another Husqvarna 394xp project

dooly · October 16, 2010, 05:27:59 PM

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 · October 17, 2010, 07:54:23 PM

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 · October 17, 2010, 08:21:57 PM

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 · October 17, 2010, 09:19:32 PM

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 · October 18, 2010, 04:01:10 PM

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 · October 19, 2010, 12:48:42 PM

"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 · October 19, 2010, 01:35:39 PM

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 · October 19, 2010, 03:59:59 PM

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 · October 19, 2010, 04:33:34 PM

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 · October 19, 2010, 05:19:12 PM

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 · October 19, 2010, 06:01:04 PM

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 · October 19, 2010, 06:11:10 PM

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 · October 20, 2010, 10:30:30 AM

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 · October 20, 2010, 11:26:02 AM

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 · October 20, 2010, 01:12:55 PM

"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 · October 20, 2010, 02:53:53 PM

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 · October 20, 2010, 03:37:08 PM

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 · October 20, 2010, 05:49:18 PM

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 · October 20, 2010, 07:14:00 PM

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 · October 20, 2010, 08:13:42 PM

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 · October 20, 2010, 09:13:37 PM

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 · October 21, 2010, 01:33:35 AM

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 · October 21, 2010, 07:00:12 PM

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 · October 27, 2010, 07:26:54 PM

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 · October 28, 2010, 12:05:15 PM

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?