another Husqvarna 394xp project

[dooly]

New here. Tried to first search the forum for my topic, but keep getting a message that the search daemon is broken.

Bought a used 394 xp. After 2 starts it froze up. Seller replaced the piston and rings. Used it for about 15 minutes and it froze up again. Exercised an infrequently used portion of my vocabulary. Finished the ripping job with my little Husqvarna 350. Seller remains in hiding.

Popped the cylinder and found the new rings broken and one of the cylinder side ports severely damaged. One chunk is jammed in the driveshaft and which explains why the engine wouldn't turn over completely. The rod and driveshaft, however, appear to be undamaged.

Need to split the crankcase to clean and inspect. I'm a first timer in that regard, and could use advice on the necessary tools. Don't mind laying out $65 or so for a Husqvarna crankcase splitter, but I'm a little hesitant to fork over $155 or so for a Husqvarna bearing puller. Are those tools absolutely necessary or are there acceptable alternatives for splitting the case and removing the driveshaft bearings?

Recommendations on where to buy the necessary tools, replacement cylinder head and gasket sets? (Hope that's okay to ask here.) Know of any place to by those ubiquitous hex head bolts in bulk? (Seem to be missing several.)

I'm also having trouble removing the carburetor and the carburetor mount. The shop manual doesn't really get into how that is done. Any insights others can provide on this project in general and my questions in specifics would be greatly appreciated.

Got a cabin to build and lots of free logs to rip for timber, so thanks in advance!

[dooly]

Saw is now broken down to point where the crankcase needs to be split. See lots of metal shavings in crankcase, but rod, crankshaft and bearings seem to be okay.

Plan to soak the halves in kerosene to clean things up and flush out all the shavings that I can. Is that adequate, or should I pop the bearings to be sure?

[Rocky_J]

Dave should be along shortly to comment. He has a 394 that he rebuilt from the crank up, including splitting the case. I wish I could be more help but I've never attempted to split a case on a chainsaw before.

[Dave Shepard]

I bought the puller as well. Money well spent. I didn't need any special bearing tools. If you've got junk in the bottom end, I'd be willing to bet the bearings are junk. The seals may also be bad, especially if you are having repeat failures. Cost for bearings was $12 and change each and seals $14, a complete gasket set from Bailey's was about $12, so for $64 you can freshen the bottom end. That's worth it on an $1100 saw. I have bought parts from both Bailey's (look for the Baileys/Lucas Mill tab on the left) and from my local Husky shop. A new top end was about $400 from another Husky shop in 2004, which is why mine sat for years. I was able to salvage my jug and put a new p and c, carb kit, fuel line, bearings and seals in it for about $150.

I think you need to find out why you are having failures. Lean run conditions are often the culprit in top end failures, whether from bad seals or fuel lines, or improperly adjusted carburetors. I suspect that the new p and c was not properly installed for you to have such a catastrophic failure in 15 minutes. Used jugs are hard to find, as that is the expensive bit everyone needs. Any chance you can post some pics of the inside of the jug? 395xp jugs will not work, unfortunately.

Here is the link to my thread on rebuilding my 394.

[dooly]

Thanks for the link, it was good reading. I'll post pictures of my project later this evening.

Is there any reason a large C clamp can't be used to split the case?

[dooly]

"I think you need to find out why you are having failures. Lean run conditions are often the culprit in top end failures, whether from bad seals or fuel lines, or improperly adjusted carburetors. I suspect that the new p and c was not properly installed for you to have such a catastrophic failure in 15 minutes. Used jugs are hard to find, as that is the expensive bit everyone needs. Any chance you can post some pics of the inside of the jug? 395xp jugs will not work, unfortunately."

The fuel line was split at the carburetor, but didn't seem to affect fuel supply. After the breakdown, the engine was very, very hot. I never ran the saw at more than about 3/4 throttle. (Sweet spot for ripping seemed to be about 2/3 throttle.) Breakdown occurred immediately after installing a new ripping chain. Fuel mixture was 33:1. Outside temp was 65^oF.

I've uploaded some pictures to my album. (Don't know how to do it inline in this message.)

Looking at the piston top, can anyone say anything about the fuel-air mixture I was running? Was it rich or lean?

[dooly]

Ahh, fun with posting inline images.

Ring groove damage in piston:



Too rich or too lean?



Chunks from the cylinder port:



Cylinder port damage, view 1:



Cylinder port damage, view 2:



Cylinder scouring that coincides with piston top damage. It's about 1" high and the width of the piston ring. Hard to see in this photo:

[Rocky_J]

Cracked fuel line (sucking air) and running the saw for extended periods under load at less than full throttle would probably be enough to kill it. Chainsaw carbs do not have a mid range jet, only a low speed jet and full throttle jet. Running at 2/3 throttle will cause the saw to run lean. A cracked fuel line will suck in air. Combine the improper throttle position with the cracked fuel line sucking air and you have an extreme lean condition.

