i'd love to hear responses to this.. paging @andrewstclair

i currently have my top end open and about to button up as parts arrive.
i had some concerns regarding the piston rings as well but this is one area
my old man does not have much experience with directly.

any info would be greatly appreciated!

i would suspect if you really need to get into the rings, you will have to go through the bottom :dunno

 

you can slip the pistons in through the top. you use an actual tool called a ring compressor thats designed for just that. if you try to do it by hand you usually chip the rings if not suuuuper careful so i don't suggest it and its a lot harder but it can be done. the ring compressor is basically a piece of sheet metal that wraps around the piston with a clamp system around it that squeezes the rings down and you slip the compressor in the edge of the barrel and tap the piston out of the compressor into the cylinder.the bottom of the sleeves are usually chamfered so its easier to do by hand but a ring compressor is still nice.

once you have the head off, the cylinders just pop off so you could just put the pistons in from the bottom then set the barrels back on with the pistons in. to do any of that you have to have the oil pan off and enough stuff removed to get to the connecting rods to remove the bolts and slip them up. you can remove the barrels in place with the motor in and remove the pistons from the rods, replace pistons or rings and reinstall them then slip the barrels back on but its all by hand you have to be careful and it helps to have a buddy. i don't suggest this either I'm just saying in a pinch the possibility to do it this way does exist. i can't stress enough how important it is to get the pistons in the right way or else you bend the valves because the depressions for the exhaust are smaller then the intakes so they hit the pistons if they are backwards, this was even worse with the older 5 valve motors.

as for the rings sticking, are you using race fuel? are you having the bike sit long between uses?

what else are you worried about with your rings bacchus?

 

what else are you worried about with your rings bacchus?

excellent response!! thank you sir, some of it was curiousity but the rest i'll pm.

probably easier to explain over the phone anyway.. we had a tiny little oopsie and dad didnt have the 'knowledge'
on hand to apeace our minds.. the one thing he had no clue on how to is actual removal, install procedure.. its not
something he touches for the most part. Its been too long since he'd done it on a car.

chances are back in the day they didnt use a special tool, but he just couldnt remember, so it left a small ? mark for our conversation..

then Dropped the engine to put the "new" head.
Tried running that, and it didn't start. Then realized all the exhaust valves had zero clearance. .

yup.. classic case of tight valves. i knew it was valve adjust time when i had to keep throttle
on for a minute or so to let engine warm up before it would stay running on its own.

I stopped riding it at end of that season (2015) and now doing headwork etc to get her back on the road. :yesnod

 

Thx @andrewstclaire

Seems I have to do complete teardown. That's the only way to get he rods on and off the shaft.

I was asking about inserting the rings/piston into the jugs from the bottom, but without taking the rods off the shaft (basically with the engine intact). But thinking about it now, it sounds like a crackpot idea.

On the fuel, I'm using regular petrol. On the first engine, the bike never even started. On the current engine, i started it twice for about 5 minutes each time, then Dropped the engine to put the "new" head.
Tried running that, and it didn't start. Then realized all the exhaust valves had zero clearance. Took me about a week to get new shims and set the clearances, and now, I'm getting smoke in my crankcase + strong bursts of air coming from my oil fill cap on the clutch cover when trying to start.

My compression tester is about a month away, so I can't tell how bad the compression it till it arrives, but I'm dead sure I'm leaking a lot into the case.

 

Took the head and the jugs off. As I suspected. Fully Bound rings on 2 pistons, and partly bound in 1. See attached pictures. The only thing I can think of is not using enough oil during assembly, but the engine ran after assembly, so...

 

i don't know all the details of you build so its hard to say but you don't need to oil the rings when you install them that shouldn't cause them to seize. i would guess its something along the lines of incorrect rings, improperly fitted rings like the end gap is off and maybe causing them to bind, or something from the nicosil coating isn't right and maybe clogging up the ring grooves? its not letting me open your pics right now but i will look again later. are they oem pistons and stock bore or are they oversized?? oem rings? when you built the motor did you check the end gap clearance? have the barrels been rebore or honed, replated anything along those lines? why are you replacing the head? what else was done in the motor build? maybe some more pics of the head and barrel mating surfaces and the bore's of the cylinders. this has me really curious whats causing this.

 

So, everything about the cylinders, pistons, and jugs are stock and unadjusted. I replaced the rods and crankshaft cos of spun bearings. I didn't take out the pistons when replacing the rods, so I didn't get to measure the end gaps on the rings.

Now that I think of it, the knock was caused by oil/water contamination at the oil cooler (wrong ring seal installed).. It could be that water had gotten to the piston rings and caused rust and the binding. Luckily I was able to pull out the rings, and there's some brown discoloration on them.

 

yea that would do it. when you said build i assumed you mean more parts were changed but yea stock pistons and rings shouldn't be having that issue and oil contamination would definitely do that. i would install new rings and clean the pistons well. have a machine shop give the barrels hone to put the crosshatch back in and the rings will seat right in like new. were you having an issue with the old head?

 

The old head was fine. I only took it off to test the new head that I put in. Some shop had condemned this new head as "leaking" (their words, not mine) and made the original owner buy a new head. Had to fix his engine anyways, and found a bent and a broken oil ring on 2 pistons, so I figured the scrapped head might still be good. Clearances on the head were also out, so I fixed that. New head gasket also, so I'm pretty confident in the head now.

 

Another possible source of g contamination is make up ok the piston heads.

One set of rings that didn't bind and still looked shiny had some grime in it too. @bacchus40 when cleaning your a surfaces before installing your gasket, be careful not to dust anything down your juggs.