Cylinder repair possible?

[woodworkingboy]

I thought Al would be a good person to ask about this, but since piston/cylinder damage is something that a lot of chainsaw users encounter, figured that it might be useful to start a thread on the subject.

I have a Husky 359 that I modded extensively four or five years ago, and it has been my main felling saw for smaller to mid sized trees. It suddenly lost compression last week, and thinking that the sealant that I replaced the cylinder gasket with probably blew out, I pulled it apart. It turned out to be a more serious problem. It appears that one of the piston retaining clips broke apart where the curl at the end is, then it must have fallen into the crank case and then was shot up through an upper transfer, where a ring hooked it or the piston edge. It chipped off a small edge from the piston crown, which I think is repairable with some careful welding and filing the ring groove. I have successfully tig welded on a piston before. The ring broke but stayed in it's groove. It is a pop up piston so there isn't a lot of width between the groove and edge of the piston crown. I would prefer to use the piston if repairable, given the work that has gone into it. The main concern is that the retaining clip piece appears to have been dragged up the side of the cylinder wall, so that there is about a 1/32" wide groove in the wall from the top of the transfer to the edge of the flat area around the edge of the combustion chamber. The small broken clip piece was imbedded in the top of the cylinder, and it pried out. There is no other damage, pretty lucky, I think. It would probably run reasonably decent still, but will loose compression down the groove, bypassing the ring. I'd like to be able to patch it, it is a narrow slot.

I have heard of people using some adhesive filler type material to reshape a cylinder wall, but have no experience doing it myself, and don't know what might work. It has to be a very hostile environment for a filler on a cylinder wall. I figure that if I can find something that might work, I can over fill the slot and then sand it down flat. Any suggestion what might possibly work to patch a scar on the inside of a cylinder?

Thanks for any thoughts.

 

[pigwot]

I don't know of an adhesive which holds up to the severe conditions. Fill the groove with a thin bead of weld and rebore the cylinder? Oversize the bore and a new piston and ring?

 

[woodworkingboy]

That would really be a chore to weld on the upper part of the inside of the cylinder, very tricky and I am skeptical of the results. I can see easily messing up the edge of the combustion chamber, and it is murder to get in there to file. I wonder what welding would do to the hard chromed coating they have on the surface, or whatever that is? I remember Timberwolf talking about building up a cylinder wall with something besides weld, some metal filler product, I believe.

 

[woodworkingboy]

I see some folks on the web, shouting the praises of J-B Weld for cylinder repair. I have never used it myself.

What one fellow had to say during a discussion about a groove in a cylinder wall, it seems simple enough if it works:

"I've successfully fixed this same situation with J-B Weld. My twist on it is to wait until it starts to firm up just a bit, oil one of the piston rings (so it won't stick to the epoxy), insert it squarely in the bore and push it all te way through into the crankcase. Voila! An instant smooth, perfectly level and round bore surface!

The abrasive stuff in J-B Weld is powdered steel. Shouldn't cause a ring wear problem IF the surface is level. It's very difficult to get a level surface by other means, but this is a snap!"

I think this discussion quote above is specific to the lower part of a cylinder, which is subject to less heat compared to up around where the combustion takes place, as in my situation.

 

[Tucker943]

I just can't see it lasting Jay.

 

[woodworkingboy]

My thought too, Chris, probably will melt out.

 

[SkwerI]

I don't think it will last either, but if I were going to attempt the J-B thing I would insert the ring in the cylinder first. Then fill the putty in the groove and pull the ring out when it's ready. Otherwise you would end up pushing the excess up into the top of the cylinder where you can't clean it out easily.

 

[sawinredneck]

Devcon makes some great epoxies we used on aluminum molds that worked great! Might check their website to see what products they might have? But I can't say I'm optimistic about it!

