Husqvarna 3120 problems

[pdqdl]

I am seeking some recommendations as to how to proceed. Purchased in 1996, it has been running very well with no repairs or modifications. No high speed screw, no primer bulb present.

Problems: starts well, but often runs WAY fast after it warms up. It's not 100% of the time, but usually goes too fast (1/2 WOT with no load) once warmed up. It really runs nicely at full power, and still "hunts" at wide open. I'm thinking throttle plate not working right or throttle cable hanging up. All the threads I have read suggest an air leak as well.

It won't idle well when warm, and usually dies when turned on its side, unless you keep your finger on the throttle (unless it's racing too fast). That has always meant crankshaft seals are leaking to me, but I have recently read other info about running too rich on idle (something Ive never seen).

I obviously can rip the whole thing apart, and do a piece by piece reconstruction, but I'd rather not.

Recommendations? (No, I'm not interested in any high performance modifications.)

 

[lovetheoutdoors]

just box it up and send it to me

 

[Eric Modell]

It sounds like you have an air leak. Fix the saw before you seize the piston and cylinder.

 

[B_Turner]

Since you are not getting much response I thought I'd reply so you won't feel ignored.

To check for leaks around the carb, how about carefully spraying something like starter fluid near carb boot and gaskets while idling and see if idle speed changes.

Have you ever had the top cover off? Easy to accidentally pinch and thus damage the throttle cable on the 3120 when putting the top cover back.

Good luck and I would definitely find the probelm before I ran it much.

 

[FELLNORTH]

i would say when the saw is idling normally ( if you an achieve this ) use an unlit propane torche an introduce propane to all parts that could be sucking air. if the idle pick up it because you found the problem spot.
good luck and happy hunting

 

[Saw Dr.]

Sounds like crank seals to me. Definately an air leak. Crank seals are not the easiest to change, but a whole lot cheaper than a top end. If you run it like this, you WILL sieze it in very short order. Ya might want to pull the muffler and have a look at the piston. It might have already started to nuke.

 

[SkippyKtm]

Sounds like an air leak to me also. Here's the link to the Poorman's guide to Vacuum Testing:
http://www.arboristsite.com/showthread.php?t=42768&highlight=poor+mans
Its a very good guide, and doesn't cost much in tools, Its way cheaper than buying a top end!

 

[pdqdl]

An update !

We began taking it apart today. Findings:

1. Frayed throttle cable, this is almost certainly the runaway engine problem. It did not always return to "closed". parts ordered.
2. No evidence of other air leaks, throttle plate appears to be in good condition. Carburetor gaskets all good and tight.
3. The oiler cable is also frayed and out of adjustment; parts ordered.
4. We are concerned about the running poorly in different positions, engine crankcase seals ordered. We'll put them in whether they need it or not.

Does anyone have advice for how to replace the crankshaft seals? I have never done that to a husqy, and I don't have a flywheel puller. I imagine that I can get the flywheel off without the special puller, but is it possible to dig out the old seals and insert new ones, or is it necessary to break the saw all the way down and separate the crankcase?

That would be a bunch of work, and I no longer have the special tools to do a vacuum test when it is all put back together.

Any advice will be appreciated.

 

[pdqdl]

Sounds like an air leak to me also. Here's the link to the Poorman's guide to Vacuum Testing:
http://www.arboristsite.com/showthread.php?t=42768&highlight=poor+mans
Its a very good guide, and doesn't cost much in tools, Its way cheaper than buying a top end!

Thanks for the reference! You posted as I was typing.

 

[pdqdl]

...Have you had the top cover off? Easy to accidentally pinch and thus damage the throttle cable on the 3120 when putting the cover back.

...

You must know your 3120's pretty well. Yes, that had been pinched in the past by one of my previous mechanics. It was characteristic of his work, and I finally got rid of that headache.

But you're right, it could have been the problem.

 

[SkippyKtm]

As far as the flywheel puller, you can make your own if you have a welder or can braze. I made one for a Stihl- works Ok -it worked for 1 flywheel and then the threads(they are NPT-NOT metric) stripped(the flywheel threads were undamaged). So its basically good for only one use. Here's another link(this is for a Stihl puller I imagine that the Husky is similar):
http://www.arboristsite.com/showthread.php?t=22261