If you need a new top end and the bottom end needs to be gone through, you might just consider replacing the saw.

[snowshoveler]

Thats not fuel damage in my opinion.
Thats mechanical interference,either the wrist pin clip came out and things went haywire fast or...its an aftermarket piston.
And it sure does look at an aftermarket piston.
Can you confirm the clips were in ,can you clean the top of the piston and post new pic.There will be some other markings near the direction arrow.
One other possible thing would be a bearing failure in the bottom end.
Thats pretty easy to check though.
Chris

[dooly]

The ring clips were intact when I opened the saw.

The second time I started the saw it seized up. Powerhead only, no bar and chain. There was a hole in the piston. The piston and crankshaft moved freely, but the crankshaft wouldn't turn all the way around. Probably piston parts stuck in a port. Sent it back to the seller, who replaced the piston only. I now suspect he never cracked the case to clear it of metal shavings, which likely played a part in the second failure.

Never knew that about not running the saw at full throttle. It seemed to be humming along in a sweet spot without laboring. The engine was very hot when it stopped running.

I definitely got ripped off, and the seller isn't doing much to make good on the sale. He has offered to give me a cylinder head, but it is scored. How badly I don't know, but I may take it and try to hone it.

[Rocky_J]

That's why I hate selling used stuff. Even if it's in good shape, an knowledgeable buyer can run it improperly and blow it up in 2 tanks of fuel, then accuse me of ripping him off. I rarely sell used saws and then only to people I know, just to avoid this kind of situation.

[snowshoveler]

Ill ask a few more questions if you dont mind,perhaps we can get to the bottom of this.
Might need a bit of Rocky's wisdom in this as well.
Im going to assume that the piston was installed correctly...arrow pointing to exhaust.
In your pic of the piston side view there appears to be a lot of casting flash,dont see much of this in an oem piston.
Im still leaning towards an aftermarket piston.
Could you perhaps give us a pic showing the face of the piston from the intake side.
Curious as to the position of the ring allignment pins.
I have a couple dead 394 pistons in my toolbox at work and would like to compare.
Chris   

[dooly]

The arrow was pointing towards the exhaust.

I'll post more pictures of the piston later this evening. It's likely that it was not an OEM piston, but I doubt that was the sole reason for the failure.

The seller sold this saw as "ready to work," the only caveat being that it should be run with a fuel mixture of 33:1 instead of 50:1 as recommended by the manufacturer.

I've already got $550 into this heap and will need to dump another $350 into money pit to get it running. I want to use it for milling 24 to 30 logs that vary from 12" to 28" in diameter and 10-foot to 14-foot in length. Species include redwood, tight-grained Douglas fir and Bishop pine. I've also got one uprooted 106-foot long redwood that is 54" at the base and 18" at small end.

Is that too much to ask of a rebuilt beat up old saw, or is it time to bite the bullet and buy new?

[snowshoveler]

It does indeed look like an aftermarket piston when i compare it to an OEM one.
Not saying that the aftermarket is bad,just have to make sure everything is right with it.
In your pic of the side of the piston it shows that the ring locating pinfor the top ring appears to be on the clutch side.The oem piston has this pin on the oposite side directly above the edge of the skirt.The lower ring has the pin on the clutch side above the edge of the skirt.
If the cylinder is symetrical from side to side I would say the pin mixup is no problem.
However if the cylinder is different side to side then you have a manufacture screwup and you should be after at least a new piston and cylinder.
As far as using it for milling...My used to me 394 has sawn on my jonsered mill well over 7500 feet of lumber.
Somewhere in my profile are pics of it.The inside of my saw is im very nice shape still.\
Chris   

[dooly]

"In your pic of the side of the piston it shows that the ring locating pinfor the top ring appears to be on the clutch side.The oem piston has this pin on the oposite side directly above the edge of the skirt.The lower ring has the pin on the clutch side above the edge of the skirt."

What is a ring locating pin?

[snowshoveler]

ring locating pin is in the groove that the ring fits in.
it keeps the ring from spinning all around the piston and catching in a port.
resulting in the above failure.
note we havent determined the actual cause of this particular failure.
Chris

[Jeff]

Dooly, have you maybe considered rather then dumping more money into the saw, to hire someone with a bandmill to saw your logs for you?

[dooly]

Yes, I have thought of hiring someone. It's not a huge job so'll I'll be paying a lot for mobilization and demobilization because of the remote location. The local guys are even more costly. Some want half the wood, which I need.

Since I'm not in a hurry, doing it myself is cheaper, even after taking a beating on my first big saw. Besides, look how much I'm learnifying from this forum!