 

[sawinredneck]

Just checked, they list temps at 350 and lower, it's not looking good there.
http://www.devcon.com/products/products.cfm?brand=Devcon&cat=Metal Repair

 

[woodworkingboy]

Thanks for the input. There are lots of different solders, some higher melting temps than others. I don't think it would be too hard to run a bead down the groove, then sand it flat with some emery cloth. The question is whether it could take the heat of combustion without going soft.

 

[sawinredneck]

Seems the max temp will be around 2500 deg, near as google can tell me at least?

 

[woodworkingboy]

Thanks Andy, any idea what the combustion temp is in a cylinder?

 

[sawinredneck]

That seems to be the max temp gasoline can flame at, 2500 deg, add the cooling effect of fresh gas, the cooling properties of the materials and their thermal transference, ambiant air temp and humidity, sure?

 

[Al Smith]

If it goes above the bottom of the exhaust port it's not a good option to use epoxy .Below it might work to some degree .Providing it isn't in the ring travel .

You can't just bore out a cylinder on a modern saw because they have a plated liner and you can't run aluminum on aluminum .Even if you did bore and replate the cylinder unless you special order a custom piston they aren't made in over size .

The way I repaired one of the Mac 125 's was boring it 70 thou over and pressing in a grade 50 gray cast iron sleeve .It was a McCulloch though and had a thick enough cylinder wall to be able to be bored .

About the only way I can possibley think to do a modern cylinder is to only bore it 20-25 over and press in an undersized ID sleeze then finish bore it to size with the sleeve in place because with only maybe 10-12 thou wall thickness you'd certainly either warp or break the sleeve should you try to press in a thin sleeve .

Rather than cast iron type 4140 steel might get the job done because it's the material they use for aircraft engines.However it doesn't transfer heat like cast iron nor does it finish out as nicely as cast .Much harder to machine .

 

[woodworkingboy]

Thanks Andy. I like the idea of trying solder, if I can find some high temp hard stuff, and a gun that will melt it.

Al, the narrow slit is from an upper transfer all the way to the top. In the main heat zone, I guess you could say. I have a lot of work in this cylinder, I'd sure like to use it.

 

[sawinredneck]

Maybe talk to a coating company and have it replated? I was going to have some spindles crea-coated then turn them down but that deal went South. But you could have it nikasiled then hone or bore it down to size?
Just some food for thought.

 

[Al Smith]

Oh Jay I hate to tell you this but you're talking a couple hundred bucks state side to get a cylinder replated .Now maybe in Japan it might be cheaper but I'm afraid the cylinder as much work as you've done to it is toast for all practicle purposes .Chit happens ,I can attest to that as factual .

Best shot is find a doner and rebuild it .If you can do it once you can certainly do it again .Might be better anyway .

I mean you could buff it out as best you can and run heavy oil mix but as deep as the groove is it will never run right .

Normally a low spot won't hurt you .A high spot will break the surface tension of the oil film .One that wide usually won't work out .

 

[CurSedVoyce]

P&C kits for that saw are around 80-90 dollars. You might want to consider a redo Jay.

 

[Al Smith]

More .Since the thing is pretty well shot ,put another circlip in it it,buff it out as best you can and fire it up .The SOB will either run or blow like a bomb .

FWIW the Rocky special 038 Mag I got from B is not perfect by a long shot .Piston is grooved but the pot licker will run neck and neck with an Ms 660 in large wood running a 7 tooth .Now how long it will run I have no idea but if it's already on it's last legs run that dog until it blows .

It might surprise you how long they can run dying on the vine .

 

[woodworkingboy]

Thanks guys, I'm slowly getting resigned to the fact that the cylinder will now best serve as a conversation piece. I'd still put it together and see how it runs. it wasn't starting a all, but that was with the broken ring. I haven't completely given up hope of filling the grove somehow, but nothing so far is looking promising. Ah well, I can't exactly remember, but I think I might have used the existing circlip when i did the mod, instead of replacing with a new one as recommended. A good lesson, perhaps.