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Used up Piston/Cylinder?

Started by brettl, December 15, 2013, 12:05:03 AM

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brettl

About 5 years ago I bought a Craftsman "Professional" ::) dirt cheap. (EDIT: Turns out it's a Redmax GZ) It had never been run and I figured it would work until insurance replaced my stolen Stihls. Well, if I'd known it would last this long and run so well I would have taken better care of it. :D I've run duller chains than I would ever run on my Stihls and used it much harder than it was designed for. I've run it a bit to long and hot at times and put older gas in it rather than pour it out. I've abused it. :-\
1 day ago I was forcing it through 10" green Hedge logs and it was powering through them. It was starting hot and cold, idling like a champ and the power was great. Today, in softer wood, it runs for several minutes then just shuts down and won't restart until cool. It will pop and fire enough to turn over but won't even idle. I've worked on many worn out engines but strangely enough, I've never used one up myself to witness the process of a failing saw. But then, I've run Stihls, so maybe not so strange. ;D This is all assuming that it is the p/c losing compression at operating temperature or some other piston/cylinder damage. I haven't torn it down yet. It has good fuel, new plug, clean air filter. This seems a very rapid decline, is such a rapid decline normal in the failure of a p/c?

Al_Smith

You probabley used up the seals not the piston .

The seals are made of Buna-N a synthetic rubber .It's nearly impervious to straight gasoline but doesn't hold up well to ethanol mixed fuels .

What happens is the compound becomes hardened over time and losses its' resiliancey .After a short run they heat up and leak .After they cool down they shrink and it appears good to go,not so .

brettl

Thanks Al. Unfortunately, gas stations here don't always make clear that certain grades may contain ethanol so I'll have to assume that they do. With this in mind, is there a seal brand/type on the market that is impervious to ethanol? I've never switched to synthetic oil mix and recently read that it may not be good for the older seal types. Is this accurate? My Stihl dealer says they'll be phasing out the orange bottle in the next 3 to 4 years. Thanks everyone.

ZeroJunk

Are you sure it is not the ignition ? That is the way some act when they fail.

Al_Smith

Honestly I have no idea if Stihl has changed the seal formulation or not.The reason I say this is the last few OEM seals I bought had a bluish tint to them instead of the normal black color .I further assume that because the auto industry has changed the formulation for such things as seals for fuel injectors because of ethanol deteriation that other manufactures would do likewise .

That Craftsman could be a Poulan ,could be a Husqvarna or even a Dolmar.I myself can't tell even if I saw it . 

brettl

Is Dolmar a part of that conglomerate? I thought they were one of the few who still stood alone, although I know Makita is selling blue Dolmars. I thought about the ignition to and will check it if the compression test shows normal.

Ianab

Sachs Dolmar was completely bought by Makita in 1991, so the saws are now effectively the same, apart from the colour.

Dolmar may certainly have built saws for other companies, but currently they are part of the Makita group.

Ian
Weekend warrior, Peterson JP test pilot, Dolmar 7900 and Stihl MS310 saws and  the usual collection of power tools :)

Al_Smith

Sears being Sears you never really know who made what until after the fact .Over the years I can think of several saws they sold under their brand name .Two really familiar are the McCulloch pm 610 and the Poulan s-25 .More than likely 3 or 4 dozen or more .

CTYank

I'd suspect fuel or pulse (if it has one) lines. Not really a p&moan thing from ethanol- cheapie Poulans had OEM lines made of plastic (vinyl?) that got really brittle really quick. When they fail, carb will suck dirt, so plan on rebuilding carb.
I'd sure make a compression test before pulling the top-end apart. One expert says that a piston should last for two rings (or sets of same). If you hosed the top-end, you might get lucky and just need a new ring. Just from pulling on the starter, you should be able to do a crude compression test.
Sharpening chains is so easy, there's really no excuse.
Sears' model # can ID the mfg.
'72 blue Homelite 150
Echo 315, SRM-200DA
Poulan 2400, PP5020, PP4218
RedMax GZ4000, "Mac" 35 cc, Dolmar PS-6100
Husqy 576XP-AT
Tanaka 260 PF Polesaw, TBC-270PFD, ECS-3351B
Mix of mauls
Morso 7110

bandmiller2

Like most sears stuff they have good,better,and best.For a wile they were selling Dolmars as their best.
A man armed with common sense is packing a big piece

brettl

I'll take a look at the model # when I'm back home and do a compression test so I can get more facts into this thread and less speculation.
I can say that it looks nothing like any Poulan or Mac I've seen. No primer bulb, bar oil and gas cap one over the other just in front of the handle and a contoured air filter cover held on by a single plastic nut, identical to some Blue Max pics I see. Don't know who makes or sells Blue Max(I'd never heard of them until this evening.)
What about the danger that synthetic oils may pose to older seals that I brought up earlier? I read of it in some other threads here but no definitive answers so far.

Al_Smith

I'm not certain if in fact synthetic oils pose a problem or not .I've never heard of any .

brettl

Of all things, I haven't been able to find a fitting to match the plug threads >:(, so no compression test yet. But as to the debate on who made this one, I've found pictures of a Redmax GZ4000 and GZ4500 that are absolutely identical except for color.

Al_Smith

It's probabley an M10 thread  instead of M14-1.25 like the rest of them .

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