Chain saw overhaul - a few tech ?'s

[davefr]

I picked up a Husky 41 for next to nothing at a garage sale. The owner was selling it as a parts saw. It looks absolutely brand new so I decided to try and fix it.

The cylinder, piston, and piston ring have scoring on the exhaust side. What typically cause's scoring???

I removed the piston ring and it looks slightly narrower in the middle than at the ends. Is that from wear or are they produced that way?

I polished most of the scoring off the piston and cylinder wall starting with 240 grid silicon carbide paper and ending at 600 grit. There are only 3 very slight vertical lines but it's way better than it was and you can't even feel the scoring anymore. Should I polish finer than 600 grit or should the cylinder have a courser than 600 grit pattern?? I want to avoid removing too much material.

I plan to buy a new piston ring. Would it be wise to remove the piston from the rod and rotate it 180 degrees to equalize the wear??

There's a cap that bolts to the underside of the cylinder. Should I use gasket sealant. Is there any pressure or vacuum on the underside of the cylinder?

I know the proper repair would be to replace the cylinder and piston assembly but I'm not going to spend $150 on a saw that I'm into for $5. Are there any other suggestions for my budget overhaul?

Thanks

 

[sonny]

With the scoring on the exaust side, tells me it ran to hot. A number of reasons, 1st I would say fuel mixture.2nd carb adjusted to lean.Before you fix figure out what caused the problem.You can not rotate the piston.I dont know what to tell you. Sounds like you bought a parts saw.If you dont want to spend the extra $100 or so .& my oppinion is go for the new cyl. & piston.( Its just my oppinion).My question is a single ring?Im not real familar with the huskys.

 

[treeclimber165]

Yup, some idiot put 2-cycle oil in the bar oil tank and thought it would mix itself. Straight gas will ruin a new saw in less than 1 tank. Sounds like you need a new piston.

 

[HUSKYMAN]

I would get a new ring and throw her back together. You have nothing to lose. I have seen saws with light scoring run for years, but like sonny said there is another problem that caused the damage in the first place. Put good mix in it and reset the carb settings to stock if they are screwed up.

 

[sonny]

Your talking (Stihl orange). right husky man

 

[HUSKYMAN]

Sorry, only solid orange, no white allowed. Though I did test my buddies 046 magnum yesterday and it was pretty impressive. Not enough to convert me, though. It was too quiet

 

[Chain Gang]

Hi DaveFR,

Yes, the underside of the cylinder MUST be completely sealed. Otherwise, you will have a very lean fuel/air mixture and more overheating. Be sure to use all new gaskets on clean surfaces when you put it together. You may be able to get someone to vacuum test your engine for leaks once you get it assembled.

The real question about how well your rebuild will work depends on what lines the inside of your cylinder. A scratched cylinder can run for years if the cylinder is lined with cast iron or nikasil aluminium. If it is chromium plated on aluminium and the scratch goes most or all the way through the plating, the cylinder will not last very long at all. The 600 grit paper you chose should be fine.

Try to polish any big scratches in the piston and make certain the ring grooves are completely clean before installing the new rings. Because you are trying to make a difficult situation work, I would probably put extra oil in the first tank of gas. Run the saw with the chain installed at part throttle for 10 minutes or so without cutting any wood to give all the parts a chance to break-in without the extra heat of cutting wood.

Good Luck!

Carroll

 

[davefr]

Thanks for all the replies. This is great info!!

I sure didn't detect any oil in the residual fuel. There was no oily-ness whatsoever but it might be pretty hard to detect at a 50:1 ratio. The carb jets were about 3/4 turns out. (shouldn't the initial settings be 1 full turn turn out?)

All else looked great and the cylinder and piston polished up real nice. Does anyone know if the cylinder on these consumer Husky's is chrome plated or an alloy? It sure doesn't look like plating to me.

Fortunately Husky still sells individual piston rings for this saw. (The cylinder and piston priced out at over $100 which wouldn't be worth it.)

Thanks again

 

[HUSKYMAN]

I am sure it is lined with at least chrome, it has been some time since there was a saw made of just cast iron. The plating will be extremely thin. It will not look like a sleeve. You should be able to tell if there is oil in the gas, it should be green or black depending on the oil.