Husky 181XP Compression loss between stop and (attempted) start.

[CheeseEater]

This saw had so much compression, it was very difficult to pull when cold. I've always mixed fresh gas 40:1 - no ethanol - and always cooled the engine after running with a 1-minute idle. Nevertheless, after shut-down following a job, I found the saw to have little compression. Spark plug was in tight. No decompression valve. Pulled it apart: the piston and ring looked good. But it appeared the ring may have bound up to the piston. I removed it, cleaned it and reinstalled as it was - the correct way, and it moved freely. No change. So I assume I need to rebuild.
Question: mid-point on the wrist pin, at the connecting rod, there's a hole on each side, and I assume this is solely for lubrication. I can get the pin to move but only to the edge of the piston; it won't come out any further, and with my old eyes I'm wondering if there's damaged metal preventing removal. The retaining clips looked good.
Also, there's an electronic box 501812702 that appears to be missing, that should be between the stop/start switch and the ignition coil. It's almost $90!! Yikes. Are there any cheaper alternatives I can use/try?
It's a great saw that I'd hate to spend a lot of money on. But I don't want it to be a boat anchor, either. Thanks in advance for your ideas.

 

[Marshy]

When you put the wrist pin clips in they can sometimes throw a little burr on the hole of the piston. You can take a razor blade and deburr the hole and see if the pin slides out (dont go crazy, just break the sharp edge of the hole). Otherwise you might need to press the pin through. It might just be residue buildup on the pin surface. You might be over thinking it regarding the ignition box. Change one thing at a time. Did you do a compression check? Its hard to believe you would have compression just drop like that without some indication on the piston or cylinder. If the flywheel slipped on the crank or anything else happened to ignition it would affect performance but not compression. Got pictures?

 

[CheeseEater]

Sorry, no pictures; it's all put back together. I threw in the other questions just because I was on site. Actually, there is better compression now, but not what it was. Tried for a few minutes to start it and gave up, for now.

 

[old-cat]

Maybe the ring is worn out? What's the end gap?

 

[PES+]

You most likely need to open it back up and get some pics.

Worn out ring at least that may have finally lost all tension and collapsed into the piston ring groove on cooling.

The electectronic box is there unless you removed it is under the recoil gapped to the flywheel like a one piece or ponts igntion

It is the trigger and primary coil of the ignition as the saw would have no spark nor run without it.

 

[CheeseEater]

Maybe the ring is worn out? What's the end gap?

I'm such a neophyte, I don't even know what that is or how I'd measure it.

 

[Marshy]

I'm such a neophyte, I don't even know what that is or how I'd measure it.

To measure the ring end gap you have to take the cylinder off, take the ring off the piston, put the ring in the cylinder bore, slide the piston into the cylinder to drive the ring in a little further into the bore (the crown of the piston will square up the ring to the bore), then use feeler gauge to measure the end gap in the ring.

 

[old-cat]

I'm such a neophyte, I don't even know what that is or how I'd measure it.

Exactly as Marshy said.
I'm the guy you called from the craigslist ad. Call me again, anytime.

 

[RedneckChainsawRepair]

No way I would have reused the ring after sticking it like that. $5 ring is so much cheaper then my time doing it again.

 

[CheeseEater]

No way I would have reused the ring after sticking it like that. $5 ring is so much cheaper then my time doing it again.

Not a mechanic, here. Just thought I'd give it a shot looking for something obvious. The guy who gave me the saw said he thought it had been rebuilt then set aside for a number of years. Don't even know where I'd get a ring for this old saw. But I'll look around.

 

[RedneckChainsawRepair]

Not a mechanic, here. Just thought I'd give it a shot looking for something obvious. The guy who gave me the saw said he thought it had been rebuilt then set aside for a number of years. Don't even know where I'd get a ring for this old saw. But I'll look around.

You have the 1 - 1.5mm ring?

 

[CheeseEater]

I'll pull this apart again today. Seeing 52 and 54mm pistons/heads for sale on eBay, I'm not sure what I've got. My guess is 54mm.

 

[mdavlee]

181 should be 52mm. If it's a thin ring piston rings will be higher than a new piston.

 

[CheeseEater]

181 should be 52mm. If it's a thin ring piston rings will be higher than a new piston.

52mm with 1.5 ring, end gap .012-.013 (not sure where to find specs.) Photos coming (I hope).

 

[Marshy]

I'll pull this apart again today. Seeing 52 and 54mm pistons/heads for sale on eBay, I'm not sure what I've got. My guess is 54mm.

I don't know what's available (OEM or AM) but not all after market (AM) parts are created equal. Let us know what you are thinking about buying in case someone can save you another headache.

 

[Marshy]

52mm with 1.5 ring, end gap .012-.013 (not sure where to find specs.) Photos coming (I hope).

Sorry, I can offer much help on this. I know piston rings are generally x.xxx inches of end gap per inch of bore. You number seems a little hight to me off the cuff. I'd wait for someone else to chime in about your clearance. Do what it's worth you might be better off replacing it if a new OEM ring is available and cheap. I wouldn't hesitate to buy a new OEM ring for $20-30 if it were available.

 

[old-cat]

52mm with 1.5 ring, end gap .012-.013 (not sure where to find specs.) Photos coming (I hope).

I doubt that's where your problem is but it does need a new ring

 

[old-cat]

http://northwoodsaw.com/store/index.php?l=product_detail&p=212

 

[CheeseEater]

I'm such a neophyte, I don't even know what that is or how I'd measure it.

End Gap is .012-.013

 

[CheeseEater]

Photos attached: 52mm piston with 1.5mm ring with .012 - .013 end gap.