Below is a photo of a jug the seller will give me:









It's been honed once already. Is that problem? Is there anyway to fix that blister?

[snowshoveler]

I get to see a lot of cylinders on a daily basis and i can say ive never seen one peel like that down on the bottom.
If was above the exhaust port i would scrap it.
However down there i would think its out of harms way.
Maybe Rocky will come in with his opinion,he is a little better that me with the high performance end of things.
If it was me I would clean up the bottom of the crankcase to make sure there are no more surprises and rebuild her.
Just give us a pic of the intake side of your new piston if you go aftermarket.
Chris

[Rocky_J]

You give me too much credit, my knowledge of deep internal workings is fairly rudimentary. I know just enough to sound like I know what I'm talking about!  :D

I can replace parts but know almost nothing about machining or welding. I did manage to install a heli-coil in a stripped out bolt hole once. 

[dooly]

Having trouble uploading more piston photos. I'll try later.

In the meantime, I'm having a heck of a time splitting that crankcase. Removed a total of 7 bolts, 1 long and 5 medium and 1 short. Was told I could hold the crankcase in my hand and whack the end of the shaft with a rubber hammer to split the case. Tried a slightly different method instead. Held the crankcase  securely in both hands, then whacked the crankshaft end hard against a wood block. Tried both the clutch side and the flywheel side several times. It won't budge. Filled crankcase with kerosene and letting it soak. (It's leaking out slowing so I may be making some headway.)

Hate to spend $84 plus shipping on a tool I'll only use once every 5 or 10 years.





















I think I'll give the blistered cylinder a go.

[sharkey]

You can use a piece of angle iron with a two jaw puller to split the case.  Drill holes in the angle iron for the bar studs and the crank.  Bolt the iron to the case with the bar nuts.  Use a heat gun or similar to heat the bearing races so that when they separate from the case the bearings stay on the crank.  You can use a torch if your not worried about the paint.  Your using the two jaw puller to push the crank out of the case. 

For reassembly, the crank with the bearings on it go in the freezer overnight.  The two case halves go in the oven on 300f for a half an hour before you want to put everything together.  Wear your mittens and work fast.  The heat expands the magnesium case so that the steel bearings will fall into place.  Use the long bolts to pull the two case halves together as they cool. 

You can also pull the crank seals and view the bearings to see what kind of condition they are in before you decide what you want to do.  If the bearings have alot of crud behind the seals I would replace the bearings and the seals. 

The cylinder with the small dimple should work fine. 

       

[dooly]

Thanks for the good advice, Sharkey!

I have a frozen Husqvarna 350 that my brother-in-law gave me when I bought his running 350. It's a great little saw. Now that I jumped in feet first attempting to fix my 394 I thought I might try fixing that frozen 350.

It looks like the crankcase splitter for the 350 differs from that for the 394. Does anyone know if the one for the 394 can be used for the 350? If so, I may bite the bullet and by the crankcase splitter for the 394.

[dooly]

Just picked up my splitter tool and successfully split the crankcase. It wasn't easy, even with that tool. Both sides suddenly popped off the crankcase. In both cases, the seals and bearing remained in the crankcase.

How do I remove the bearings without breaking the case halves?

[dooly]

Broke down and bought a crankcase splitter for my 394xp rebuild project. Even with that tool, splitting was far more difficult than I expected. Eventually, both halves did "pop" from the crankshaft.

But the bearings and seals are still in the crankcase halves. They're stuck pretty good, too. How do I remove them without breaking the crankcase?

There's a half moon key stuck in the crankshaft, too. Anything to worry about as I replace the bearings and seals?

[Jeff]

Dooly, I have merged the above post into this existing thread. It serves no advantage and makes no sense to split this off as a new topic.

[dooly]

Sorry about that Jeff. Thanks for making it right.

After a thorough cleaning with kerosene and soapy water, the crankcase halves are heating in the oven. In another 15 minutes they should be ready to smack the bearings out of them.

Looking at the crankshaft now. The small end of the rod can be wiggled back and forth ever so slightly. The big end has a little play along the axis of the pin connecting it to the crankshaft.

Is that to be expected, or do I need a new crankshaft too? I can post sketches to better illustrate the direction of play if necessary.

[dooly]

Heating the crankcase halves to knock the bearings out didn't work worth a hoot. Stunk the house up pretty good, though. A C-clamp and flat bar to press them out did the trick.

I've included a sketch of the play in the rod of my crankshaft. Good or bad?

Thanks in advance for any advice.

[dooly]

Cleaned up my cylinder with diluted muratic acid. Found another dimple higher up in the cylinder.

Is there any way to strip and restore the cylinder lining that is flaking off? How'd they put that on there in the first place?

This jug is in good structural condition. It's just the lining that's the problem. Suggestions?

