Husky 3120 wont rev - stalls - did a carb clean up and no difference ??!

[chainsaw_louie]

Hi,

I have a 2-year-old Husqvarna 3120 chainsaw that I use for milling logs and occasionally cross cutting. Anyway, recently it stopped running properly.  (The warrantee period is over, but they never covered anything during the warrantee period anyway ...but that’s a different subject).

It will start on choke but then just run 20 beats or so and die, I can sometimes get it to rev up and stay revved up but as soon as I take my finger off the throttle it dies. Its like its starved for gas. After staring on choke and running 20 beats, it will start without choke but still just run 10 seconds at the most unless I can manage to get er revved up and keep it there, which is hard to do. 

Today I did the following:
1. Replaced the fuel filter
2. Blew out the air cleaner
3. Took off the carb removed the
- idle mix screw
- both cover plates and diaphragms
- the fuel metering valve and spring
4. blew it all out with compressed air, there was bits of rust/debris in the fuel screen etc. I hope that the compressed air cleaned it all  out.   When I saw all that debris in the filter screen etc I thought eureka! and congratulated myself for being so clever and all.

5. Re assembled the saw
6. Changed the gas for fresh mix

After all the above, I started it and there was No Change. It still will stutter and die and has lots of trouble revving up.  It wants to start but just keeps stalling.   I realized that I am not so clever but that junk in the carb couldn't have been helping so it was good to get it cleaned up even though it didnt fix the stalling problem.

Should I have soaked the carb in carb cleaner?

Somebody suggested a clogged screen in the exhaust port. 

I have heard that a leak in the crank seal can cause stalling but on a saw this new that would be pretty unlikely.

Any suggestions? 

Thanks.

Tim

[leweee]

Tim....check the impulse passageway ( sometimes the plastic block cracks from the heat of milling) Does this carb have a high speed jet or is it a fixed jet model?

[chainsaw_louie]

Thanks for the suggestion. 

This saw has just 2 adjusting screws on the carb a idle speed screw 'T' and a idle mix screw 'L' .  There is no  High Speed jet screw.  This is an 'EPA' carb and as I understand it cant really be adjusted. 

There is just one hose to the carb, its the fuel line.

I saw somewhere a mention of a clogged fuel tank vent - this sounds like its worth checking - I'm not sure if thats in the fuel cap or somewhere else. If its clogged it could limit the flow of fuel, no?

Tim

[woodbowl]

Tim,
   Sometimes the fuel line will suck air due to a crack in the line or around the fittings. Dirt dobber nest in the muffler even drives a mechanic crazy untill they check it.............last of course. Put in a new spark plug even if it already has one. Even a new plug can be bad. Can you squirt gas in the carb after it starts running and keep it running? That could cancell out a lot of other things.

[Kevin]

Check for an air leak around the carb mounting.

[YukonJon]

HI There

I had similar problems with 2 of my saws,  turned out to be fuel lines.  They must get soft & collapse inside or something. Worth a try.

Jon

[Paco]

sounds to me like the crank seal, a saw used for milling has more stress put on that than one just used for cross cutting. it is easy to check.  put some pre-mix gas in a spray bottle  and spray it on the seal with the saw bearly idling if it is leaking the idle will pick up.
               Paco

[chainsaw_louie]

Thanks.  I'll try the fuel spray trick  but  last night I opened it up and removed the carb and the intake boot but it looked like all was well.  Previously, I cleaned everything in there with compressed air and a rag...its spotless so I can see whats going on.  Unless I am missing something really small, there isn't a crack or break in the carb manifold boot.  The hole in the boot that carries the pulse is clear and ditto for the channel in the carb that carries the pulse to the diaphram. 

Other things I checked - screen in exhaust ...it was spotless.

I plan to check:
   
    "fuel tank vent"  but not sure what it is or where it is.  Any ideas?

     Fuel Lines but it looks like some trouble to get to where it passes through to the tank

     spark plug - just replace it in case

If that fails,  I'll try a carb kit just in case one of the diaphrams is bad.

If that fails, I'll try to find a good dealer and hand it over to them.

