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Husqvarna 2100 idle woes

M2theB

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Helicoil's been installed, saw was re-assembled, and now the low end tune wanders more than a city driver on a backwoods road. I'm gonna p/v test the saw to confirm it but I'm suspecting one or both crank seals are bad.

See if you can find the manual.
If you do end up replacing the seals and test again for p/v , i remember OEM listed an allowable leakage rate of like 1.2 psi/min.
If you can confirm that, don’t let perfection be the nemesis of good.
 

Woodslasher

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Checked p/v, it lost ~1lb of pressure in 1 minute with a starting psi of 15 and it lost ~1somethingorother of vacuum in 1 minute with a starting vacuum of 15somethingorothers. Is that acceptable or not?
 

Woodslasher

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According to the book I should be within specs, correct? I was losing roughly .5psi of vac per minute and 1psi of pressure per minute so I am within the allowable spectrum. That doesn't explain the wandering idle, though. My only two thoughts are the low speed check valve could be intermittently failing or I'm screwing up when I'm trying to tune it.
Screen Shot 2021-08-18 at 8.15.27 PM.png
 

huskihl

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According to the book I should be within specs, correct? I was losing roughly .5psi of vac per minute and 1psi of pressure per minute so I am within the allowable spectrum. That doesn't explain the wandering idle, though. My only two thoughts are the low speed check valve could be intermittently failing or I'm screwing up when I'm trying to tune it.
View attachment 306070
That small of a leak won’t be noticeable in how the saw runs in my experience. I’ve never actually timed it to see how quickly pressure or vacuum falls off. Usually the needle either stays or it doesn’t. Most leaks that are bad enough to make the saw run poorly won’t hold 5 pounds of vacuum or pressure for more than 10 seconds or so.
 

Woodslasher

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That small of a leak won’t be noticeable in how the saw runs in my experience. I’ve never actually timed it to see how quickly pressure or vacuum falls off. Usually the needle either stays or it doesn’t. Most leaks that are bad enough to make the saw run poorly won’t hold 5 pounds of vacuum or pressure for more than 10 seconds or so.
In that case, what are your thoughts on the saw's wandering idle?
 

huskihl

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In that case, what are your thoughts on the saw's wandering idle?
I’ve actually never worked on a 2100, so I’m not that familiar with the model. But in every other 2 series with an issue, for me it’s almost always the gaskets between the carburetor, block, and cylinder
 

Woodslasher

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I’ve actually never worked on a 2100, so I’m not that familiar with the model. But in every other 2 series with an issue, for me it’s almost always the gaskets between the carburetor, block, and cylinder
You've never worked on a 2100!? Well damn, I'm stunned. Anyhow, the block to cylinder joint was tested, so the carb to block joint is the only possible leak left, I guess. I'll keep poking at stuff and update y'all if I find anything.
 

huskihl

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In that case, what are your thoughts on the saw's wandering idle?
I didn’t go back and read through the thread again so I may have missed it, but I can almost guarantee that if you reuse the gaskets and don’t get them in the same orientation as they were originally, it won’t seal. It’s probably obvious on the cylinder side which way the impulse hole needs to line up, but the carburetor gasket can usually be flipped if it has an impulse hole on each side.
 

Stump Shot

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According to the book I should be within specs, correct? I was losing roughly .5psi of vac per minute and 1psi of pressure per minute so I am within the allowable spectrum. That doesn't explain the wandering idle, though. My only two thoughts are the low speed check valve could be intermittently failing or I'm screwing up when I'm trying to tune it.
View attachment 306070

Try rolling the engine over to see if the leak gets better/worse or stays the course.
Leak can be different once the engine is warmed up as well, generally not in a good way either.
If it's leaking now in spec, how much run time does it have before it's out of spec?
As far as your problem goes, check for a leaky/worn throttle shaft/bore.
 

Stump Shot

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I’ve actually never worked on a 2100, so I’m not that familiar with the model. But in every other 2 series with an issue, for me it’s almost always the gaskets between the carburetor, block, and cylinder

Quite normal to have a cracked intake block on a saw of this vintage.
 

thedude74

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I see eBay and Amazon have a Chinese Tillotson HS136. Complete carbs for about $15......or you could just send me the piston and cylinder instead :D
 

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Stump Shot

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The block was included in the test, it checked out as ok.

It starts acting screwy within a minute or so.

Tank venting slow or seals letting go, ignition warming up and getting skittery are some things that change with time ran.
 

Woodslasher

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Tank venting slow or seals letting go, ignition warming up and getting skittery are some things that change with time ran.
Tank vent could be possible, although post-carb work it has gotten way worse, I'll have to twist the crank while I'm testing it later and I think this ignition is ok because it'll fire right up immediately after it dies (read: while it's still "hot").
 
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