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Stuck Rings



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Bitter

Hey, i have a piston with some stuck rings and I'm wondering what i can do to get them unstuck. i've tried some mechanical methods, picks, tapping with a hammer, rolling against a cast iron table while tapping with a hammer. nothing! so now I'm soaking it in ATF, i let it sit overnight in the cold (freezing up here now) and then i microwaved it for 3 minutes till it was very hot and its still soaking. if this doesn't work, what else should i try?

when i was searching i found some WEIRD home remedies for rust, such as a dilution of water and molasses to remove rust. i may try it on the crankshaft of this engine since theres some hard to reach areas of it.

if you're wondering, the engine is a 1977/78 Minarelli V1. the stuck rings and rusty crank are the parts engine which I've split and setup for testing

https://img.photobucket.com/albums/v335/huz...ed/PICT0025.jpg

https://img.photobucket.com/albums/v335/huz...ed/PICT0031.jpg

I'd like to try to save this piston since its in good shape. I've been working the cylinders lip down to raise compression, and with this mock up and a few more bolts and nuts and a aluminum head gasket i can check cold compression off the engine to see how much I've raised the compression.

Hmm - for really stuck on rings, I usually try and heat up the piston with a torch and hit just the rings with a stream of water from a spray bottle. The steam produced basically blows the carbon right out of there. But if the carbon is really thick and there is corrosion as well - you can try some steel fishing leader - the braiding, flexibility, and thiness of the line help you cut right into the carbon and give solvents a chance to break it up. I've used this latter method with great success when coupled with engine degreasers. You have to watch it though - most degreases are very basic in pH and will eat an aluminum piston and its alloys.

Bitter

ok, after soaking in ATF for about 24 hours then i heated the piston to very hot and blasted the ring gap with compressed air as suggested by a 2 stroke forum, but that didnt work. ive heated it and dunked it in cold water and cold solvent as well. i'll try dripping water into the gap with it hot and see if the steam can loosen them.

any other suggestions?

Might try and find a dental pick to help dig up some of those deposits. The ATF and other solvents just have a tough time getting through. If you give them a little help by digging around the rings (hard to tell - but it looks like there isn't a whole lot of room there - looks pretty tight). I assume you tried all the penetrating stuff - PB Blaster, WD-40, etc.

Might try an old school mix - equal parts of kerosene or diesel and ATF (some say equal parts of kerosene, ATF, and WD-40 - never tried myself though). Pretty thin stuff, can seep in the tight cracks. I did that with an old big block that sat for 15 years - just filled up through the sparkplug holes and let it sit a few days.

Another method is called the skateboard wheel technique - basically keeps beating the stuck ring with a rubber wheel with a slight eccentricity on a drill press or similar - basically vibrating the pentrating solvent in there.

Tough part - is that is very hard to chemically dissolve carbon deposits - if you can do it easily - most polymer chemists would be very interested (think dissolving carbon nanotubes - pretty tough unless you use a certain organic solvent - even then it has a hard time dissolving it).

Bitter

i dont see any deposits really, and the gaps around the rings are TINY. this is a 50CC piston (1st pic), theres just not any room to get anything in there really. ive tried picking at the endgap, but theres an alignment pin in the way!

the ATF boiled from behind the rings, so it got all the way around it. im not sure whats keeping them in there. i'd hate to junk this piston just becase i cant de-ring it. a new piston is like $60.

Yeah - that alignment pin can be a pain - usually the ring is open enough to shove in a ring expander (the little ones are called thumb savers) and pry the ring off. But that only works if the ring moves around on the piston. If you can get solvent to move around the ring and there doesn't seem to be any deposits - you might have to just pry the ring off and risk breaking it - cheaper than a piston and most of hte time, have to replace them anyway.

Might just need some more soaking - ATF works great, but if you can soak it at a higher temp (nothing crazy, just a little higher than ambient) would help it a great deal. Might be able to find a parts washer cheap that will circulate and heat solvents safely (I picked one up at TIP a long time ago - ran me $50 for a 12gal unit - cleans just about anything given enough time).

Bitter

well i got my GF a 3.5 gal for about $20, i think the 12 gal cost a tiny bit more now a days default_tongue $20 was 1/2 off with my discount on a very basic one. metal tank, pump, spout, shelf, lid, and it even came with a switch AND a hinge!

i had the ATF at about 175 when i was soaking it.

NILLINOIS

well i got my GF a 3.5 gal for about $20, i think the 12 gal cost a tiny bit more now a days default_tongue $20 was 1/2 off with my discount on a very basic one. metal tank, pump, spout, shelf, lid, and it even came with a switch AND a hinge!

i had the ATF at about 175 when i was soaking it.

Have you tried PB Blaster? That stuff will get the most siezed bolts out. Don't know about the rings.

Bitter

i got em out. i found a screwdriver small enough to get between the endgap and the pin, then i pried up a little and a peice a ring came out. they ended up coming out about 1/4 inch at a time, some places were already cracked and others i did the breaking.

Bikeman982

i got em out. i found a screwdriver small enough to get between the endgap and the pin, then i pried up a little and a peice a ring came out. they ended up coming out about 1/4 inch at a time, some places were already cracked and others i did the breaking.

The rings were shot and breaking them was probably the only way you could have removed them.

