Topic: Best Way to Get Stuck Rings Out?

[Dr. Frankenstein]

I'm working on a '72 JDM CB500 and finding all kinds of surprises, like a spark advance with the little nubs broken off, a stubborn, rusty front brake reservoir, surface rust everywhere on the bike itself, and now some stuck piston rings that just don't want to come out of two pistons. What's a good way to get old, stuck rings out of the lands? I've already broken the compression and scraper rings on one piston - they are Stuck! I've tried heat, Kroil, PB Blaster, picks...what else?  They're standard 56mm.

[BenelliSEI]

I’ve had good luck putting them in a pot of boiling water for several minutes. Seems to loosen off the goo and open up the gap enough to start moving them….

[Don R]

 I had a set of 836 turbo pistons like that, I tried all of what you said and a few more, I ended up using more heat. I didn't use the boiling water though, that might be worth a go.

[Dr. Frankenstein]

That makes sense; it works on stuck carb slides...

[BenelliSEI]

That makes sense; it works on stuck carb slides...

Yes…. That’s what made me try it!

[bryanj]

To be honest if they are that stuck the grooves will be damaged anyway and have you checked the bores for wear, if rings are that bad chances are bores are rusty and need reboring with oversize kits anyway, check out Cruzinimage for piston kits

[Sw1ssdude]

Try to dissolve the carbon, with chem-dip, or ultrasonic cleaning, or heat (try not to heat-treat the rings). Then try to wiggle them free. the rings are bigger than the piston, and will try to spring back into their original shape. so help them work themselves free by picking them with something soft, like brass or plastic...

[dave500]

you can use SL or XL 125 pistons in the 500s,they are domed though so watch compression and head and valve interference,I used them in a 500 motor years ago.

[Dr. Frankenstein]

Bryan - the bores are fine, no marks or anything; I've already honed them and they smooth throughout. Cruzinimage does have a nice CB500 piston kit, but tariffs will probably double the cost. (Are tariffs hitting you guys over there as hard as they are here...?)

Dave - like you said, wouldn't the stroke and raised dome on those pistons interfere with the spark plugs and/or valves?

[Rayzerman]

Could be a little carbon build-up holding them.... you can soak in Simple Green Purple (good for all metals), or preferably in ultrasonic cleaner, 50% Simple Green/water, squirt of Dawn dish soap.  Most ultrasonic cleaners will heat up to 175F, so go for it.

[Dr. Frankenstein]

Yeah, I have a nice 30 liter Vevor with heating capability; I'll try boiling them and see what happens.

[MauiK3]

Watch the Simple Green, it can damage the soft metal, the 50/50 mix with water lessens the risk, otherwise it works well.

[bryanj]

Probably got some nos standard pistons about, not sure about rings though, postage is worse than tarriffs, had a christmas parcel from a mate in Nashville and wasnt charged, here it depends on value and if its comercial you pay VAT ar 20%

[HondaMan]

Bryan - the bores are fine, no marks or anything; I've already honed them and they smooth throughout. Cruzinimage does have a nice CB500 piston kit, but tariffs will probably double the cost. (Are tariffs hitting you guys over there as hard as they are here...?)

Dave - like you said, wouldn't the stroke and raised dome on those pistons interfere with the spark plugs and/or valves?

If you've honed them, there is already too much piston clearance. The result, if you use stock-size pistons again, will be lousy performance, oil burning and no idling.

If the 'nubs' are broken off the spark advancer, it probably means someone likely tried to use a Dyna S ignition on it (you must remove those pins to use its magnetic trigger on the advancer), then found out it used up all the power the alternator could makes- so the battery was always very low and the electric starter didn't work - and then the bike got parked.

I've seen this exact scenario more dozens of times than I can count, and was why I finally gave in and wrote the last book.

[Dr. Frankenstein]

HM - I didn't go nuts on them, just cleaned them up a little, probably 10 seconds at most, well lubed and moderate speed. I've done it before with no problems, i.e. my other 500, 550 and other bikes have had no problems. I didn't find an electronic ignition on it, I think somebody tried to turn the engine over with the big nut on the end of the points bolt and snapped 'em off. For the record, it wasn't me - I've made that mistake before!

Bryan - let me know if you have two CB500 pistons lying about you could part with (or anybody else, for that matter!) and what you'd take for them - although I may bite the bullet and try to get a whole new set, which would be optimum, but I don't know if that would be cost-prohibitive as yet...I think I have an extra set of new rings floating around somewhere from better days, but I'll have to go through all my stock to see.   

[HondaMan]

Is the 'nub' you mention on the crankshaft's end (that locates the spark advancer), not the one(s) on the spark advancer itself (under its points cam)?

[Dr. Frankenstein]

No, it's the ones on the spark advancer itself, not the one that plugs into the crank.

[dave500]

the valves clear the domed pistons fine,you might find them less expensive than 500 ones?

[Dr. Frankenstein]

What is that photo...? What is the stuff in the compression area?

[jgger]

Donut sprinkles? Maybe 😁

[dave500]

What is that photo...? What is the stuff in the compression area?

plasticene in the pistons valve pockets,showing how much clearance buy inserting a probe into it.

[bryanj]

I have 2 nos std Honda pistons but no rings.
You can have the for £10gbp the pair but postage will be £18gbp total £28.
Any charges at your end are down to you but i will mark as gift

Thats about $37 at todays rate