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Siezed 394XP teardown help needed **SOLVED**

Started by Dave Shepard, October 30, 2007, 06:25:29 PM

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Dave Shepard

I have decided to tackle the rebuild of my siezed 394XP. I took the muffler off and I can see very light scoring of the piston. I have tried to spin the flywheel to see if the piston would move at all, but no luck. How do I remove the jug without damaging it any further? I think the jug my be salvagable. I was quoted $600 to replace complete top end and crank seals. :o That is out of budget, (I can get a new 24" 660 for $900), but if I can get away with a new piston, gaskets and seals and do the work myself, I'll give it a try. Any advice or suggestions would be appreciated.

Whether or not I do this depends on what is involved, and the availability of parts. I was offered a very good deal by one of our members for a porting/rebuild job, but if I can get it running in stock form for now, I need to pursue that option. Thanks.


Dave
Wood-Mizer LT40HDD51-WR Wireless, Kubota L48, Honda Rincon 650, TJ208 G-S, and a 60"LogRite!

sawguy21

It sounds like the piston may not be the problem if there is only light scoring. Possibly a crank bearing has failed. Disconnect the choke and throttle linkage, remove the four cylinder hold down screws with a T-handle allen key and remove the cylinder if you can. If it is jammed you may need to stick a punch through the spark plug hole and break up the piston.
old age and treachery will always overcome youth and enthusiasm

Dave Shepard

Thanks, I didn't try too hard to turn it over, I didn't want to make it any worse. From the dirtbikes I've worked on, I think it is the piston, but I'll know more when I take it apart. I don't have a reason yet as to why the motor failed, but from talking to a few people, I have heard that this model Husky is prone to fuel line failure, leaning out the engine. I would at least like to find a cause, the saw is very low hours, and was properly maintained/proper fuel.


Dave
Wood-Mizer LT40HDD51-WR Wireless, Kubota L48, Honda Rincon 650, TJ208 G-S, and a 60"LogRite!

CALSAW

If you decide to rebuild it yourself  Bailey's should have the parts.
Lucas 827 w/ slabber

Dave Shepard

I pulled the jug off, and the piston slid right out. The bore has a little bit of discoloration from the aluminum, but most of it wiped off with my fingers. The piston is toast, so I think I can get away with a new piston and rings. Is running a cylinder hone very lightly through the jug ok? I still have to chase the gas lines to see if they are ok, still looking for a reason for the failure. Crank bearings seem ok at a glance. More at 11:00 o'clock, as they say on the news. :D


Dave
Wood-Mizer LT40HDD51-WR Wireless, Kubota L48, Honda Rincon 650, TJ208 G-S, and a 60"LogRite!

sawguy21

Just clean off any aluminum and check for scratches that catch a fingernail. Honing it will ruin the coating.
old age and treachery will always overcome youth and enthusiasm

ladylake

What was keeping it from turning before if the jug slid right off? Are you sure the bearing aren't binding up ?  Steve
Timberking B20  18000  hours +  Case75xt grapple + forks+8" snow bucket + dirt bucket   770 Oliver   Lots(too many) of chainsaws, Like the Echo saws and the Stihl and Husky     W5  Case loader   1  trailers  Wright sharpener     Suffolk  setter Volvo MCT125c skid loader

Dave Shepard

I don't know why it slid apart, probably the aluminum broke free when I started pulling on the jug. Sayguy, so the nickasil is applied after the final honing of the cylinder? That may be a problem. The bore doesn't seem to have any serious damage, but there is some aluminum stuck to it, not sure how I should clean it. The bearings feel fine, the crank turns freely now. CALSAW, you mentioned Baileys, do they stock parts not listed in the catalog? If I have to spend $450 on a new top end and gaskets etc., I may reconsider the Stihl, I now have a lead on 660's with bar and chain for $800. :o :o :o


Dave
Wood-Mizer LT40HDD51-WR Wireless, Kubota L48, Honda Rincon 650, TJ208 G-S, and a 60"LogRite!

CALSAW

Dave, Bailey's has a lot more than is listed in the catalog!
394 piston kits are on sale now for 29.95, that must be for aftermarket.
You can check online, but I would recomend calling them. They are great.

I have an '89 394, still running strong, with who knows how many 100's of hours on it.
I bought it used from a logging company in Washington, so I don't think it was babyed. :)
Lucas 827 w/ slabber

Dave Shepard

Wow, I woldn't have thought I could get this saw up and running that cheaply. I wish I had torn it apart sooner. Still the matter of the questionable jug though. :-\


Dave
Wood-Mizer LT40HDD51-WR Wireless, Kubota L48, Honda Rincon 650, TJ208 G-S, and a 60"LogRite!

ladylake

Dave  Muratic acid will eat the aluminum away with out harming the cylinder. Snowmobilers use it quite a bit. It's sold at hardware stores and lumber yards used for cleaning brick. Don't get it on anything else, maybe use a Q tip to apply.  Steve
Timberking B20  18000  hours +  Case75xt grapple + forks+8" snow bucket + dirt bucket   770 Oliver   Lots(too many) of chainsaws, Like the Echo saws and the Stihl and Husky     W5  Case loader   1  trailers  Wright sharpener     Suffolk  setter Volvo MCT125c skid loader

Dave Shepard

Thanks, I'll give that a try. I'm excited to think I can get my favorite saw back. Any way to check the crank seals? Or do I have to put it back together and do a compression test? Thanks.

