Author Topic: Stihl Chainsaw AV Design and Possible Boot Problems  (Read 272 times)

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Offline 660magnum

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Stihl Chainsaw AV Design and Possible Boot Problems
« on: October 17, 2013, 10:03:50 pm »
I'm a great admirer of the older Stihl PRO chainsaw line like the 026, 036, 044, 046, 066, & 084. They had their problems but some parts combinations of these earlier saws were really great running like the early 066 top end on a latter 066 crankcase or the 10mm wrist pin 044?

I've been told that if you get a Stihl hung up to not jerk on the handles or the carburetor boot will tear because the carb is part of the handle? So I was careful but didn't realize the movement until I saw this video. The subject of the video is a hydraulic Dyno and the Stihl 460 is mounted by the bar. So the handle part is free hanging. Nice project BTW.

Watch closely this video at the very beginning and at the very end as the handle and carb area of the chainsaw literally jumps around when his hand is not on the handle. While the chainsaw is doing this, the carb boot is really being stretched.

http://www.youtube.com/watch?v=VGpxVzkYU70

Here's another video of the saw in normal use and I cannot spot any major flexing between the crankcase and handle area but I realize a lot of vibration is absorbed anyway by the AV buffers and there is flexing of the boot but on a smaller travel higher frequency.

http://www.youtube.com/watch?v=Fp9yJvyd2rY

Other brands of PRO saws have the carb box area mounted on the crankcase with a buffer between the carb and the carb cavity area. So jerking on the handles has no effect upon the carburetor isolation rubber boot.

 
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Offline jmester

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Re: Stihl Chainsaw AV Design and Possible Boot Problems
« Reply #1 on: October 18, 2013, 07:08:37 am »
I have ran a bunch of pro stihls. And have yet to tear a carb boot. And most guys I have seen that jerk on there saw bend the wrap handle and tear there AV mounts. Imo. I feel that  most of the problem is that no one ever changes the rubber AV mounts and that causes the saw to be sloppy from the tank to the engine. With older saws i think the boot dry rots over time from the heat then with all the flex that happens there they tear. Imo
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Offline 660magnum

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Re: Stihl Chainsaw AV Design and Possible Boot Problems
« Reply #2 on: October 18, 2013, 09:47:20 am »
Jason,

That could very well be part of the problem
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Offline jmester

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Re: Stihl Chainsaw AV Design and Possible Boot Problems
« Reply #3 on: October 18, 2013, 07:16:15 pm »
I have come to like the new av spring mounts. Feel like they will hold up better over time. I have seen that if you jerk on them you can bend the spring and have things out of wack that can also put unwanted tension on the carb boot and impulse line.
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Offline jmester

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Re: Stihl Chainsaw AV Design and Possible Boot Problems
« Reply #4 on: October 18, 2013, 07:48:03 pm »
it would be interesting to see a new saw run with the handle suspended like that and see if they do the same thing.
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Offline 660magnum

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Re: Stihl Chainsaw AV Design and Possible Boot Problems
« Reply #5 on: October 18, 2013, 07:53:12 pm »
I think with the saw suspended by the bar and the handle hanging free - harmonics quickly take over and exaggerate the movement.

The moment he touched to handle, all the movement stopped. 
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Offline jmester

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Re: Stihl Chainsaw AV Design and Possible Boot Problems
« Reply #6 on: October 18, 2013, 08:46:28 pm »
 I agree. Tried to find a husky on a dyno video, just to see how they compared but could not find one.
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Offline 660magnum

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Re: Stihl Chainsaw AV Design and Possible Boot Problems
« Reply #7 on: October 18, 2013, 08:48:20 pm »
Mount your husky in a vice by the bar and start it up. Find out?
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Offline jmester

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Re: Stihl Chainsaw AV Design and Possible Boot Problems
« Reply #8 on: October 19, 2013, 12:49:10 pm »
No can do my vise and shop is in the basement of our house, wife won't like the fumes. Do you think all that vibe and motion is transferred to your hands.
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Offline Al Smith

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Re: Stihl Chainsaw AV Design and Possible Boot Problems
« Reply #9 on: October 19, 2013, 01:12:25 pm »
When I got the 038 Mag from  Rocky in  Fla it had all the av mounts torn out from rough handling plus the boot .How they ever kept from burning up that saw I'll never know .It was that way when Rocky got it .

Since I rebuilt and souped it up I've managed to tear out the top av mount twice plus two boots .It wasn't from rough housing it more from flexing under heavy load and bearing down on it .It has a lot more power under load than in stock form .I've since let up on it in a heavy cut .Slow learner . ;)

 

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