084 Troubles

[T Berry]

looking for compression #'s on the 084AV, buds having trouble with his, idles and accelerates fine but when you lean on it in the cut you can stop the chain. Neither of us are mechanics (shade tree yes) so we started with compression and 130 is all we could get. He did have the jug off and said everything looked fine to him inside, piston, rings cyl walls all looked good. New head gasket. 130 sounds low but thats why I'm asking.

Tom

 

[blsnelling]

Does your comp tester have a Schrader valve at the tip? It must to get a proper reading. If so, that is quite low. I'd throw a new set of OEM rings in it since everything else looks good.

 

[Four Paws]

New head gasket. 130 sounds low but thats why I'm asking.

Some of the saws have 2 different base gaskets - .5mm and 1mm. If you put the thicker gasket on a saw, it will obviously have less compression. The thicker gasket is used to reduce compression and prevent pre-ignition where only low quality gas is available - the rainforest.

Make sure the right gasket is installed. If it is, re-ring the saw like Brad said. If you still have problems, look at the clutch and drum.

 

[Lakeside53]

At 130 an 084 still cuts... bigger saws do that.. but it it really is 130 it's well on the way out.

First, make sure the comp tester has a schrader valve right where it screws into the cylinder. If it doesn't you're reading low.

Check the ring wear by taking them off the piston (carefully...) and putting them in the unworn portion of the cylinder. Check the gap... over 18 thou and I'd be replacing them for sure.

 

[T Berry]

Does your comp tester have a Schrader valve at the tip?

Schrader valve is located on the guage block

Some of the saws have 2 different base gaskets - .5mm and 1mm.

I will check with him on gasket tomorrow

Check the ring wear by taking them off the piston (carefully...) and putting them in the unworn portion of the cylinder. Check the gap... over 18 thou and I'd be replacing them for sure.

Very good info, thank you

Sounds like first thing to do is locate another tester and start again. Thanks fellas, I will keep updating our progress.

 

[Lakeside53]

Most compression testers have a valve at the gauge block; the small engine type have another at the tip.

if you do have the wrong type, I'm betting your compression is fine. 145-155 is typical for mid life. 160-170 new..

 

[Oldsawnut]

Sounds like the carb is running lean to me.... Try to back out the h screw more usually you lightly bottom it out then back it out one turn for a starting point. There are a lot of threads on here about carb adjusting. Good luck

John

 

[Lakeside53]

Good point... but be careful tuning the 084... it MAY have a limiting coil on it.

 

[Frank Boyer]

What should a 084 wot be?
THANKS

 

[Lakeside53]

That's the problem.. with an 084 that limits, you can't use the "WOT" method.. more like 11k plus 1/2 turn more etc... Check plug and in-cut.

Without limiter, just tune to 11,750 to 12,250 with a medium length bar (for an 084). Then check in the wood and tweak as req. The "max" is supposed to by 12,250 or 12,500 depending on the coil you have, but it won't cut any better by pushing the last few hundred rpm... stay a tad rich.

 

[teacherman]

Some of the saws have 2 different base gaskets - .5mm and 1mm. If you put the thicker gasket on a saw, it will obviously have less compression. The thicker gasket is used to reduce compression and prevent pre-ignition where only low quality gas is available - the rainforest.

Make sure the right gasket is installed. If it is, re-ring the saw like Brad said. If you still have problems, look at the clutch and drum.

One of my 084s does not have a cylinder gasket, just some kinda hitech sealer goo. Talk about compression! CLAFBOH! (really cuts well) Starting it without the comp button is a true athletic event hahahaah ouch

 

[Lakeside53]

One of my 084s does not have a cylinder gasket, just some kinda hitech sealer goo. Talk about compression! CLAFBOH! (really cuts well) Starting it without the comp button is a true athletic event hahahaah ouch

170+... but at least you now have an elastostart. You should have tried it without! It was hard to get an accurate reading - too damn hard to pull over!

 

[teacherman]

Credit where due

170+... but at least you now have an elastostart. You should have tried it without! It was hard to get an accurate reading - too damn hard to pull over!

Sorry, Andy, forgot to give credit where due. What a beast! I am going to make it into a motorcycle cuz it's too much saw for me. hahahahah J/K

It would make a heckuva tree saw with the 20" bar I got for it :greenchainsaw:

 

[blsnelling]

One of my 084s does not have a cylinder gasket, just some kinda hitech sealer goo. Talk about compression! CLAFBOH! (really cuts well) Starting it without the comp button is a true athletic event hahahaah ouch

I measured the squish on a couple of my 084s. They were both .043"-.045". Removing the base gasket would not be an issue at all on either one. I intend to do tha one of these days, along with a few other mods

 

[teacherman]

Compression wood increase greatly

I measured the squish on a couple of my 084s. They were both .043"-.045". Removing the base gasket would not be an issue at all on either one. I intend to do tha one of these days, along with a few other mods

If there are 25.4 mm per inch, then .043 X 25.4 = 1.09 mm, right?
If the gasket is 1mm thick, then it seems we would want to have a certain thickness of sealant to allow for expansion of the piston. How thick wood a torqued-down layer of sealer goo be????

How much of an issue is the buildup of carbon on the piston crown? J/C

Also, does the same principle apply on the huge saws regarding muffler mods?
(about 85% of port area) I can see a cool-looking set of pipes on one of these:greenchainsaw:

 

[blsnelling]

I don't think the thickness of the sealant would be significant enought to measure. I'm shooting for .020" when I mod my 084.

 

[teacherman]

I don't think the thickness of the sealant would be significant enought to measure. I'm shooting for .020" when I mod my 084.

That's kinda what I wooda thought. Maybe some copper sheet coud be cut into a gasket about .010". That's what my old Yamaha 650 head gasket was made of, if I remember correctly. Man it can get complex when we start messin with stuff, but I guess that is half the fun.

Wait'll you see the muffler mods I have planned for the 084s. I might make that pretty one you sold me look like a Harley. LOL:chainsawguy: :chainsawguy: :hmm3grin2orange:

 

[blsnelling]

I won't be using a base gasket at all when I mod mine. I'll be lowering the jug .023"-.025", so I'll have to take an additional 0.003"-.005" off the base of the jug. I'll then install it using ThreeBond sealant.

 

[teacherman]

O I see

I won't be using a base gasket at all when I mod mine. I'll be lowering the jug .023"-.025", so I'll have to take an additional 0.003"-.005" off the base of the jug. I'll then install it using ThreeBond sealant.

I never thought about shaving the jug. COOL Hope to see a play by play!!!!!!!

That will be high performance fo sho!

 

[blsnelling]

I never thought about shaving the jug. COOL Hope to see a play by play!!!!!!!

That will be high performance fo sho!

Oh boy, are you ever in trouble. I'm afraid I just promoted you to the next level of CAD!!!!!!!!!!!!! I've done some play-by-play mods to my 460 and 260 a while back. Check my old threads.

Just wait until you run a good woods ported 084. It takes real effort to stop a 36" full comp chain in hardwood. I made the mistake of running Cut4Fun's and you see what happened to me. Let's just put it like this. It's addictive power!!