Running saws with loose mufflers

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Ax-Man

Ax-Man

Don't make me chop you
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I should be able to answer this question without having to post a thread but I am going to post it anyway.

I have two saws with this loose muffler problem . One is a 200 and the other is a 076. I have tried to fix both these saw by tapping and threading the holes in the cylinder for the next larger screw or bolt. It works for awhile but the problem comes back after time. You can only get by doing this a few times before you run the risk of getting the cylinder wall to thin and that is where I am at now with these two saws.

The 76 has had this problem since the day one which was probaly twenty years ago. I bought it used as back-up for my other 076 that I bought new. The 76 with the muffler problem has always been a good saw if it wasn't for this muffler problem. We have used it on the job and as a noodling saw. We have ran it with this loose muffler for years with no problem. Last year I fixed the muffler problem again and started using the 076 as a milling saw, but now the problem has come back again when I started milling again this year..:cry::cry:

I guess the question to be answered is if a saw is run with a loose muffler are you creating a super lean running condition that will eventually lead to the engine finally giving up due to be running to lean. I have enough parts to fix both these saws with used cylinders but time is limited these days because of my aging parents needing more of my time if you know what I mean.
 
One thing I have experienced with a loose muffler, is the saw catching on fire from unburnt fuel not exiting properly and igniting from the heat of the muffler. I suspect the additional oxygen available in the presence of the heat is the problem. It happened twice in one day with the 020 before realizing what was going on, and once after refueling where there was a bit of spilled fuel present too. No joke and hard to extinguish, I was a moment away from giving the saw a heave. It was a visual lesson in the fact that there is definitely a quantity of fuel that is in the exhaust.
 
Could one permanently Locktite in studs and the muffler be secured with nuts? Easier to keep a nut tight, perhaps, with some thought?
 
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Hmm, that might work for the 076. I'll have to see if I can find the right studs.
 
I had some luck with lock washers on Huskys, but never tried it on the Stihls. I did notice that if I used a new bolt, they held better. Probably due to the little cuts on the back of them being freshand helping lock them :dontlnow:
You'll have to excuse me, I need to go pull the muffler off the 036 now... screw loose from yesterday .....
 
Originally if I'm not mistaken those Stihls should have had belleville type washers on the muffler bolts .

A belleville is a type of washer that keeps a steady tension on the bolts regardless of it's expansion due to heat .Fact they are used on many more modern aluminum auto engines as well as electrical connections when aluminum is used as a current carrying conductor .

If I remember I'll snoop around at work through the parts drawers and see what I can find .
 
Al is right on the Stihl muffler bolts.

I have used the high temp Locktite for years on big vibrating saws like the 076, 041, and a bunch of McCullochs. Main prob is when usin' said Locktite... when you actually need to get the muffler off... it's a bitch.

Gary
 
I looked them up and they aren't that costly unless you get the precission type .Mc Master -Carr .You'd want what ever size the bolts,probabley 6 MM by whatever the width of the torx head Stihl bolt is .
 
Just out of curiosity have you tried tightening them just a bit after the saw is warm?
I have a 288 that just wont quit. Any way I had the same issue with this saw as your having. Until I replaced the bolts, painted the threads with black high temp paint, put them back in, tightend, let the saw warm up real good & with out being to aggressive tightend a bit more. No trouble since doing this.
 
Paint makes a great thread locker. On my rifles with adjustable triggers, I set my trigger weight with a machine screw in the trigger system, and lock that screw tight with a dab of nail polish.
 
Thread locker of a sorts works .However a threaded fastener taken to the yield point will not unscrew unless a certain amount of expansion is present in the material .

Not to try and sound like a smart ass but it's part of a job I do every day is annalizing suspected possible fastener failures .A threaded fastener ,bolt if you will acts the same as a spring under tension .You take that fastener to the point you actually stretch the bolt .One reason they use a bellville or other types of devices is to allow for expansion of the aluminum in the point of the female portion of the thread connection .A lock washer will work to a point but only to a point of conditions such as the amount of heat present in the area of the exhaust port .

