Overheated husqvarna 555, what to do?

chainsaw dummy · Feb 7, 2023

I scored (heh, pun) a couple non-op saws at a garage sale and fixed them up. With a new spark plug and cleaned carb the husqvarna 555 ran fine, except it wouldn't low idle. It could high-idle for minutes on end, and throttle up fine and cut, but then died shortly after letting the throttle off.

I am new to fixing chainsaws, and I found people saying you can reset the autotune to fix the idle by doing a 3-minute cut keeping the saw in wood the whole time.. and I didn't think about the fact that that could overheat the saw - I normally wouldn't do such a prolonged cut at full throttle. I'm kinda new to chainsaws, and I was an idiot. I set a timer and started ripping an old log from end to end, and after two minutes the saw shut off and won't start, and has very little compression (cord pulls too easy). You can laugh I know this was dumb.

The saw was in good shape before this it seemed, hadn't been used much, had the original bar and chain with not too much wear. So I think the only things that need replacing are whatever I damaged by overheating it. Presumably the piston, maybe the cylinder too.

1. Besides P/C, What other parts I should look at? Anything I should replace at the same time regardless, knowing that I overheated the saw?

2. How can I tell if the cylinder needs replacing as well as the piston? Or should I assume both do?

3. I see an oem P/C kit for this saw is $200. Ebay has cheap ones for $68 presumably from china, anyone use those? What's the best option? I do want to use the saw, and I'd rather be frugal if there's a cheaper way to get a piston and cylinder that will be good enough.

river of smoak · Feb 7, 2023

I was in a similar situation last winter when i got my 555 . It took awhile to fab up some block off plates to pressure test it , but I felt it was worth the effort to know the seals and gaskets were not leaking . next , the cylinder came off and the aluminum transfer was able to be cleaned off and the cylinder was saved . The piston was toast , so I got a meteor with cabers and put the saw back together . The saw hardly ran . Took the carb back out and put a kit in it and after some sketchy moments of running it seemed to clear up and run great . Ran about ten tanks thru it in 10-18 inch red oak with a smile .

chainsaw dummy · Feb 7, 2023

river of smoak said:
I was in a similar situation last winter when i got my 555 . It took awhile to fab up some block off plates to pressure test it , but I felt it was worth the effort to know the seals and gaskets were not leaking . next , the cylinder came off and the aluminum transfer was able to be cleaned off and the cylinder was saved . The piston was toast , so I got a meteor with cabers and put the saw back together . The saw hardly ran . Took the carb back out and put a kit in it and after some sketchy moments of running it seemed to clear up and run great . Ran about ten tanks thru it in 10-18 inch red oak with a smile .

Thanks river of smoak.

So if I'm lucky like you, I could get one of these meteor pistons for $45 and that might be all I need for parts.

When I get it apart I'll post some photos of the inside of the cylinder here and see if I get any opinions on whether the cylinder needs replacing too.

huskihl · Feb 8, 2023

You need to vacuum and pressure test to see if it has an air leak. It’s either sucking air or has an obstruction in the fuel or impulse circuit

Okie · Feb 9, 2023

After working on a chainsaw I have a big log right outside the shop and to confirm that a chainsaw is not overheating I use a 3M IR thermometer (one that is reliable) and monitor the block temp while in a full bar cut with a sharp chain so as to load up the engine good.

You can play with the IR temp using other saws first so as to get an idea of what to expect then go to your 555.

If I see a block heading toward 350F fast (less than a minute run) or getting in the vicinity of 350F I take it out of the cut and let the engine run out of the cut while monitoring the temp and most generally it will immediately start cooling down. If you kill the engine the temp will sometimes keep rising for awhile.

Using the IR temp will keep from ruining a new piston/jug from overheating.
Usually it's the piston swelling into the cylinder when overheating starts and can happen very fast on a chainsaw. (and most generally it's caused from the engine running lean)
lean means: lean on gas or too much air
You can search on-line for some tips about such and also this site.

If the saw's operator is not familiar with such when overheating first starts he usually thinks the saw is just bogging and lifts it out of the cut until it rev's up again then back into the cut and it starts bogging again USUALLY because the piston is swelling and scuffing the cylinder wall, eating itself and this can happen very fast to the point that the engine will stall and actually lock up then may crank over and sometimes start after a cool down.

irhunter · Feb 9, 2023

chainsaw dummy said:
I set a timer and started ripping an old log from end to end, and after two minutes the saw shut off and won't start, and has very little compression (cord pulls too easy). You can laugh I know this was dumb.

For the record, the 555 is a semi-pro saw which is designed to run WOT in wood for prolonged periods of time. Your 2 minute cut did not melt the piston. Probably an air leak, maybe a carb out of adjustment. Not 2 minutes in wood.