Bitter

since i'm just a showoff, i got my newer piston, rings, and cylinder the other day. heres what i did with the piston with a couple spare minutes default_wink

https://img.photobucket.com/albums/v335/huz...ed/PICT0032.jpg

https://img.photobucket.com/albums/v335/huz...ed/PICT0033.jpg

https://img.photobucket.com/albums/v335/huz...ed/PICT0034.jpg

i'll run the wrist pin past the buffing wheel too to make sure its nice and smooth and i'll be polishing the heck out of the head too so its a nice mirror shine like the top of the piston. all of that should be a little more resistant to carbon buildup than the grooved machined surface and the cast face of the head, even tho its a surprisingly smooth casting.

default_biggrin Look at that shine!!

What's this engine from - scooter, moped?

Bitter

moped, 50CC minarelli V1 on a cimatti citybike. vintage from about 1977, its turning 30 yrs old this year and its about time it got some attention. this topend rebuild is just to hold over till the 75CC kit in the spring, with the right tuning i can crank 3.5-4hp out of those 75CC's and get the single speed motor going along at 40-45mph. enough to keep her up with traffic on most streets around here and to get her to and from school and work in the summer quickly.

Bikeman982

since i'm just a showoff, i got my newer piston, rings, and cylinder the other day. heres what i did with the piston with a couple spare minutes default_wink

https://img.photobucket.com/albums/v335/huz...ed/PICT0032.jpg

https://img.photobucket.com/albums/v335/huz...ed/PICT0033.jpg

https://img.photobucket.com/albums/v335/huz...ed/PICT0034.jpg

i'll run the wrist pin past the buffing wheel too to make sure its nice and smooth and i'll be polishing the heck out of the head too so its a nice mirror shine like the top of the piston. all of that should be a little more resistant to carbon buildup than the grooved machined surface and the cast face of the head, even tho its a surprisingly smooth casting.

Looks good. Nice clean shine and smooth, too. The critical dimension is the outside diameter and the fit in the heads. Should work very well if the tolerance is not too lose, or too tight.

Bitter

it works great, the single speed ped is hitting 30mph on a flat now, it was stuck at 25-27 before. compression is upto 115psi hot AND cold which means the rings are sealing perfectly!

heres the old piston, ick! i dont know how i got 105PSI compression with it and the thin rings.

https://img.photobucket.com/albums/v335/huz...ed/PICT0035.jpg the bore is pretty gouged up too, but nothing a couple hours of honing wont fix! but by then i'd need an overbore piston and ring set, not worth it. i'll just shave some off the good jug to raise her compression to fatten the powerband up a bit and give it a little more kick till more goodies come around default_wink

Bitter

i just thought i'd give an update.

i upped the compression from around 110 to around 140psi, tossed in some 92 octane and man does it take off now! she can put her feet up on the rest as she twists the throttle and off she goes. i think i cut the 0-30 distance by about 1/2 to 1/3! i bored the intake elbow and carb both to 14.2mm (9/16th drill bit is cheaper than a 14mm one), trimmed the gasket and ordered a scattering of jets. the carb and intake are on, but with the stock pipe its at 30mph still, tho its getting there alot sooner.

soon i'll be fitting an expansion chambered exhaust onto it, tuned for mid and higher rpm and for more flow, with the 14mm intake i should be able to crack past 30, maybe hit 35 or faster. this will hold over till the 75cc kit which will be able to propel to 35 pretty easily and possibly past 40mph with the right intake and jetting.

K_Watson

Can you post a pic of the actual moped?

Bitter

i havent tried, but both wheels would need to come off i'm sure. it barely fits in her (its my GF's moped) 93 escort wagon.

Bikeman982

How many MPG can it get?

Bitter

about 100 miles a tank, tank is less than a gallon. i'd bet its somewhere around 150 at the moment. that'll be changing for the better however, better being faster. a pipe will be fitted soon allowing it to break the 30mph which the stock pipe limits it to, 35 to 40mph on the flat should be attainable without a change in displacement default_smile

it needs new rings, as much material as i removed it should have higher compression than it does. i'm going to hone the cylinder to break the glaze again and then measure for new rings.

in the summer or spring a 75cc kit and bigger carb may be going on, then it will be able to spin the speedo needle past 40 and hold it around against the wrong side of the stop.

Bikeman982

about 100 miles a tank, tank is less than a gallon. i'd bet its somewhere around 150 at the moment. that'll be changing for the better however, better being faster. a pipe will be fitted soon allowing it to break the 30mph which the stock pipe limits it to, 35 to 40mph on the flat should be attainable without a change in displacement default_smile

it needs new rings, as much material as i removed it should have higher compression than it does. i'm going to hone the cylinder to break the glaze again and then measure for new rings.

in the summer or spring a 75cc kit and bigger carb may be going on, then it will be able to spin the speedo needle past 40 and hold it around against the wrong side of the stop.

If you go too fast on it, you may have to add wings!!

Bitter

just maybe default_wink theres a nice vid on youtube of a single speed Puch Maxi with basically the same mods i'm planning (but 64CC instead of my planned 75CC) pegging its speedo past 40, probably nearer to 50mph!

 

Bikeman982

Be sure to wear proper safety protection when riding - helmet, gloves, long sleeved shirt, pants, boots, etc.

We don't want to have stories about road rash and broken body parts, if you have an accident at 51.2 MPH.