STIHL CHAINSAW EXPERT NEEDED

[JWMUSTANGMAN]

Sorry guys. I know I said I'd get some pics and more info this past weekend, but it didn't happen. Had some family health stuff come up. Looks like my saws will have to take a back seat for a week or 2. I'll probably look into them one at a time and maybe start a thread for each to keep them separate? What would be best? Also, what type of tester would you all recommend for the pressure/vac test? Cheaper the better.

 

[berrnard]

Sorry guys. I know I said I'd get some pics and more info this past weekend, but it didn't happen. Had some family health stuff come up. Looks like my saws will have to take a back seat for a week or 2. I'll probably look into them one at a time and maybe start a thread for each to keep them separate? What would be best? Also, what type of tester would you all recommend for the pressure/vac test? Cheaper the better.

I think all of us here use the mity vac 8500. Usualy $60ish


Stihl 025 for sale
Stihl 250 for sale
Personal Saws
Stihl 201t
Stihl 260 pro
Stihl 460

 

[pioneerguy600]

Like above post, may as well buy the 8500 and make it the one and only you will need as it does both pressure and vac.

 

[JWMUSTANGMAN]

I think all of us here use the mity vac 8500. Usualy $60ish


Stihl 025 for sale
Stihl 250 for sale
Personal Saws
Stihl 201t
Stihl 260 pro
Stihl 460

sounds good. I think I can swing that. Will it test compression pressure as well? or will I need another tool for that?

 

[pioneerguy600]

No, a compression tester is a totally different tool. Best to get a comp tester that is specifically made for two stroke equipment. An automotive comp tester will register a much lower comp reading unless one changes out the schrader valve in the part that screws in the sparkplug hole.

 

[JWMUSTANGMAN]

got it. Is the compression tester something I'll need right now as well?

 

[pioneerguy600]

I would say no, not until you inspect the condition of the piston, take the cover off the muffler and have a look at the piston, if there are vertical scratches or streaks then that usually means the engine is scored and will need to be torn down. If the piston looks clean then just try to get it started and running next.

 

[JWMUSTANGMAN]

cyl wall is scored. I have looked at that. so where to from here?

 

[pioneerguy600]

If there is scoring visible then there is no recourse but to tear the engine down, remove the cylinder off the saw and get us some picts, some times the cylinder can be cleaned up and a new piston and rings installed. Many say to pressure and vac test the saw before removing the cylinder as the cause of the scoring should be determined first.

 

[pioneerguy600]

I will add that most times I do not test first, I make sure the new parts are properly installed and do the test before installing the muffler and carb. If the cylinder base is sealed properly at the time of install then the rest of the air leak points can be found as the saw is reassembled.

 

[HarleyT]

Generally it is a good idea before ordering parts, etc, to know if and where an air leak is at.
Especially if you put the saw all back together with new parts, then finally discover that you have to tear it all down again, then lern how to and buy tools to split a crankcase..

 

[JWMUSTANGMAN]

so what is the thinking? How would bad crank seals cause the damage? Air leaks past crank seals, then finds its way into the comb chamber, then causes lean condition? That causes excess heat and expansion of the piston? Boom, cyl walls scored?

I'm sorry. I've just always been one for wanting to know the how and why; not just that it happened. haha

 

[HarleyT]

It is a condition called a lean seizure, which can be caused by a dozen different causes.

 

[HarleyT]

One can lean/seize a brand new saw by just playing with the carb screws.

 

[HarleyT]

On chainsaws, by lessening the fuel to the fuel/air mixture, one can make the rpms raise to over 16,000 rpms or more.
Which in itself raises the temps. But combined with the lessening of lubrication {oil is in the fuel mix}, the temps raise exponentially, and the aluminum piston starts to melt.
So a cracked fuel line, gunk in the carb, etc., and so on, can cause a lean seizure, and of course a leaking crankcase seal.
But some of the guys here are a little over fixated on the seals, and jump to that before checking more common causes.

 

[HarleyT]

So I always try to get the O.P. to slow down, don't waste money, and find out the underlying cause of the failure, and then fix the problem properly.

 

[JWMUSTANGMAN]

Makes sense. The same is true in a 4 stroke V8. I remember that from when I dirt track raced. We would always tease that a car was fixing to blow up if it was running really good. We always said they run the best right before they blow. Most of the time, its true. Not always due to a lean condition, but I digress. Anyway, I do remember the saw "running like a scalded dog" right before she siezed up. I was in the middle of a cut through about a 2' diameter red oak. It was chewing through just dandy and then it was like a shot of NOS hit it. It revved really high and sawdust was flying! but before I realized what was going on, processed it all, and decided to shut it down, it just bogged down and stopped.

 

[HarleyT]

Anyway, I do remember the saw "running like a scalded dog" right before she siezed up.

I have heard that line many, many times.

 

[JWMUSTANGMAN]

I have heard that line many, many times.

And in those cases, what did it end up being? Was there a common answer? or did they all vary a lot?

 

[HarleyT]

Bad fuel lines, crap in the carb,someone playing with the carb adjustments,
mostly.