Author Topic: 125 Mac with a tummy ache .  (Read 565 times)

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Offline Al Smith

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125 Mac with a tummy ache .
« on: September 01, 2011, 02:16:21 pm »
Dang the big old saw swallowed something that didn't agree with it . Luckily it was when it was being cranked over and not up to speed .

Turns out it was part of the clip that holds the choke rod in place . Part of it was laying on top of the reed and a little bit got sucked in through the center upper transfer hole which is right under the reed .

I rolled it over backwards to free it up then tore down the engine .On a reed valve Mac that's a couple hours in itself .They aren't easy like a 10 series .

It took me about an hour and a half to carve loose the rings  with a razor blade .It isn't like you can find these things like they're a late model Stihl ya know .Being tool steel though they're very tough .

Sanded the gouge out of the piston and used a nail file to true the ring grooves .

A little low spot in a piston especially a full skirt doesn't hurt them much .A high spot however will break the surface tension of the oil film and usually will fail .

Any way ,back together and running .

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Offline Cut4fun

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Re: 125 Mac with a tummy ache .
« Reply #1 on: September 01, 2011, 02:23:20 pm »
Al it sounds like you better change the diet food your feeding those Macs  :o.  Lucky indeed  8).

Offline Al Smith

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Re: 125 Mac with a tummy ache .
« Reply #2 on: September 01, 2011, 02:54:53 pm »
I might point out on the older series of Macs both piston port and reed valve that the air filter was the weak link .

It was only a single thin membrain that went between the air box and the cover .It had plenty of surface area but didn't stop stuff from being sucked into the carb ,chips, nuts ,bolts .More modern saws of course totally close off the path of junk bypassing the filters . You have to remember the time period on these things though .They were just about the same system of most saws of the time period .

Just about every Mac I've ever worked on with any hours on them shows some signs of dust ingestion on the intake side of the piston skirt .Doesn't seem to hurt them though .This by the way is not the only one I've managed to save that swallowed something .

Offline Cut4fun .

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Re: 125 Mac with a tummy ache .
« Reply #3 on: September 01, 2011, 03:02:28 pm »
I seen a husky 3120 work saw suck a bolt inside the air filter area north of me and it got caught between the crank and crankcase and busted a hole through the crankcase.

Also seen a partner 5000 suck a modified air filter cover nut into intake and lodge under piston on down stroke. It wasnt pretty and it wasnt mine.   ;D

Offline Al Smith

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Re: 125 Mac with a tummy ache .
« Reply #4 on: September 01, 2011, 03:30:47 pm »
Some of those Walbro's used on the 10 series Macs had a nasty habit of spiting the little bolt out that held the throttle butter fly in the carb . I sucked one right through a 70 cc  6-10 once and never put a mark on the cylinder or piston .

Had some size of Stihl that blew a circlip right on top of the piston .How in the world it ever did that I'll never know .

I've also had pistons literally grenade on Stihls and never put a mark on the cylinder .Must be magic or something .