Stihl 084 modification???

[aquan8tor]

Mine had no guts other than the internal spark screen. I guess there were several different mufflers made for the 084.

Hard to see what's going on in your muffler pic, but anything you can legally do to open up your muffler is a good thing. The spark screen is a restriction, too, only flowing 25% of its area.

Just be gentle with the muffler because replacements may be hard to come by.

In the IPL there are two mufflers listed; the USA model, and the standard. So we get the crap end of the stick then. I'll get a better picture later. There is a little perforated baffle directly over the exhaust port, then the two U tubes after the screen. I had removed the spark screen on my 394, but I DID once start the bark on fire on a really dry log while milling. It was easy to put out, but it left me feeling a little nervous. I don't know if it was the length of the exposure to the hot exhaust, or a spark that passed through the muffler. I'm inclined to think it was the long exposure to the hot exhaust, because I'd removed the felling dogs to give more capacity on the mill, making the exhaust a couple inches closer to the log. I guess after I gut the muffler, if I use it or not will be determined by how easy it is to re-mount the spark screen.

 

[aquan8tor]

as promised, here's a better picture of the muffler. I'm going to go down to the auto parts store and get a vacuum tester before pulling the jug. Got to wait til I pay this month's bills first. Next week. I actually have a vacuum pump, but I think its a bit too powerful to use for this purpose. I have to fabricate some sort of plate to seal off the exhaust and intake anyway; I don't have the special Stihl plates described in the shop manual. Sorry for the crap in the background. It's sitting on the bed of my wood lathe. View attachment 192759

 

[mtngun]

I have to fabricate some sort of plate to seal off the exhaust and intake anyway; I don't have the special Stihl plates described in the shop manual.

I made plates out of scrap metal, and matching neoprene gaskets. But you can just use a piece of neoprene (or inner tube) between the muffler and the jug. Ditto on the carb side.

The decomps usually leak slightly and have to be plugged in some fashion for the test.

Boy, that is a funky looking exhaust system. What were they thinking ?

 

[aquan8tor]

Yeah the exhaust is seriously ridiculous. The square hole is only marginally larger than either of the two U shaped tubes that dump into it. We'll see if I can loosen them with a torch and open it up a lot. I may just leave the tubes in place and remove the screen, as well as cut open the outlet about twice the size it is now. I'm a bit apprehensive about messing with it too much, but I'd really like to weld on a short piece of 45deg. pipe to aim it up and slightly to the right; meaning away from the log and me at the same time.

EDIT: on the decomp; I know all of them leak a little, but the one on the scored cylinder must have leaked a fair amount, because there is hole melted in the plastic next to it. The original owner used it for milling in BC.

 

[gunnarfan]

thanks for this and the references to other 084 threads. i've been having some long talks with mine about how its going to deal with its mid life crisis.... not planning on retiring any time soon.

 

[Nardoo]

I used an 084 for 12 years as my primary saw cutting an awful lot of wood. Admittedly, in Oz we have very good flowing mufflers fitted as standard but at no time did I ever think I needed to do a port job for more power. A good 084 will cut some big, hard wood at a good speed and do it year after year. After year.
I just reckon they are pretty darn good as is.

Al.

 

[mtngun]

at no time did I ever think I needed to do a port job for more power. A good 084 will cut some big, hard wood at a good speed and do it year after year. After year. Al.

There is no such thing as too much power for milling. In stock form, the 084 is a dog, making no more power than an 066.

 

[blsnelling]

In stock form, the 084 is a dog, making no more power than an 066.

I agree entirely.

 

[aquan8tor]

Well, I found out today how expensive these darn parts are. $28.00 each for 2 piston rings, $22.00 and $6.00 for the crank seals. $39 for MityVac vacuum tester. Haven't nailed down the leak yet, but I'll find it. I only established that there's a leak. It got dark before I could use the spray bottle. Running saw, here we come. I'll post pics of the muffler as it comes along.

 

[mtngun]

Well, I found out today how expensive these darn parts are. $28.00 each for 2 piston rings, $22.00 and $6.00 for the crank seals.

Suggest Caber rings.

Baileys has their house brand flywheel side seal for $4. They don't have a house brand for the clutch side, though. Yep, parts for 120cc saws have high mark-up.
Bailey's - CRANKSHAFT SEAL 15MM X 29.6MM X 4MM

 

[aquan8tor]

Suggest Caber rings.

Baileys has their house brand flywheel side seal for $4. They don't have a house brand for the clutch side, though. Yep, parts for 120cc saws have high mark-up.
Bailey's - CRANKSHAFT SEAL 15MM X 29.6MM X 4MM

Already paid for the rings; if I'd known the Caber ones were available I would've popped on them. The flywheel side seal was only $6 for Stihl brand, but the clutch side was $22. I'm just glad I didn't have to get the whole cylinder/piston assembly. Sheesh!