[chainsaw_louie]

Opps just re read your post Paco, you said CRANK SEAL  Sorry I misunderstood . Is that the seal where the crank shaft exits the case by the clutch?  Isn't there also a seal on the otherside by the flywheel that could leak too, right?

Tim

[woodbowl]

Tim, you can illiminate the vent question by unscrewing the cap a bit to allow equal pressure in the tank for the test. You can also illiminate the possible fuel supply problem by taking a plastic cola bottle, poking a small hole in the cap so the fuel squirts out in a fine stream. Take the air filter off and crank it like you have been doing. When it starts up, have someone squirt the fine stream of fuel mix directly into the carb with the throttle full open. If it continues to run untill you take away the stream, there is a fuel supply problem somewhere such as the diafram not pumping or an impulse channel. A bad crank seal is still a possibility.

[jokers]

......Fuel Lines but it looks like some trouble to get to where it passes through to the tank

It`s not as hard as it looks like to replace the fuel line. Unfortunately, the crack is either where the line passes into the tank or on the fuel nipple on the carb. It will be very hard to see unless you blow backward through the hose.

Russ

[Kevin]

A fuel line on a two year old saw?
They should last a little longer than that.

[jokers]

A fuel line on a two year old saw?
They should last a little longer than that.

Yeah Kevin, I agree. I have seen several that went south that quickly. Maybe it is something in our gas here. I noticed that Tim is also in NY.

Russ

[floyd]

are you running ethanol init? very hard on some rubber compounds

[jokers]

are you running ethanol init? very hard on some rubber compounds

Not deliberately Floyd, can`t guarantee that it doesn`t happen. Our gas is periodically oxygenated here in the winter.

Russ

[floyd]

I think the pumps must state there is ethanol in the fuel.

Bet your saw shop guy could relpace the fuel line for bout $15 in labor +parts.

You may have just gotten a lemon.

I have run huskys for a long time. goodsaws. I hope you figure this out.

[chainsaw_louie]

You guys age great, thanks for all the advice.

Today, I got a new spark plug and put that in....no change... still runs 10-20 beats and stalls.

Next, as "Woodbowl" suggested, I got the plastic squirt bottle with fuel mix in it.  By manually squirting a stream/drops into the carb I could keep the engine running, it would rev up no problem.  So I guess I have a fuel supply problem.

Am I right that this fuel problem could be caused by 1 of the 3 things:
   1.  Crack in fuel line   
   2.  Broken seal somewhere in the engine case
   3.  Bad diaphragm in the carburetor
   4. ??


The fuel line - I am not really sure how to access it to remove it and re-route it.  Anybody done this operation?

Broken seal - hmmm there must be a lot of possibilities.   The crank seems snug when I check it for side play at the clutch.  Would it be worth trying to spray/drip fuel mix on the crank seal by the clutch to see if it will suck fuel through a leak there?

The carb kit install I have done many times and that’s not a problem just bit of trouble to get the parts.

Thanks

Tim

[woodbowl]

You guys age great

  I know you got yer' g's and r's cornfuzzed, but we do age great as well.       If the fuel filter is in the bottem of the tank attached to the fuel line, you can hook it with a piece of wire, pull it off and pull your line out the other way. To put in a new line, do the reverse. If it's not the line or diafram kit, some small engine service centers have a carb shaker to dislodge particles during the soak.  Sometimes the new carb is the only way.

[chainsaw_louie]

Opps, on that , hope that bad spelling doesn't indicate my mechanical ability!

Okay, I think I can run a new fuel line using your method.

While I was looking for which panel to remove in or to replace the fuel line,  I  saw the tank breather under the shrouding....I want to clean that fella too.

One thing I DID NOT do was use carb cleaner.   I just used compressed air to blow out all the orifaces etc in the carb.   Does carb cleaner get stuff out that compressed air wont.

Tim

[twoodward15]

You've got to use carb cleaner.  Also, if there is a filter on the end of your fuel line (at the bottom of the tank) then you should remove and clean/replace it.  That could very possibly be your entire problem.  I'd probably start there and then if that doesn't work move on to the carb rebuild.  If you are going to take it apart or already have you should have either used new seals to reassemble or rebuil the carb.  A kit is gonna run you about $12 I'd guess.