DIR Return Create A Forum - Home
---------------------------------------------------------
Chainsaw Repair
HTML https://chainsawrepair.createaforum.com
---------------------------------------------------------
*****************************************************
DIR Return to: Husqvarna
*****************************************************
#Post#: 55627--------------------------------------------------
older 394xp runs well, lacks power
DIR By: burl
Date: March 17, 2015, 9:53 am
---------------------------------------------------------
I have a late 90's Husqvarna 394xp that starts great and runs
well, but is lacking cutting power - somewhat less than my much
newer 372xp with the same bar length - 24". It produced 140 psi
with a compression test. Just looking into the cylinder from the
spark plug hole, it looks to me like it has light scoring. I'm
not a good gauge of scoring, but that's what the guy at the
local repair shop said when he took a quick look at it. I have
tuned the carburetor with a tachometer to the best of my
ability. Other factors that I should be looking at? Crank shaft
seal? New cylinder? Or just rings? Carburetor? Anything else?
Thanks, Brian
#Post#: 55628--------------------------------------------------
Re: older 394xp runs well, lacks power
DIR By: aclarke
Date: March 17, 2015, 11:02 am
---------------------------------------------------------
Pull it down and inspect it. Probably be able to cleanup the
cylinder scoring if it's not bad and replace piston and rings.
Vacuum/pressure test the crankshaft seals or just replace them
while the saw is apart. If it wasn't straight gassed, it likely
has an air leak so that needs to be sorted out before
reassembly. Adam
#Post#: 55692--------------------------------------------------
Re: older 394xp runs well, lacks power
DIR By: wisecobandit
Date: March 18, 2015, 4:02 pm
---------------------------------------------------------
Be sure to check the plastic inlet manifold for cracks
especially if its the white coloured 1 which can cause airleaks
and mess with the impulse feed. It's a common fault with them.
#Post#: 55715--------------------------------------------------
Re: older 394xp runs well, lacks power
DIR By: srcarr52
Date: March 19, 2015, 9:30 am
---------------------------------------------------------
--- Quote from: wisecobandit link ---
>
> Be sure to check the plastic inlet manifold for cracks
especially if its the white coloured 1 which can cause airleaks
and mess with the impulse feed. It's a common fault with them.
>
--- End Quote ---
Good call, I've had one crack on a friends saw and he didn't
catch it in time before he locked it up.
#Post#: 55718--------------------------------------------------
Re: older 394xp runs well, lacks power
DIR By: burl
Date: March 19, 2015, 11:01 am
---------------------------------------------------------
Thanks a bunch guys. I'm gonna go ahead and tear into it, test
the crank seals, and check the cylinder when I get a chance -
probably not for a couple weeks. Good one on checking for
cracking in the intake manifold too - I doubt I would have
caught that. Please throw any other thoughts my way in the mean
time. Thanks!
#Post#: 55738--------------------------------------------------
Re: older 394xp runs well, lacks power
DIR By: adam32
Date: March 19, 2015, 1:56 pm
---------------------------------------------------------
--- Quote from: burl link ---
>
> Thanks a bunch guys. I'm gonna go ahead and tear into it, test
the crank seals, and check the cylinder when I get a chance -
probably not for a couple weeks. Good one on checking for
cracking in the intake manifold too - I doubt I would have
caught that. Please throw any other thoughts my way in the mean
time. Thanks!
>
--- End Quote ---
Port it ;)
#Post#: 56220--------------------------------------------------
Re: older 394xp runs well, lacks power
DIR By: wisecobandit
Date: March 29, 2015, 4:00 pm
---------------------------------------------------------
I change crankshaft seals on most saws as a matter of course for
how much they financially are if theres a thought in my head of
a possible air leak. If your stripping the saw down to that
point it only takes a few minutes to stick new ones in.
Ive seen more 394's fail a pressure test on the inlet manifold
tho especially the earlier white ones (later are black) You have
to remember plastic/nylon being bolted to a hot cylinder isn't
the best idea and now with a bit of age behind them its almost
inevitable they will crack at some stage.
#Post#: 56489--------------------------------------------------
Re: older 394xp runs well, lacks power
DIR By: burl
Date: April 4, 2015, 2:54 pm
---------------------------------------------------------
Here are some photos of the piston from the muffler side of
things. Any thoughts on the scoring? Muffler has small hole
rusted through one corner, the outside/front face is a little
dented, and the screen in the exhaust port is open on one side,
but it otherwise seems functional. The white plastic intake does
not seem to be cracked. I'll pull to check the underside.
Thinking about getting a vacuum/pressure tester for carb., crank
seals, etc. What do people recommend? I've been looking at the
Mityvac 8500.
-Thanks
#Post#: 56502--------------------------------------------------
Re: older 394xp runs well, lacks power
DIR By: Eccentric
Date: April 4, 2015, 5:24 pm
---------------------------------------------------------
Looks like there's transfer from the piston to the cylinder. It
got hot/lean at some point. Better tear it down and deal with
it right. As to why it got lean.......................could be
seals. Could be an air leak elsewhere. Could also have been
tuned too lean....
#Post#: 57654--------------------------------------------------
Re: older 394xp runs well, lacks power
DIR By: alsled
Date: May 2, 2015, 8:26 pm
---------------------------------------------------------
Muffler screen plugged?
*****************************************************
Page 1 of 1