Husqvarna 3120xp ported inconsistent 4stroke rpm

[Canadian farm boy]

Change the fuel filter and check your fuel line. Fuel line could be soft and collapsing or pinched/kinked or have a pin hole in it.

 

[davidwyby]

Fuel line feels ever so slightly softer than the new echo line in my 395. The filter looked ok but I changed it.


Would someone elaborate on the oil lube port in the crank and fill me in?

 

[redline4]

Fuel line feels ever so slightly softer than the new echo line in my 395. The filter looked ok but I changed it.


Would someone elaborate on the oil lube port in the crank and fill me in?

Look at the clutch side end of the crank.
It will have an open hole in the end.

 

[davidwyby]

Look at the clutch side end of the crank.
It will have an open hole in the end.

Yeah most saws do I think…but what is the problem with it and why are we plugging it?

 

[jacob j.]

Yeah most saws do I think…but what is the problem with it and why are we plugging it?

I think the theory was that excess oil from the crankcase would travel down the opening (in the center of the PTO side crank throw) and then come
out that opening where the clutch drum bearing is to keep that lubed. However, a lot of the time it presents an air leak in the chainsaws.

I know on three 3120s I've built, I've had to plug it.

 

[davidwyby]

That has to be about the dumbest engineering I’ve heard of. I could see that being an intermittent air leak.


@Woodslasher didn’t you have some weird air leak on yours?

 

[Woodslasher]

That has to be about the dumbest engineering I’ve heard of. I could see that being an intermittent air leak.


@Woodslasher didn’t you have some weird air leak on yours?

Yep, it was 3 frickin’ vent plug thingies built in to the case behind the oiler.

 

[Mastermind]

Look at the clutch side end of the crank.
It will have an open hole in the end.

Not on the end of the 3120 Ed. It comes out off the center of the crankshaft inside the case, and ends at the clutch drum bearing.

 

[redline4]

Not on the end of the 3120 Ed. It comes out off the center of the crankshaft inside the case, and ends at the clutch drum bearing.

Ahhh, OK.
Thanks for the clarification and yeah, now that I actually think about it, how would the hollow grease end cause an air leak...
Dum chit..

 

[qurotro]

The hole on the drum bearing is a cheap out thing for Husky I think. If you have a 371K saw, that crank has this type of hole to the crank case but no hole on chainsaw cranks. They just made 3120 chainsaws using 3120K's cranks.
I have a 371K converted to chainsaw with that hole in the crank, it run just fine as a chainsaw.

 

[davidwyby]

Mike has a k starter but no idea what the saw started life as

 

[davidwyby]

Hole in clutch bearing area goes to outside for greasing, not to inside of case.

 

[qurotro]

Hole in clutch bearing area goes to outside for greasing, not to inside of case.

No. 3120 is different from the design of 395. The hole in the clutch bearing is to the inside. As well as the 371K.

 

[drf256]

How’s the tank vent? Air filter?

Sounds fuel related. I personally can’t see how a small air leak through a poorly engineered crankshaft weep hole would cause a high rpm issue. Should be able to tune it out. With a wide open throttle blade a tiny air leak shouldn’t pose a problem. A massive one that pulls a rip open in a boot or seal would, but there is less vacuum in the case when the butterfly is wide open.

Could also be a heat thing changing tune. Seems to hold same rpm for a few seconds and then jump. Most ported saws will jump in rpm when hot, part of why I like AT saws.

If you fatten it up more, will it hold the lower rpm steadily?

 

[Moparmyway]

If you fatten it up more, will it hold the lower rpm steadily?

Nailed it

 

[davidwyby]

No. 3120 is different from the design of 395. The hole in the clutch bearing is to the inside. As well as the 371K.

I checked.

 

[qurotro]

I checked.

Hm... Funny thing is I have 2 2012 395 and the hole is to the cage bearing. The 2011 3120's hole to the inside. And my avatar 288 is the same as 395.

 

[davidwyby]

Hm... Funny thing is I have 2 2012 395 and the hole is to the cage bearing. The 2011 3120's hole to the inside. And my avatar 288 is the same as 395.

I didn’t think to check my other 3120

@Armbru84

 

[davidwyby]

I idled it and gave it the spray leak test today. Didn’t find any leaks or loose bolts. I didn’t fool with the H as the saw is godawful loud and I don’t want my neighbors to hate me. Also, Need to put clutch bar and chain on and put it in wood to test/tune properly warmed up.

 

[davidwyby]

Finally used it again a year later. Had to chase the tune. Gonna order a carb kit and look into that.