McCulloch Chain Saws

[Brian Thacker]

You will need to tare it down far enough to see the outside top of the cylinder. It will have a A, B or C stamped on it. You will match the piston up with that or if you have to have the cylinder replated then it won't matter they will fit the bore to the piston. By the way the A B or C is the size of the cylinder. It is very little but enough that it needs to be followed.

Brian

 

[Brian Thacker]

You saw has what is called Q porting. Looking into the exhaust port you see where the top of the port makes a upward peak. That is to let some compression off, enough to let it start easier. My self I prefer a compression release and have thought about putting one on my PM800. The Q port is in my opinion not enough to make an easy start.

Brian

 

[rwoods]

Rob, usually the cylinder is stamped near the spark plug hole. If there is no marking then consider it a "B".

Brian, have you seen a squared off Qport like Rob's. I don't think I have.

Ron

 

[Brian Thacker]

I have not seen a squared off port like that before. Wonder what that is all about?

Brian

 

[heimannm]

There should be a stamp on top of the cylinder indicating "A", "B", or "C". The "B" piston (92519) is readily available from cheapchainsawparts for $50, others come up from time to time typically from $69 to $99..."A" is 92518 and "C" is 92520.

There are no real tricks to disassembly of the 10 Series saws, just remember there are 8 screws holding the crankcase halves together, 4 internal (12-24 screws) and 4 external (8-32 screws). Remove the two screws that hold the clamp for the boot before you take the tank off the body of the saw, there is one screw in the oil tank that holds the front anti-vibe mount.

The 82 cc saws are thin ring except for a few early SP80 models, there are rings in there but they are stuck in the grooves.

Mark

 

[BigBlue]

Thanks guys. Went out tonight and pulled it pretty much all apart. Probably the only thing left is to clean it well and then pull the case halves apart. It was fairly straightforward except for: 1) getting the rear rubber isolators out from under the choke linkage and oiler linkage; 2) realizing that the carb-to-cylinder boot had screws under the carb; and 3) pulling the hose off that goes from carb area to crankcase. The latter wasn't actually hard, but I kept looking for a clip to release. Turns out it is just a wire ring crimped on or something.

Mine is a 'B' cylinder head, luckily, so that should be good for getting a piston, assuming the head is salvageable. Even found on on eBay for under $40. Not bad. Comes with rings and wrist pin (?) too. Does the "1186" engraved on the head mean it was made in 11/1986?

Thanks,
Rob

 

[BigBlue]

Will I have to pull the flywheel and clutch off in order to keep disassembling? The flywheel doesn't worry me too much but I thought I read that putting the clutch back on requires special tools?

Rob

 

[Brian Thacker]

No special tools to put on but may require a puller to get the clutch and flywheel off. Loosen the nut on each until the nut os level with the end of the shaft, pick it up by either clutch or flywheel which ever one that you are trying to get off and rapp the nut with a hammer and usually they will letgo. It is better to have them off. While rebuilding the saw you will want to replace the crank seals.

Brian

 

[rwoods]

Rob, should be wrist bearings with piston. Doubtful that a pin is included.

What does the cylinder look like inside? I am really curious about what appears to be a square top of the Qport.

Ron

 

[heimannm]

I'm guessing that is some aluminum residue off the piston making it look like that.

Rob - the clutch nut has a LH thread and no key so the clutch will come right off once you loosen the nut and give it a rap.

Mark

 

[BigBlue]

Rob, should be wrist bearings with piston. Doubtful that a pin is included.

What does the cylinder look like inside? I am really curious about what appears to be a square top of the Qport.

Ron

I think it was a 'piston pin' that is included. A small cylinder thing.

I haven't pulled the case apart today. Had to deal with other stuff instead. Maybe tomorrow. What does a 'normal' Qport look like?

Thanks,
Rob

 

[heimannm]

 

[BigBlue]

Yeah, that's what it looks like. Sorry if the other pictures weren't great. Here's another couple views.

 

[rwoods]

May just be the camera angle or some transfer or possibly a variance in casting that resulted in a slightly higher exhaust port. All I have seen before yours and Mark's have rounded tops. I believe the little ridge is where the outside and inside molds meet. The outside has a squared off slot that meets a rounded inside top. Possibly your's was cast with the inside mold elevated slightly. Whatever it is it matches with the melt pattern on the piston. Below to illustrate what I am talking about are photos of an NOS cylinder.

As an aside, did you notice that it appears MAC marked your cylinder as an A and then changed it to a B.

Ron

 

[rwoods]

Lest you think I am nuttier than I am, the sawdust all over the NOS cylinder is from my miter and table saws. Ron

 

[BigBlue]

May just be the camera angle or some transfer or possibly a variance in casting that resulted in a slightly higher exhaust port. All I have seen before yours and Mark's have rounded tops. I believe the little ridge is where the outside and inside molds meet. The outside has a squared off slot that meets a rounded inside top. Possibly your's was cast with the inside mold elevated slightly. Whatever it is it matches with the melt pattern on the piston. Below to illustrate what I am talking about are photos of an NOS cylinder.

As an aside, did you notice that it appears MAC marked your cylinder as an A and then changed it to a B.

Ron

View attachment 602626 View attachment 602627

Interesting info. To my untrained eye I don't see much difference between your pics and mine. Are you talking about the tip of the 'V' or the other side?

As for the piston, you think that is from heat/melting? To me it looks like something got into the cylinder and scraped/gouged the piston. But I am a total newbie when it comes to engine problems.

And yes, I did notice the "A" crossed out and changed to "B". Is that because they measured it and found that it was different than originally intended?

Rob

 

[Brian Van]

Could it be square due to the amount of wear? Maybe factory reconditioned?

 

[Brian Van]

Yeah, that's what it looks like. Sorry if the other pictures weren't great. Here's another couple views.

I want to apologize ahead of time. I can't wait to see the cylinder.

 

[rwoods]

Sorry for the one upside down picture. I was talking about the tip of the V - yours looks to be square where mine is round. Yes, I think your piston is melted. Look at the streaks to the side of the gouged out area. It may have also ingested a needle bearing or something else. You can tell better once you crack it open.

Ron

 

[Brian Van]

Ron how long do you think it could have ran like this?