If you remove the bolts of just about any modern aluminum automotive engine you will either see a bellville washer or a captive bellville type on nearly every bolt in that engine except the head bolts,mains ,rods .Even the valve covers use a type of captive washer system . If you think about it no matter who made that engine they don't leak oil like the old Chevy small block 350's .That's just the way it's done ,no thread lockers .
 
Here's a solution I've used often for repairing stripped threads. Heli-Coil {link} -- they are easy to use and come in almost every size. You can get them with a self-locking feature that should be a long-term solution to your problem. I've even used them to rethread stripped spark plug threads. I can highly recommend them.
 
I used helicoils for years but I think a Timesert is a lot better for most of my stuff now.

Not knocking them at all, just found Timeserts better for some things.8)
 
Hey SoonerFan: Forgot your name again. :|:

I just wanted you to know that I'm way out of my field of--well I won't say "expertise", (I'm a bit on the mechanically ignorant side) work. ... anyway......

I guess I just wanted you to know that the shop that I work for runs saws absolutely into the ground. When I say "runs em into the ground" I mean that the 200 T whose muffler has completely fallen off is just considered to be finally "broke in". :lol:

They generally run like that for a couple of months till they don't really have sufficient back-pressure to keep idling well, (I realize, btw, that this doesn't make any sense. I mean: if there isn't enough back-pressure to keep them idling well "after a while," then how can there ever have been enough to have them idle well with no muffler. I don't know how, but it seems like they do. Am I now, here, inadvertently answering your question?) and then, finally, John Emmonds, our head saw guy, swaps out some parts to limp them along, or builds a "new" saw out of tons of spare 200 T parts. I've never heard the term "leaning out too much", and I don't believe--I cld be very wrong here!--that the lack of back-pressure cld cause the two-cycle oil to fail to do it's job, and so fry the piston/cylinder. Is that even what you're asking about?
 
The oil doesn't fail just the mixture ratio .The muffler acts like a pressure regulating device .Once the internal muffler pressure equals the incoming transfer pressure the fuel /air mix ceases to exit the cylinder .

Now if you don't get a "clean " transfer you have a partial cylinder with unburned exhaust gasses which limits the power the engine can produce .

Conversally if the carb is tuned a tad too lean and you have relieved the muffler pressure to an extent you could possibley get a cylinder where the gasoline and air ratio ,not the gas /oil ratio is too lean .Lean mixtures burn hot so that's one way to cook a piston .An air leak through a faulty boot ,faulty crankcase seal will basically do the same thing which is lean the fuel/air ratio and cause a lean burn condition .

Often times when people make mention of reworking a muffler they caution to retune the saw carb so as not to get a lean run .
 
Hey! Sorry Dennis!

Just re-read that post I sent you and I think that I got more confused than you! I better lay off the Mongoose I.P.A. I only had two!!

When I asked, "Am I now, here, inadvertently answering your question?" I guess, what I was driving at is that, it would indeed seem that running a 200T with no muffler whatsoever for an extended period is a bad thing. What I can't understand is why they should initially run so well (I'm talking about a three or four month period.) once the muffler has fallen off.

Sorry about my rambling mouth. I'm almost never on the Treehouse these days, but when I am, I can't seem to shut up! Don't make sense neither.
 
If you let the muffler fall off of a 200T you'll burn the plastic shrouding which is under the muffler .Geeze those things have holes through that shrouding so you can reach the muffler screws .It's nonsense to let one rattle apart like that .

Oh it will probabley run to beat hell for a period of time until you cook the piston .Then you're pretty much screwed because you didn't tighten some screws.

Here's another thing if you let one rattle apart it stands a good chance of messing up the threads in the cylinder .One of Toms 020T's was so bad I had to take it out to the next size which is 6 MM .
 
Thanks Al.

Funny thing is: John said that the pistons and jugs were always fine. We run Valvoline two-cycle. Your right about the plastic though.
 
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