with the wider edge being down, if that was back the front you'd see smoke on acceleration. The piston slap sound was the bores/ pistons seizing,

Op didn't report any smoking, and no burnt oil beneath the bottom oil scraper rings so I think the rings are a red herring.

These were a matching block and pistons replaced in their original bores?

Seizure, either heat or lubrication.. I wonder maybe overheating due to weak mix in 3/4 carbs? was it nailed on full choke when cold?

Long shot but did you make sure the arrows on top of the pistons were all facing forward?