Author Topic: Stihl 084  (Read 7443 times)

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Offline Al Smith

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Re: Stihl 084 AV dies at idle
« Reply #40 on: November 10, 2011, 10:28:28 am »
You could possibley have a leak in the impulse line but usually if so it won't run long in high speed .On the idle circuit just in what the fuel chamber holds on a saw the size of an 038 it will idle 10 minutes with a dry tank .You almost think it is going to run forever .

Offline mike84c

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Re: Stihl 084 AV dies at idle
« Reply #41 on: November 10, 2011, 10:40:33 am »
Yea, I tend to agree with that.  I replaced the impulse line with a piece of clear tygon, and it still is the same.  I'm starting to think it may not be the carb, as I was running in on the ground with the air filter off, and kept opening up the low speed needle, as I kept goosing the throttle to keep it going.  I could get the low speed condition so rich that gas droplets were spraying out the carb intake, which means to me, the low speed circuits are functioning.  I'm thinking about pulling the cylinder off and seeing what I see.  what compression should this saw have cold?  anyone know?
thanks
Mike

Offline Cut4fun

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Re: Stihl 084 AV dies at idle
« Reply #42 on: November 10, 2011, 01:18:14 pm »
My good running stock one with a lot of time on it was holding 145psi last time I checked it before selling. Keep pulling till the needle doesn't move up anymore on gauge to check.
REDNECK Saw Repair

Offline Al Smith

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Re: Stihl 084 AV dies at idle
« Reply #43 on: November 10, 2011, 01:50:34 pm »
Low comp won't make it die on the vine .I wouldn't worry too much about it unless you can pull it over easily without the decomp .Even then keep in mind that's a static reading  which could jump quite a bit once the engine is running

That thing just isn't getting fuel through the low speed jet for some reason .

As far as the carb ,I've never worked on that model so I know little of nothing about its' praticuler whims and where fors .I've had carbs run with just the low speed but never had one the wouldn't suck gas though the low speed .--Unless that thing has a bolted butterfly with a slot that came loose .If so on some carbs if that slot does not align with the fixed jet /nozzle they won't idle .

Offline mike84c

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Re: Stihl 084 AV dies at idle
« Reply #44 on: November 10, 2011, 01:56:28 pm »
I'll look at that and see if the holes in the carb bore are plugged off by the throttle plate, although I have already put two layers of tape on the idle screw to increase the idle, and stuck a small screwdriver under the throttle to increase the idle, and in all cases, she dies just the same

Offline man of stihl

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Re: Stihl 084 AV dies at idle
« Reply #45 on: November 10, 2011, 06:21:25 pm »
service manual says. Engine stalls at idle speed, but operates normally at full throttle; oil seals leaking or manifold leaking. I hate to say it but it sounds like you have an air leak. If the new carb is giving you the same symptoms..... That 365 poulan i had was doing the same thing. would run wide open but wouldn't idle. It ended up needing bearings and seals.
Ron

Offline mike84c

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Re: Stihl 084 AV dies at idle
« Reply #46 on: November 10, 2011, 06:32:13 pm »
that sort of makes sense.  I will do a pressure test and see where its leaking, unfortunately I have to make up an exhaust and intake cover.  will let you know what I find
Mike

Offline w8ye

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Re: Stihl 084 AV dies at idle
« Reply #47 on: November 10, 2011, 09:20:14 pm »
This statement by you . . . .

"I'm starting to think it may not be the carb, as I was running in on the ground with the air filter off, and kept opening up the low speed needle, as I kept goosing the throttle to keep it going.  I could get the low speed condition so rich that gas droplets were spraying out the carb intake, which means to me, the low speed circuits are functioning."

Makes me think you have seal or other crankcase pressure integrity problems if the intake side of your piston is not trashed?

I've had carbs with the intake circuit plugged and I could never get any droplets spitting out the carb from the low side.

Offline Al Smith

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Re: Stihl 084 AV dies at idle
« Reply #48 on: November 11, 2011, 07:21:11 am »
Usually they will idle with a seal out but they often won't with a tear in the boot .

What's with that tape on the low speed screw ? If that thing is sucking air through a wibbley woobley screw I doubt it would work too well .

Offline mike84c

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Re: Stihl 084 AV dies at idle
« Reply #49 on: November 11, 2011, 08:37:49 pm »
The tape on the throttle screw was just an idea by one of the forum to increase the dia of the throttle screw to hold the butterfly open more, it didn't help.  I ran a pressure test on the engine.  sealed up the carb side with a piece of inner tube between the carb and manifold, sealed up the exhaust side with a piece of inner tube between the exhaust and cylinder.  clamped the impulse line, and installed my leak down tester in the spark plug hole.  Pressurized to 10 psi, and it held rock solid.  I pulled the flywheel (what a pain it the butt, I guess its never been off), and pulled the cluch and bar oil drive.  I sprayed both seals down with soapy water.  No leaks, and as I said, it held 10 psi rock solid.  I also hooked up my vacuum pump, and pulled a vacuum, and it held that also.   There is no play in either the clutch side bearing or the flywheel side bearing.  Didn't put a dial indicator on it, but as I said, absolutely no play......So I'm guessing its not a crankcase or seal leak.  Not sure where the manifold leak would show up, but I'm thinking its not it.  Yikes.... I'm not sure where else to look.  Anybody?
thanks
Mike

 

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