Another ps5100 thread lol

[ktoom]

I purchased a used PS5100 on flea bay. The seller said it ran great. When i got the saw i removed the muffler only to see some scoring of the piston. Before i pulled the cylinder i checked the compression and it was at 190psi. I didn't release the air in the gauge so i could see if it would drop. It stayed right at 190 psi for over 20mins. When i pulled the cylinder off I got to see it better. I think i can get away with just cleaning up the piston/cylinder and just re-ring it. The piston has a small burr on the top and where the ring seats on the piston. Judging from my pic's, do you think it was the typical lean seizure?

 

[SawTroll]

It isn't seized when it runs well and has 190PSI compression, but it looks like it could be on its way to be.

Make sure that the carb isn't set too lean!

I find it a bit odd that the damage is just on one side of the exaust, but I am no expert on such damage. It is hard to imagine that any foreign debris could be present at the exaust side, unless the muffler has been off the saw.

 

[WetGunPowder]

Yep:agree2:

 

[ktoom]

I agree with you saw troll. When I seen the scoring I definitely wasn't going to fire it up. The muffler had never been off. From what I could see cuz the bolts that hold the plate on, in front of the muffler, had red loctite on them...... Unless dolmar doesn't use lock tight????? THe limiter caps were not trimmed, so I'm hoping that was the cause of the problem. There is some light scoring on the intake side of the piston, but on the left side of the piston. The scoring on the exhaust side is on the right side of the piston.

I got the piston cleaned up pretty good, so I just gotta get a ring and cleanup the cylinder.

 

[komatsuvarna]

I didn't release the air in the gauge so i could see if it would drop. It stayed right at 190 psi for over 20mins.

A compression tester can't be used for a leak down tester. There is a valve in the end of it that wont let the pressure go back to the cylinder.

 

[ktoom]

Duhhhhhh I knew that. I was just testing you guys. Time to bust out the mighty vac

 

[Little Al]

I purchased a used PS5100 on flea bay. The seller said it ran great. When i got the saw i removed the muffler only to see some scoring of the piston. Before i pulled the cylinder i checked the compression and it was at 190psi. I didn't release the air in the gauge so i could see if it would drop. It stayed right at 190 psi for over 20mins. When i pulled the cylinder off I got to see it better. I think i can get away with just cleaning up the piston/cylinder and just re-ring it. The piston has a small burr on the top and where the ring seats on the piston. Judging from my pic's, do you think it was the typical lean seizure?

Some years back whilst still road racing motor cycles, I had damage very similar to your photo`s to a Honda RS125 bike, the cause was part of the earth electrode breaking off the spark plug, bike still ran OK & finished the race only when stripping down for next meeting was it found, & yes it still had good compression

 

[PB]

I think Edge & Engine started a thread about piston wear on one side of the piston a couple of years ago. I don't remember the brand, but think it was either a Dolmar or a Husky. You might want to search through that thread (if you can find it) to see if there are any good thoughts on the subject.

If it were me, and I could get a piston at a decent price and the cylinder cleaned up, I would throw a new piston in there. That way you are never questioning in the back of your mind if it is going to go. A complete lean seizure of more scoring might ruin the cylinder completely and cost more money in the long run. Edge & Engine or Cuttinscott could get you a price on the piston. Just my .02.

 

[striperswaper]

why didn't you return the saw when you saw the piston?

 

[weimedog]

Looks like only aluminum wiped onto the barrel so that should clean up..I would get another piston and ring. They are cheap. Interesting place to see the partial seize. I would have expected it right in line with the exhaust. Wonder if this is a lean or at least running "hot" type of issue. I never worked on one of those Dolmars. But instinct would be to (After clean up & new piston/ring) to cut those limiters and add some fuel to the mix! Wonder what color your spark plug is? I some times wonder if they have an ignition timing issue? Even a cooling issue? Also wonder what fuel / oil ratio was used. Have seen so many threads relative to those little hot rods.

 

[ktoom]

why didn't you return the saw when you saw the piston?

I just got the saw yesterday. I don't think he knew of the problem. The muffler had never been off before. With that compression reading I got, the saw will run and work good... But like sawtroll said, who knows when it would actually blow. I bought this saw for half the price of my new 5100. I will contact the seller, but I'm not looking to start out a longgggg drawn out process with refunding everything. This saw might get ported while its apart so I will be happy either way.

 

[Chris J.]

Plus one for a new piston; that one looks highly questionable.

 

[cuttinscott]

new piston assembly is $67.26
ring is $11.98



Scott

 

[mountainlake]

That looks like scoring from not letting the saw warm up and running it hard. I doubt the seller had any idea what it looked like. Steve

 

[ktoom]

I agree, i honestly think that the seller had no clue only because i could tell the saw had never been apart since new. I sent him a message about the issue. After cleaning everything up, the ring and piston look good as well as the cylinder. Im just thinking of putting it back together and running it. What do you guys think? Anyone ever been in a situation like this where the piston and ring seem to be still good after cleaned up.

Another thing i just noticed was that the paint on the inside of the crank case, on the flywheel side, is worn off. Ive never seen it that happen before. The crank is tight and the con-rod is good too.

 

[striperswaper]

does it look like the paint flaked off? could that of caused the piston scuffing?

 

[grandpatractor]

Another thing i just noticed was that the paint on the inside of the crank case, on the flywheel side, is worn off. Ive never seen it that happen before. The crank is tight and the con-rod is good too.

That is the way they are. Looks worn off but it isn't.

 

[wse8562]

Looks like a saw not properly set by dealer. These saws tended to come lean from the factory to pass epa regs. Should have been richened up at set up. Also these saws tend to incease in rpm after intitial break in more than most. Put in the piston. Set it at around 14000 with a tach and you should be happy. The new 5105 addresses these issues plus has better cooling system too.

 

[Termite]

I would modify the carburetor diaphragm to vent to atmosphere instead of through the air filter!

 

[ktoom]

So the guy who I purchased the saw from, wrote me back. This is what he said
"this saw is used, runs perfect, i dont know what else to say, maybe you should have bought a new one! comp was perfect."

I don't know how to go about this cuz the saw did have good compression, but he never checked the condition of the piston or cylinder. If i hadn't pulled the muffler off, i would have never known of the problem either. I already have the saw apart and repaired it. I'm not trying to be a jerk to this guy, but i want him to know about the problem. I purchased a new ps5100s 2 weeks ago lol, so that's one response to what he had to say. But then again it has nothing to do with me buying a new. It comes back to him not checking his saw over properly before selling it and improperly describing it. I feel like i'm just gonna get into a pissing match with this guy and he's gonna think im a scammer and all that blah blah blah.