Stihl 034AV strange problem

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hardhat

hardhat

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Took carb off. Metering lever was quite high above diaphragm floor. Obviously enough to prevent needle from closing completely. Bent it down flush with floor of carb and checked for range of motion. Saw runs like new now. Wish I would've checked this first, but now have given the old girl all kinds of TLC and she runs great.
 
Brent Nowell

Brent Nowell

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Everyone seems to be pointing to the metering area of the carb and I have to agree.
Sometimes when you get a new diaphragm and compare it to the old, the riveted plate that keeps the diaphragm uniform is higher or shorter than the stock one. In essence the lever height has to be adjusted to accommodate for this.
also sometimes, spring tension on new springs compared to old are different, some have more coils some have less. Pop off pressure will tell you what is what.
Your symptoms of turning your saw on the side and stalling indicate , to me at least, that the metering lever is allowing too much fuel to come through for the give. atmospheric pressure behind the diaphragm. Either a spring issue and or lever height issue.

*edit*damn 8 minutes too late to the party ...
 
Vintage Engine Repairs
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Pressure test the fuel inlet on the carb with your Mity-vac. It should hold 7-10PSI indefinitely. If it doesn't (and I suspect that it worn't) you will have found your problem. If you are using an OEM carb kit you can usually reuse the old metering lever to save having to readjust the new one. However, I always check them anyway.

worth noting for the OP, new needles don’t always hold pressure and sometimes need a little oil 2 fuel through it so don’t worry if new needles pop off the seat and don’t hold pressure . Obviously I wasn’t chasing my tail with this happening, oh no of course not!

also metering springs aren’t always standard length if someone stretches them. When adding new levers to old springs or vice versa worth still checking them with a gauge. Again, happened to me :)
 
Brent Nowell

Brent Nowell

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worth noting for the OP, new needles don’t always hold pressure and sometimes need a little oil 2 fuel through it so don’t worry if new needles pop off the seat and don’t hold pressure . Obviously I wasn’t chasing my tail with this happening, oh no of course not!

also metering springs aren’t always standard length if someone stretches them. When adding new levers to old springs or vice versa worth still checking them with a gauge. Again, happened to me :)
You should always test it with fuel in the carb period.
 
hardhat

hardhat

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oops just seen it’s all good! Hey what is that saw bar for?!?!

That is a bow bar. Wonderful for cutting logs laying on ground. Don't have to bend over and not constantly getting bar in the dirt. I use if for cutting up small (<12") logs that are laying on the ground. Also the bow doesn't pinch nearly as bad a a bar. You can kind of rock it back and forth a little if it starts to pinch and finish your cut. Next tree I cut, I'll get some videos up.
 
Vintage Engine Repairs
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Messages
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Wow that would be awesome to see thanks!
That is a bow bar. Wonderful for cutting logs laying on ground. Don't have to bend over and not constantly getting bar in the dirt. I use if for cutting up small (<12") logs that are laying on the ground. Also the bow doesn't pinch nearly as bad a a bar. You can kind of rock it back and forth a little if it starts to pinch and finish your cut. Next tree I cut, I'll get some videos up.
 

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