Stihl 084 modification???

[aquan8tor]

I got an 084 last month to replace my fried 394XP. Turned out the 084 had a scored piston/cylinder as well. Long story short, I got a used set from a member here, Thanks Plumbcrazyjr!!! Since I'm doing almost a complete teardown and rebuild, I figure I ought to do everything to modify for performance while I have it all apart.


To start out, I thought I'd deal with the intake side. Looking in the intake port where the carb attaches, there is a little "drip" of metal that looks like a uvula ( the little thing that hangs in the back of your throat when you open your mouth wide). Anyone got pics of their own porting jobs? I'm mostly a newbie at this. I smoothed out the intake and exhaust ports a little with my 394XP, as well as a muffler mod, but never any grinding. How much real gain is there? View attachment 192675

Then, with the exhaust port, I'm just going to clean it off. I'm a little worried about doing anything serious here. For muffler modification, I'm not sure how much I can remove from the baffling inside. I need pictures; from the research I've done, it looks like there were a few different muffler configurations; the IPL and the shop manual don't clarify anything. There is the box with holes in it where the exhaust enters the muffler, and then a U shaped double pipe with the spark arrestor screen on it. Those two little tubes are pretty small, but I'd like to /try/ and keep the spark arrestor screen if possible, because the saw will be used primarily for milling. I don't have the metalworking skills to build an exhaust pipe to direct the exhaust away from the log and saw. I need pictures of anyone's build that they can show me. I've tried to search through threads here to find pictures of people's muffler modifications on an 084, but I'm coming up short. Any help out there?
View attachment 192688View attachment 192689

 

[w8ye]

The uvula is to keep the ring from catching in the intake port

 

[mtngun]

What w8ye said about the intake port.

My 084 piston rings ends do not go in the intake port, so that little tonsil is not need.

But, the little tonsil has little effect on power. Critical flow takes place at the bottom of the intake port, not the top.

The factory muffler is extremely restrictive. Modding the muffler is the easiest way to gain power.

See my 084 thread. http://www.arboristsite.com/chainsaw/133334.htm

 

[blsnelling]

I wouldn't learn porting on a super expensive 084 cylinder. You also want to get the saw running properly first anyway. Have you determined why the original piston was scored?

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[aquan8tor]

I haven't determined yet for certain; I don't have a vac/compression tester to check for leaks. I haven't removed the scored P/C yet, just haven't had time. I know I need to test before pulling the bad jug. I did find some cracking in the fuel line, which may or may not have had pinholes in it; this could be the source if it was sucking air; to be honest, while I was examining it, it was so deteriorated I tore it. I have a new line to replace it with.

 

[blsnelling]

I would plan on new crank seals and a careful inspection of all lines. Get rid of the grub screw tank vent too. Put the umbrella check valve inside the tank.

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[aquan8tor]

Mtngun, I found your build thread after posting my thread. I've been reading it since then!


Also, blsnelling, point taken. I don't want to do any grinding at all here; just polishing. I just wanted a clarification about the little extension affecting intake flow. I don't want to do anything that would change the port size or timing, just flow smoother is all.

 

[aquan8tor]

I would plan on new crank seals and a careful inspection of all lines. Get rid of the grub screw tank vent too. Put the umbrella check valve inside the tank.

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I didn't want to split the case if at all possible, but I don't want to screw up another cylinder either.

I forgot about that little tank vent. I did check it for leaks or clogging; it had a couple tiny tiny pieces of debris in it, but nothing that could have clogged it. So you're saying to replace it with a check valve? I'm not clear here. If it weren't for you guys I'd be up the creek with a POS saw that won't run.

 

[w8ye]

You don't have to split the case to put seals in

 

[mweba]

No modifications needed, they are perfect in every way.

 

[aquan8tor]

I thought gaskets was what was meant. To be clear, which seals are we talking about; are there any other than the oil seal under the flywheel that need to be replaced?? Assume that I'm an idiot here, because I feel like one regarding this saw.

 

[mtngun]

To be clear, which seals are we talking about

There is a seal on either side of the crankshaft.

Definitely worth spending money on a $50 mighty vac compared to the cost of a top end.

 

[blsnelling]

A clean but old grub screw style tank vent caused a burnt up piston on one of my 084s. The little orange valve on the bottom side is a far superior design.

If you haven't taken it apart yet, you may not even need that replacement cylinder. They can often be clean up. Before you throw it away, you can send it to me.

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[7hpjim]

No modifications needed, they are perfect in every way.

Thats what I thought too

 

[aquan8tor]

Unfortunately, I can feel pretty deep scoring. If there's any chance of salvaging it, I'm going to either learn to port on a couple beater saws, or get it ported by someone. I think it's scrap metal at this point though.



As far as the tank vent is concerned, I'm not familiar with the orange check valve type. There does seem to be a valve of some sort inside the vent, but I haven't seen any of the other valves to know what you mean. And they go into the bottom of the tank instead of the top? Do you have a photo? That would help a lot. I'm a fairly handy guy, and could do this easily if I know what I'm trying to replicate. Thanks in advance.

 

[aquan8tor]

What w8ye said about the intake port.

My 084 piston rings ends do not go in the intake port, so that little tonsil is not need.

But, the little tonsil has little effect on power. Critical flow takes place at the bottom of the intake port, not the top.

The factory muffler is extremely restrictive. Modding the muffler is the easiest way to gain power.

See my 084 thread. http://www.arboristsite.com/chainsaw/133334.htm

Did you remove the guts, or was it already done? I guess you had to braze on the spark arrestor holder if you were the one that modded it. The stock outlet is a joke; it's about a dime size square hole, fed by two smaller-than-dime sized tubes. Not a whole lot of breathing room there.

 

[blsnelling]

Unfortunately, I can feel pretty deep scoring. If there's any chance of salvaging it, I'm going to either learn to port on a couple beater saws, or get it ported by someone. I think it's scrap metal at this point though.



As far as the tank vent is concerned, I'm not familiar with the orange check valve type. There does seem to be a valve of some sort inside the vent, but I haven't seen any of the other valves to know what you mean. And they go into the bottom of the tank instead of the top? Do you have a photo? That would help a lot. I'm a fairly handy guy, and could do this easily if I know what I'm trying to replicate. Thanks in advance.

Post up pics of you cylinder. You may just have aluminum transfer. Those are valuable cylinders and are getting hard to come by.

I don't know that I have a pic of the orange umbrella. It's about a 3/8" diameter flap with a long tit on the back side. That tit pokes up through a hold where your current vent is attached, and pulls through, holding the round flap against the inside of the tank body. It's PN 1110 353 1600. You would then simply remove the grub screw from the short hose on the outside.

 

[stihlboy]

lol i love 084s i have 3 of them one won sc timberfest. good luck i hope yours works out for you. if you have any questions just ask we have a great group of guys here

 

[blsnelling]

lol i love 084s i have 3 of them one won sc timberfest. good luck i hope yours works out for you. if you have any questions just ask we have a great group of guys here

Where in the world have you been for the last 6 months!!!

 

[mtngun]

Did you remove the guts, or was it already done? I guess you had to braze on the spark arrestor holder if you were the one that modded it. The stock outlet is a joke; it's about a dime size square hole

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.