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Chainsaw doesn't like air

Started by MonsterMash, March 04, 2016, 01:29:23 PM

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MonsterMash

Hey guys,
Thanks for letting me join your forum.  I heat my home with firewood and cut about 8-10 ricks per year. I also live on about 155 acres of mostly hardwoods, and find weekly uses for my saw.  I have a Husky 455 Rancher that has served me well for about 9 years.  After spending about an hour cutting two fallen oaks, I shut it down, then started it back up 5 minutes later to cut the stump off lower.  But  all of the sudden it did not have any power and would bog down and die at full throttle.  Started it back, good up to 2/3 throttle, bog down and die.  After thoroughly cleaning it, new gas, new air filter same story.  Here's the kicker, if I remove the air filter and place my hand over the carb to seal it off, runs like a champ.  This is consistent: no filter or new filter, bogs at 2/3 throttle.  Hand over carb air intake, runs great.  I don't know if you all have tried to cut wood while holding your hand over the carb, but its not easy. ;D I know this is probably something simple, but I don't know how to cure it.  I am a pretty mechanical guy, do most of my own car repairs, but carbs make me nervous, especially when I know I can ruin the engine pretty quick with the wrong setting.  Any thoughts?  Thanks, Erik

Jiles

My guess would be restricted carburetor. Give it a good cleaning and adjust close to what it has been for years.
If that's not it, check for air leak at seals or intake.
Satisfy needs before desires

limbwood


NCFarmboy

Lots & Lots of Saws

MonsterMash

Thanks guys. I did put a new fuel filter on it.  Just can't understand why it runs great when I restrict the air.  Maybe an air leak somewhere else?  Saw is in great shape otherwise, and if started this suddenly.  I will dig into the carb,  check for degraded lines. Thanks.

dougand3

It runs better on partial choke because the fuel delivered from the carb is not enough for the current amount of air. When you restrict air, you're getting back to the proper Fuel-Air ratio. It could be extra air from a cracked fuel line or reduced fuel delivery due to dirty carb or stiff diaphragms in carb. If it's 9 years old - I'd replace all fuel lines, purge bulb, carb to intake gasket, clean carb and put a kit in it (or new carb).
Husky: 372xt, 272xp, 61, 55 (x3)...Poulan: 315, 4218 (x3), 2375, 2150, 2055, 2000 (x3)...Stihl 011AVT...Homelite XL...Saws come in broken, get fixed or parted, find new homes

TimRB

I experienced those same symptoms--turned out to be clogged muffler baffles.  Take your muffler apart and burn off any oil or crud with a propane torch.

This problem so confounded me that I gave up and took the saw in to a repair place where the mechanic found the problem in nothing flat.

Edit:  Before giving up, I also did all the things suggested so far.

Tim

MonsterMash

Thanks guys.  I have taken the muffler of and cleaned,  was worried about dirt daubers.  I will get into that carb this week, and replace those lines.

XP_Slinger

Good advice on checkin the muffler.  If that's not the problem I would be hunting for an air leak....intake, base gasket, crank seals etc
346XP/NE
357XP...ported by MeDremel
372XP/XT...ported by A. Burr
Homelite (Solo) 340

I'd rather be in the woods than on this computer.

AdkStihl

If youre cutting of the air with your hand @ the intake............Its pulling air from somewhere else.
My guess is the impulse hose.
J.Miller Photography

MonsterMash

Guys, thanks for all your replies. I am taking my kids through Hunter Safety right now and have not had any time to mess with it.  My thoughts from the beginning that it was sucking air from somewhere else. 

MikeAM

Sounds like an air leak to me. A vacuum test should be in order. Figure out if its coming from the seals or impulse line. Something that sudden is probably the impulse line like some have said.    503 40 06-10 should fix you up.

Weekend_Sawyer

Did you find the air leak?

Does your Husky have the primer bulb?
If it does look to see if it's cracked. That'll do it.

Jon
Imagine, Me a Tree Farmer.
Jon, Appalachian American Wannabe.

DelawhereJoe

Have you done a rope hold test to check on compression just make sure the decompression valve isn't pushed .  It does sound like the carb is gummed up to me.
WD-40, DUCT TAPE, 024, 026, 362c-m, 041, homelite xl, JD 2510

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