Good morning, I purchased a disassembled 500i that I picked up for a good price with the understanding that it needed a top end. My experience level only includes one top end on an 036 that had obvious P&C damage, which I replaced both, reassembled, and the saw still runs great. This saw does not have obvious damage to me, but I may not have the level of experience to see the problem. Piston rings move freely and I don’t see any scratches on the piston. Cylinder has some vertical shiny lines but no transfer or anything that I can feel. Any thoughts from those that have the experience would be appreciated.
Stihl 500i
- Thread starter 356marlin
- Start date
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I don't see any damage just normal wear
I'd clean the cylinder up and if the piston is not too worn I'd rering it or replace the piston and run it.
I'd clean the cylinder up and if the piston is not too worn I'd rering it or replace the piston and run it.
Yeah, I would say you lucked out.
Check the decomp valve and make sure the spark plug threads are intact.
Figure out why they thought it had lost compression.
Or, whatever their thinking was.
Check the decomp valve and make sure the spark plug threads are intact.
Figure out why they thought it had lost compression.
Or, whatever their thinking was.
Thanks for the reply
Dealers will say anything to get you to buy a new saw. Sounds like what happened to the previous owner
No expert here but I am a little concerned about the dark areas in the cylinder - almost like it was caught before it got worse. What do the rings look like? Are you planning on replacing them?
New in the box and only test fired at the factory looks the same way. The chrome lining is very shiny and any evidence of a piston riding on that lining is instantly noticeable
Would you think the rings should be replaced, just because I’m there? They look fine and spin freely. Not sure how to inspect them to know if there’s any wear.
Deglaze and new rings at least. I would get a piston while I was in there.
But the question remains, what really happened to the motor?
But the question remains, what really happened to the motor?
If they aren’t marked up, I see no need to replace them. I can’t imagine they are worn out yet. I would take a look at the crank and bearings though just to make sure they weren’t causing the low compression
Maybe I misread this - how would crank and bearings affect compression - extreme slop that reduces piston travel?
Yes.
river of smoak
ArboristSite Member
I think one way to inspect rings would be to take them off the piston and put them in the cylinder , square them up with the piston and check the end gap .there are published specs
Jza
ArboristSite Member
Funny enough I got a 500i same situation as yours . Was understanding it was low on compression .. Turns out leaking decomp , could hear it hissing . Plugged it , now it's got monstrous compression .
Definitely atleast get new rings and a gasket . if u want to try plug the decomp there only couple of $.
Definitely atleast get new rings and a gasket . if u want to try plug the decomp there only couple of $.
That makes sense - seeing as how a slight difference in the location of the schrader valve in the compression tester can make a big difference.
Yep I would think a 30–40 psi drop would be enough for a dealer to give it that designation. And if all the balls or rollers were on one side of the crank bearings, that would keep the piston from going all the way to the top
