In the process of rebuilding a 1987 yamaha 150 2 stroke. During the summer i melted piston #3 i had that cylinder bored out and the other cylinders just lightly honed. The guy at the machine shop said i could reuse the piston rings in the other cylinders since i only have 500 hours on the engine. He said people do it all the time. What u guys think? I kept all the rings with each piston and marked each set as to which cylinder they came out of.
2-stroke yamaha re using piston rings
- Thread starter lime4x4
- Start date
Considering all the effort and expenses you are incurring to fix one cylinder, I would at least check the ring end gap to make sure you don't put an excessively worn ring back in. I'm not aware of a ring face having a special finish to aid with break-in, but someone like Wiseco could tell you.
Did you ever determine what fried that cylinder?
Did you ever determine what fried that cylinder?
Never did find a root cause of the failure. I will check the ring end-gaps. I know the original rings face area are all nice and shiney. 4 stroke engines i know this is my first rebuild of a 2 stroke. I'm looking at around 250 bucks to replace the rings in the other cylinders. I'd just hate to spend the money if i didn't have too. 250 bucks buys alot of bait and tackle..lol... I work at a chevy dealer. the newer engines when i'm replacing piston and rings your not allowed or suppose to hone the cylinders. U just remove the piston and rings and install the new components with a little oil
Since your original failure was most likely caused by a ring failure, why take a chance on the other rings?lime4x4 said:
Also make sure that the ring groves are completely clear of buildup. I would also research the issue of honing the other cyls to allow proper ring breakin. The cylinder sleeves in 87 were not manufactured like today's and I suspect that honing(lite) is desirable.
If the gaps are good, the pistons free of carbon in the grooves, and the machine shop is reputable with a lot of large displacement outboard experience to back up the suggestion, run it!
The only good way to inspect the grooves is to remove the rings. If they have become brittle that puts strain on them that could contribute to failure. For all the expense so far and the time and labor, I just don't see how reusing old rings is advisable. The rings are 26 years old!family affair said:
Seasick,
Respectfully, how does a ring become brittle? With steel cylinder liners all 2 stroke rings I have encountered are a high chrome alloy. They don't break easily. I've tried! If the rings got hot enough to affect the integrity of the material, I would think the piston and cylinder would show issues too. A ring can't move nearly enough in the groove to cause the material to fatigue. As for age, metals integrity don't change by age. Excessive heat, stress (form excessive carbon build up), and corrosion of course will. If a lot of carbon was present on the rings at the time of the tear down, I would also agree to replace them.
I agree, that ideally one replaces all wear components on a rebuild to help ensure the engine operates to its intended design life especially if the engine is regularly stressed to its design limits. I doubt lime is going to attempt to get 3k hours out of this engine or run it WOT constantly to get there.
Ignoring all of the above, if a reputable machine shop has significant experience with big outboard and this issue, I would have faith the man knows what he is talking about. Ruining his reputation for $250 is not worth it. However, if he is sketchy, order new rings asap! :mrgreen:
Respectfully, how does a ring become brittle? With steel cylinder liners all 2 stroke rings I have encountered are a high chrome alloy. They don't break easily. I've tried! If the rings got hot enough to affect the integrity of the material, I would think the piston and cylinder would show issues too. A ring can't move nearly enough in the groove to cause the material to fatigue. As for age, metals integrity don't change by age. Excessive heat, stress (form excessive carbon build up), and corrosion of course will. If a lot of carbon was present on the rings at the time of the tear down, I would also agree to replace them.
I agree, that ideally one replaces all wear components on a rebuild to help ensure the engine operates to its intended design life especially if the engine is regularly stressed to its design limits. I doubt lime is going to attempt to get 3k hours out of this engine or run it WOT constantly to get there.
Ignoring all of the above, if a reputable machine shop has significant experience with big outboard and this issue, I would have faith the man knows what he is talking about. Ruining his reputation for $250 is not worth it. However, if he is sketchy, order new rings asap! :mrgreen:
I removed the rings from the pistons. The grooves and top of the rings are carboned up which i assume lead to the failure i had. Cleaned the carbon off the rings and piston grooves. Check end gap and there all still within specs. After cleaning up the block i found two small cracks where the head bolts go. So i'm gonna roll the dice and reuse the rings. I don't run at full throttle often i do more drift fishing. I'm only looking to get another year or 2 out of these engines. Next year i'm gonna start looking for a set of newer 2 strokes or maybe a set of used 4 strokes
family affair said:
You could be right I guess. I wish Lime good luck with the rebuild. Nuf said about this topic
Lime, the cylinders are not all identical and the rings seat to the individual cylinders. I wouldn't consider using them again if they were mixed up from their original positions. A lip forms near the top of the cylinders from normal wear above where the ring tops out. If not taken out and a different ring hitting it, ring will break. But being the cylinders were honed, I would just spring for a new set. Nothing like regret after the fact. You seem comfortable doing as you are but no surprise advice will be on the conservative side. We want to see success for you.
When i took it apart i put each piston,rings and bearings in a bag and marked which cylinder it came from. After finding 2 cracks in the block don't want to really dump alot of money into the engine. The cracks in the block are at 2 outer cylinder head bolt holes. So my plan is to jb weld studs into those holes then drill and install a roll pin thru the block and stud. Another reason why i was considering to reuse the rings is i actually found a few used rings for sale on ebay along with used used connecting rod bolts which according to the manual your not suppose to reuse. I'm also lokking at the fact that both engines are 27 years old. With my luck the other engine will crap out this year..lol... Plus i'm planing to replace both engines in 2 years