Husqvarna 3120xp ported inconsistent 4stroke rpm

[davidwyby]

Where would you start?

 

[jacob j.]

Does it still have the semi-fixed jet carb or did it get a converted carb?

 

[davidwyby]

Does it still have the semi-fixed jet carb or did it get a converted carb?

‘Justable

 

[Maintenance Chief]

Fuel filter.

 

[~WBF]

.. Air filter, choke function,muf screen, carb settings-- otherwise response to normality of all 3 settings,spark plug. Was it running a consistent 13ish before or is it climbing up to that? If so then i would be looking at fuel restriction, possible crap behind the needle or even sucking air at times. Maybe just tuck in your shirt tail,,lolz
Idle seems low. Maybe start with a bit more idle. It cools better and won't shake so much. May be getting to much on the low jet..for what ever reason??
if you throttle off a little after it hits 13 then will it go back to 13 right away?
It looks to shake-bad coming up from idea at times. I couldn't hear the vid but can get a pretty good idle by watching.

 

[huskyboy]

Who ported it?

 

[~WBF]

What's with the editing glitch with this site?? *idea..idle
it took 5 times for it to take but once you flick of the page it turns back to idle instead of idea. come to think about it a remember this happening a lot from before.

 

[~WBF]

Who has had problems with editing posts on this site before?

 

[davidwyby]

Who ported it?

Copsey

 

[davidwyby]

.. Air filter, choke function,muf screen, carb settings-- otherwise response to normality of all 3 settings,spark plug. Was it running a consistent 13ish before or is it climbing up to that? If so then i would be looking at fuel restriction, possible crap behind the needle or even sucking air at times. Maybe just tuck in your shirt tail,,lolz
Idle seems low. Maybe start with a bit more idle. It cools better and won't shake so much. May be getting to much on the low jet..for what ever reason??
if you throttle off a little after it hits 13 then will it go back to 13 right away?
It looks to shake-bad coming up from idea at times. I couldn't hear the vid but can get a pretty good idle by watching.

sometimes it will hold/4stroke at a lower rpm, sometimes a higher, and sometimes creep up.

 

[Lnk]

Either you have an intermittent air leak, or an intermittent fuel delivery problem. I would swap carbs with another known good one, or go through the fuel tank, vent, carb. The fact that it changes, and not based on how hot it gets makes me suspect fuel delivery. I may be wrong though, I don't know that saw at all.

Good luck.

 

[Mastermind]

I've chased that issue on a couple of 3120s. Once I wound up drilling the seat under the needle out a few thousandths. Not always an easy thing to fix. Is the saw hot? As in.....been making cuts?

 

[davidwyby]

I've chased that issue on a couple of 3120s. Once I wound up drilling the seat under the needle out a few thousandths. Not always an easy thing to fix. Is the saw hot? As in.....been making cuts?

Thanks for stopping by.
Yes, hot. I was alternating cuts (36”) and tuning and it was hot outside. I would get it where I thought it was good out of the wood and then it would be different in the wood. I finally held the trigger down longer than I felt like I should multiple times and found the inconsistency.
@Lnk i have a stock carb on a saw that runs but I have not tested in wood.

 

[Mastermind]

Thanks for stopping by.
Yes, hot. I was alternating cuts (36”) and tuning and it was hot outside. I would get it where I thought it was good out of the wood and then it would be different in the wood. I finally held the trigger down longer than I felt like I should multiple times and found the inconsistency.
@Lnk i have a stock carb on a saw that runs but I have not tested in wood.

It's not going lean enough to hurt it. But it also ain't quite right.

 

[davidwyby]

@Mastermind yeah, I ended up leaving it to where it couldn’t get too high rpm or too lean. It’s not hard to load it enough to pull it out of 4 stroke if it’s a little fat with a big bar in hard wood…troubleshooting it isn’t high on the priority list. I think I just got the 2139 sorted (again) and it’s number one right now. Then I need to test those used 61/266 coils and see about getting my $ back for what’s not up to snuff.

 

[Maintenance Chief]

Does the 3120 have the hole in the crank for oiling the pto bearing?

 

[Mastermind]

Does the 3120 have the hole in the crank for oiling the pto bearing?

Yes sir. And I'd fill that hole with epoxy on a well used saw.

 

[Maintenance Chief]

Yes sir. And I'd fill that hole with epoxy on a well used saw.

Ok, I saw a thread on that somewhere? But I figured it might apply here.

 

[jacob j.]

Ok, I saw a thread on that somewhere? But I figured it might apply here.

I think pretty much all of them do and they've caused me grief in the past. Some other members and I were discussing it and the consensus was that the
chainsaw and demolition saws have the same crank, all with that lubrication port.

 

[~WBF]

@Mastermind yeah, I ended up leaving it to where it couldn’t get too high rpm or too lean. It’s not hard to load it enough to pull it out of 4 stroke if it’s a little fat with a big bar in hard wood…troubleshooting it isn’t high on the priority list. I think I just got the 2139 sorted (again) and it’s number one right now. Then I need to test those used 61/266 coils and see about getting my $ back for what’s not up to snuff.

OK, is there a significant delay though when you load it up. As to say, does it clean up instant with not to much load? Normal. What does your plug and top of piston look like? Ever had way-high RPMs on the high where you reset the high and low?

See how it responds when the saw is just warm. Make saw the fins are clean and start cover has no plugs and passage is free and clear to air box. couldn't really tel if it was running a bit erratic on the idle with no volume.
I saw that dust crap you where cutting from the windy side. I'm surprised it didn't kill both. I would be wearing a dust mask if I had to cut much of that.
You did try it without the filter didn't you?