[dooly]

How do you install the spring within the handle of the chain brake? (See attached photo.)

[sablatnic]

Your connection rod looks fine to me. I would use it. The spring is just pushed in past the holes for the locking pin. If it is like the older saws, it just sits above the locking pin, which sounds silly, but try it. Just make sure to orientate it like the one in the picture.

[dooly]

Got that chain brake handle working correctly. Shoved in the spring like you said and it works like a charm. I don't know how, but is does.

Just finished installing new bearings and seals, and putting the crankcase halves together. The crankshaft is really, really snug and it doesn't rotate easily. It's smooth but very stiff. Is that normal for new bearings?

[Dave Shepard]

No, you probably don't have the bearings seated in the case far enough. I had the same problem when I put mine together. I think I hit each end of the crank with a hard plastic mallet until it spun freely. Careful of the threads on the ends of the crank.

[dooly]

Okay, how to you reinstall those #*%$! rubber bumbers into the crankcase half without breaking them? I got the one in by the flywheel, but I've pretty much chewed up the one that goes near the chain oil tank.

Grrrr. I don't want to have to buy another special tool...

[Bandmill Bandit]

I haven't done a Husky chain saw but the blister in the bottom of the pot/jug indicates a chromed cylinder. Those cant be honed or re-used if there is any scoring checking blistering flaking etc.  at all. Also judging by the suggested price of that pot it would very likely be a chrome lined pot.

Guessing from your description of "your" second failure, the previous owner probably took it apart from what i would suspect was the third or forth failure from pealing chrome in the cylinder and tried to hone out those "flakeouts" in the wall to a point where your last failure ripped enough chrome out to cause the catastrophic failure you now have.

I can't be 100% positive but I can tell you from years of servicing the  Kawasaki snow mobile engines that Arctic Cat used to run, every thing you describe fits a chrome lining failure from an in experienced DIY guy that just doesn't know any better. Stick a honing tool in a chrome cylinder and you have pretty much guaranteed a catastrophic failure.  In most cases once you have a failure where pieces start to break out of the guts it is a "toss it and replace" exercise. That Chrome is so hard and shatters like tempered glass. It cuts its way into every thing and there is no way to get it completely and reliably clean.  

I will do a little checking to find out if husky still uses chromed pots. I know they do on some of their motor bikes. Will update when I get more info.

YES husky chain saws use DuraChrome cylinders! The best kind for performance and cooling but the absolute worst when they fail. It is pretty much a waste of time to rebuild an engine where there is significant damage to the chrome plating on the cylinder wall. It is rare that you will even be able to salvage the crank case.

I went back and looked at all the photos again. Every thing I see indicates Chrome failure. That pot he will give you is worthless. The blister is a result of an attempt to hone it. Check the case with a very strong magnifying glass or get some one to do a mag flux on it for you. That will show any ground in/buried chrome spots. If your lucky it will be salvage able but I have my doubts.

One other note. Chrome pots require chrome rings. Any thing else will last about 15 to 20 minutes max. They expand to much and break as a result.

[dooly]

Got a brand new OEM jug from ebay, which is now installed. Rebuild is almost complete. I have two remaining problems. 1)I don't recall where the 3" to 4" long black ground wire goes, and I can't tell from the parts manual or the shop manual. 2)Had to partially remove the gas tank and somehow managed to mess up the throttle cable at the trigger. Depressing the trigger doesn't open the throttle, but the cable end seems properly secured in the trigger itself.

Any help with either problem would be most appreciated.

[dooly]

Fixed the throttle cable. Secured the ground to a bolt for the plastic cover, one that anchors into the magnesium crankcase.

Pulled the starter rope several times to verify she turned over smoothly, which she did.

Gassed it up and tried to start her. Fired once or twice and stalled. Tried again. Fired once or twice and stalled. Tried a third time, same thing. Upon the fourth try, the starter rope turned, but the piston didn't move up and down.

I think I broke the connecting rod. Dang! This saw is jinxed!

[snowshoveler]

You cut flywheel key...pretty common mistake.
open it up and have a look.
Chris

[dooly]

You were absolutely right, the woodruff key was sheared off. Phew!

Flywheel and starter cover are back. Almost done, but not nearly quite. Read somewhere (perhaps here) that I should make sure the carburetor is set the the "break in" settings. Off now to figure what those are, unless someone here would like to share.

This forum has been an immense help in this rebuild project!

[Dave Shepard]

I don't know what break in settings are. I set mine to the factory 12,500 with a tachometer. It was running pretty rich. I should really retune it now, as it was four stroking at I think 13,000.

[dooly]

Whoo-hoo!

Fired up just fine after backing off each setting screw an 1/8th turn in the rich direction. Will fine tune settings after reinstalling the bar and chain.

Now all I need is a hockey mask.

Thanks everybody!