Husky 394XP New Project

[WolfMann]

Hey everyone, this is my latest project, a Husky 394XP. I'm new to these saws and stumbled upon it while helping a neighbor clean their barn, they said it's all mine if I'd like to get it running. Not sure how long it sat. I took it home and started looking it over, it's got spark and after setting the carb to a baseline tuning I was able to see an air fuel mix in cylinder. It still wouldn't start. I checked compression with an automotive compression gauge (what I've got) and saw a reading of about 60 psi, added a teaspoon of oil to cylinder and reading jumped to 90 psi. So I'm thinking piston rings, along with a new set of crank seals. But I haven't gotten very into the project yet and wanted to reach out here for some outside opinion. Maybe someone smarter than me knows something I've overlooked. Any help is appreciated, thanks guys.

 

[decableguy2000]

Pull the muffler and check the piston for signs of damage. That's the deal of the week for free. I'll triple your money. I would also check the flywheel key to make sure it isn't sheared and have the timing off. If the piston scored you need to pressure and vacuum test before you tear in to it to find out what caused it, if its scored.

 

[rupedoggy]

You need a new piston.

 

[cgraham1]

Hey everyone, this is my latest project, a Husky 394XP. I'm new to these saws and stumbled upon it while helping a neighbor clean their barn, they said it's all mine if I'd like to get it running. Not sure how long it sat. I took it home and started looking it over, it's got spark and after setting the carb to a baseline tuning I was able to see an air fuel mix in cylinder. It still wouldn't start. I checked compression with an automotive compression gauge (what I've got) and saw a reading of about 60 psi, added a teaspoon of oil to cylinder and reading jumped to 90 psi. So I'm thinking piston rings, along with a new set of crank seals. But I haven't gotten very into the project yet and wanted to reach out here for some outside opinion. Maybe someone smarter than me knows something I've overlooked. Any help is appreciated, thanks guys.View attachment 647696

How exactly did you test the compression? Does it feel like it has compression when you pull it over,or does it just spin freely? Pull the muffler off and inspect the piston through the exhaust port to check for scoring or a melted piston.

 

[WolfMann]

Thanks guys, I'll probably start getting into it tomorrow. Will be sure to pull muffler and check piston first. Cgraham, I threaded a compression guage into spark plug hole and cranked it over about 5 times. So is it just dirt and wear or is there some defect that causes piston trouble with these guys?

 

[WolfMann]

That's a great looking saw in your signature cgraham. Starting to give me ideas...

 

[cgraham1]

Thanks guys, I'll probably start getting into it tomorrow. Will be sure to pull muffler and check piston first. Cgraham, I threaded a compression guage into spark plug hole and cranked it over about 5 times. So is it just dirt and wear or is there some defect that causes piston trouble with these guys?

You’ve got to have a schrader valve in the end of your tester, where it screws into the cylinder, and you just keep pulling the cord until the gauge stops climbing.

There’s many threads discussing these saws if you do a quick search...

https://www.arboristsite.com/community/threads/husqvarna-394-low-compression.236212/

Apparently compression should be at least 150-170 psi. Usually an air leak or being straight gassed is what does them in. If there is scoring in the cylinder, often times it can be cleaned up, and a new piston installed.

 

[p61 western]

Hey everyone, this is my latest project, a Husky 394XP. I'm new to these saws and stumbled upon it while helping a neighbor clean their barn, they said it's all mine if I'd like to get it running. Not sure how long it sat. I took it home and started looking it over, it's got spark and after setting the carb to a baseline tuning I was able to see an air fuel mix in cylinder. It still wouldn't start. I checked compression with an automotive compression gauge (what I've got) and saw a reading of about 60 psi, added a teaspoon of oil to cylinder and reading jumped to 90 psi. So I'm thinking piston rings, along with a new set of crank seals. But I haven't gotten very into the project yet and wanted to reach out here for some outside opinion. Maybe someone smarter than me knows something I've overlooked. Any help is appreciated, thanks guys.View attachment 647696

Great score you got on that saw. Only thing I would add is make sure the decomp valve is out. You could also tape the throttle open as well.

 

[cgraham1]

Something else to look at...

check the intake block. i had a couple 394's do this and it was the same problem with all of them. the intake blocks crack and when cold the crack is closed tight but when at operating temperature the crack swells open. the 3 i had do it were cracked so there was an impulse leak when warm. would run fine as long as you kept it running but after shut off impulse wasn't strong enough to get them started again. cool down was the only way they would start again. i have had this problem on a few saw models with intake blocks actually. not just the 394. i got a pic. it appears to me that this crack is caused by overtightening the carb bolts. not saying it is for sure you issue but it's worth a look see.

View attachment 373326

 

[WolfMann]

Update:
So I took advantage of nice weather and got a little outdoor shop set up, started getting into saw, removed muffler as you all suggested, and sure enough there was piston scoring on exhaust side. Mostly minor but there's a couple deep scratches. Looks like I need to find a new piston. About to pause for some lunch, then I imagine I'll continue disassembly and cleaning. I wanted to ask about clutch and whether it's reverse-threaded? Other than that if anyone has any tips or advice for getting it apart, I'm always grateful. And here's a few more pictures for people like me who enjoy them.

 

[smokey7]

Please clean that saw around the jug and case area before you pull the jug. Also pressure test it before u pull the jug too. Once tou confirm a sealed case or a leak then you can pull the jug. I wasnt able to see in the pic if there was scoring or not. Very nice score and thank you for sharing your experience as you experience it. "Do it right and do it once."

 

[WolfMann]

Latest update:
That's good advice smokey, I've been cleaning as I go, didn't get pressure gauge hooked up, planned on replacing seals (but it would've helped with diagnoses). Saw is mostly apart, the piston rings were siezed in their groove on exhaust side, this is where the majority of scoring was too. I'm pointing with screwdriver in picture. I suspect this was the cause of low compression. Maybe carbon buildup created a hotspot, with a deposit eventually dropping in? Also unsure of darker score marks near top of piston, could that be improper oil mix? Spent some time moving rings around and almost freed them, but they both snapped in same spot. Flywheel key is in good shape, cableguy, good idea to check. Cylinder looks better than piston, still feels a little rough on finger nail, I'm wondering about a hone job. Here's a few more pictures.

 

[rupedoggy]

Do not hone your cylinder

 

[smokey7]

Get the transfer off with either the mastermind method or use some muratic acid from the hardware store. Even with acid some sanding is required. Im way jealous of your score even though its scored.

 

[WolfMann]

Thanks rupedog and smokey, I was just reading how it's a no go to hone over transfer. But I thought it was ok to hone after sanding transfer?
Is it best to avoid on aluminum/chrome plated cylinders?

 

[p61 western]

Thanks rupedog and smokey, I was just reading how it's a no go to hone over transfer. But I thought it was ok to hone after sanding transfer?
Is it best to avoid on aluminum/chrome plated cylinders?

Look up the Mastermind method before doing anything to the cylinder. A hone will ruin the cylinder.

 

[WolfMann]

I'll check it out, thanks guys.

 

[Stihl working hard]

https://www.arboristsite.com/community/threads/how-to-remove-aluminum-transfer-without-acid.248325/
Very interesting thread this one

 

[cgraham1]

I'll check it out, thanks guys.

Are you in Northern Ca?

 

[WolfMann]

Thanks stihl, great link.
Yeah cgraham, Trinity county, how about you?
Mastermind method looks brilliant, I'll pick up some emery cloth on the next trip to town.