Husky 390 help

[Terrence Jefferson]

this is the exhaust. I didn't raise or lower either of these ports just widened tbem. I also pulled the piston this am when i took these and the skirt fully covers the intake port. I agree its a timing issue but im completely lost. This saw was toast and the piston crank and culinder are all new from husqvarna

 

[drf256]

Work looks OK. I’d make your ex roof more symmetric if it was me.

If you’re not freeporting, I doubt the porting is doing anything bad.

Another vote for timing here.

 

[drf256]

Yea. Your going to want those flames shooting back into the cylinder. With out them, you wont have any compression. Those flames are your compression escaping, that's how s 2 stroke works.

Amazing. Best answer material.

And don’t forget, it’s the atmospheric pressure that’s flowing through that engine, the piston is a passive bystander.

 

[beaglebriar]

View attachment 222434 View attachment 222435 View attachment 222436 this is the exhaust. I didn't raise or lower either of these ports just widened tbem. I also pulled the piston this am when i took these and the skirt fully covers the intake port. I agree its a timing issue but im completely lost. This saw was toast and the piston crank and culinder are all new from husqvarna

What other saws do you own? If you have a 372/365/2171/2172/2165 available you can swap the flywheel and coil over to the 390 for troubleshooting. As long as the ports are reasonably covered you probably didn't go too wide but baby steps would have been a better approach.

I would focus on getting the flywheel right as that's the most likely culprit. Followed by the coil as previously stated. What are your carb settings and is the carb in good working order? You basically have to go down the list...

 

[mdavlee]

The ports aren’t too wide. The cylinder extension is narrower than the skirt best I remember. I bet the flywheel turned when it was tightened

 

[RIDE-RED 350r]

Gotta go with ignition timing here. The symptom is classic for timing being off.

 

[Terrence Jefferson]

Ok could a coil cause this issue as well ? Im just asking but i will take both off the 372 i built last fall.

 

[mdavlee]

It could be the coil but I’d swap one part at a time to eliminate the real problem.

 

[Spladle160]

It's also very important to torque the flywheel nut properly. Service manual shows 35 Nm. I will torque the nut, back it off once and torque it again to ensure the tapers are seated.

Just my amateur 2 cents here as most of these guys are more experienced than I am. More important than properly torquing the flywheel is proper cleaning and fit. the 95% of what's stopping the flywheel from spinning on the crank is the friction between the flywheel and shaft. Yeah, the nut needs to be tight but a tight nut on a greasy mis-matched angle connection will just keep shearing keys.

I don't know how others feel about it but I have used some lapping compound to on the shaft and flywheel to make sure they mate cleanly then thoroughly cleaned and de-greased. No more slipping after that.

 

[Mastermind]

Yea. Your going to want those flames shooting back into the cylinder. With out them, you wont have any compression. Those flames are your compression escaping, that's how s 2 stroke works.

You're quickly becoming my new hero.

 

[huskihl]

You're quickly becoming my new hero.

He surely has it figured out

 

[Stump Shot]

Yea. Your going to want those flames shooting back into the cylinder. With out them, you wont have any compression. Those flames are your compression escaping, that's how s 2 stroke works.

@Termitebuffet is working on rerouting the exhaust to the carburetor for even more compression.
I think this is wonderful, finally a saw that can literally GFI.

 

[Termitebuffet]

@Termitebuffet is working on rerouting the exhaust to the carburetor for even more compression.
I think this is wonderful, finally a saw that can literally GFI.

This the bestest answer...troof too

Sent from a baked potato...

 

[ucm931]

Sounds like Robert Krogh and Stump (with Termitebuffet consulting) may have stumbled upon the operating theory for a matter/anti-matter 2 cycle chainsaw with EGR and and reverse.

 

[Terrence Jefferson]

Well i replaced the coil and the flywheel and it sparked rite up and ran well. I just need a throttle spring for the walbro carb and some other small things so i can run this thing. Thank you all for the help. I think i got all the flames contained now.