Dave
Wood-Mizer LT40HDD51-WR Wireless, Kubota L48, Honda Rincon 650, TJ208 G-S, and a 60"LogRite!

sawguy21

Now that you have gone this far, why not replace them anyway. You don't want a bad seal to cause a second failure.
old age and treachery will always overcome youth and enthusiasm

Dave Shepard

I am guessing the hardest part of that is going to be getting the flywheel off, right? Any special tools needed? Thanks.


Dave
Wood-Mizer LT40HDD51-WR Wireless, Kubota L48, Honda Rincon 650, TJ208 G-S, and a 60"LogRite!

Kevin

Once the nut is removed you may need a set of pullers.

Dave Shepard

I've got lots of pullers, probably 200 pounds of them. (It's easier to quantify them in pounds than to try and count them, we've got lots.) :D


Dave
Wood-Mizer LT40HDD51-WR Wireless, Kubota L48, Honda Rincon 650, TJ208 G-S, and a 60"LogRite!

sawguy21

Remove the nut and washer then run the nut in until it is flush with the end of the crank. Put some pressure under the edge of the flywheel in line with the key with a screwdriver then give said crank a sharp , I said SHARP boy, smack with a hammer. The taper fit should come loose without wrecking anything.
old age and treachery will always overcome youth and enthusiasm

Dave Shepard

While I've got this thing apart, any suggestions on opening it up a little? You guys must have known this was the next step, right? :D I'd like to do something with the muffler, possible polish things up, if it isn't too involved. I have time, it gets dark real quick these days. :) I'm not trying to make a crazy saw, but I have heard that it will run cooler with a little work. Thanks.


Dave
Wood-Mizer LT40HDD51-WR Wireless, Kubota L48, Honda Rincon 650, TJ208 G-S, and a 60"LogRite!

leweee

Dave you need to talk to Ed Heard (EHP) one of our fellow members. ;D

EHP
just another beaver with a chainsaw &  it's never so bad that it couldn't get worse.

arojay

My 394 seized once.  It was about 3 years old and I had only used it for bucking up until a couple of weeks before the seize.  I had started to use it for felling and cutting stumps low in some bigger timber.  Well,  I made a cut and shut it down and when I tried to start again it had seized.  It was just about dark, so I put it in the truck and went home.  Took it in the shop and gave it a pull.  Round it goes.  Hmmm.  Next morning I started it outside the shop, seemed OK so in the truck and off to the bush.  Went to start it and it is seized.  Hmmm is a little milder than what I really said.  Back in the shop that night I start to take the jug off and find that the wrist pin is hanging out and hooked into a port and has gouged up the wall.  No sign of keepers in the jug, the muffler or anywhere.  I put it back together and took it into the dealer for their mechanic to look at because I figure it was a bit of a warranty case.  They balked a bit because I had started to tear it down but I made a bit of a case for the keepers to have been missing all along and ended up with about half of the rebuild cost returned to me from Husqvarna.   
440B skidder, JD350 dozer, Husqvarnas from 335 to 394. All spruced up

Dave Shepard

I took a picture of the jug, not sure you can really tell to much just from the picture though. There just appears to be some aluminum stuck to the bore, no scratches that you can feel.



We discussed honing the bore earlier, and it was decided it was a bad idea. I see Baileys has a half a page dedicated to cylinder hones for chainsaws, are those hones not as aggresive? Thanks.


Dave
Wood-Mizer LT40HDD51-WR Wireless, Kubota L48, Honda Rincon 650, TJ208 G-S, and a 60"LogRite!

ladylake

Dave I've always honed when putting in new rings and pistons, sure looks like your cylinder was honed in the first place as I think I can see the cross hones. Muratic acid should take the aluminum off, dab a little on and let it sit for a while, it eats it away (works really good on rust too). I'd take some really fine sandpaper and sand a little around the darker area. Can you put a picture of the top of the piston, should be able to tell if it was running lean from that. The top of the chamber looks pretty light to me. 
Timberking B20  18000  hours +  Case75xt grapple + forks+8" snow bucket + dirt bucket   770 Oliver   Lots(too many) of chainsaws, Like the Echo saws and the Stihl and Husky     W5  Case loader   1  trailers  Wright sharpener     Suffolk  setter Volvo MCT125c skid loader

Dave Shepard

Here is a shot of the piston. It looks a little blacker in person.




Dave
Wood-Mizer LT40HDD51-WR Wireless, Kubota L48, Honda Rincon 650, TJ208 G-S, and a 60"LogRite!

joe_indi

Dont hone it.
Use Muratic acid.Muratic acid is actually hydrochloric diluted to 25% strength.
I use hydrochloric acid as it is.Works faster.
Soak a cotton bud with the acid and keep rubbing it on the aluminum till it turns black in color.
Wash off the acid with water and use waterproof  silicon carbide paper (used in paint shops)to remove the aluminum.This is altogether a 5 minute job.
Dry the jug in the sun or top of any warm surface.
By the way, looking at the color of the side ports and deposits on the piston top in the images, I think you need to change  your brand of two stroke oil.

Joe

Dave Shepard

I use Stihl Premium mix oil, at 50:1, have been using it I first started running two stroke equipment, and that is what we always have used where I first started doing landscape work. Probably have run 75 different powertools on the stuff, and this is the first failure.


Dave
Wood-Mizer LT40HDD51-WR Wireless, Kubota L48, Honda Rincon 650, TJ208 G-S, and a 60"LogRite!

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