Husquvarna 390 xp pto side bearing failures.

[Dieselshawn]

I just recently went into a small engines repair shop and the owner is a good friend of mine. We discuss many things about chainsaws and any other engines.

Today, he showed me a torn down husquvarnia 390 xp saw and pointed to the missing bearing cage for the pto crank bearing. Saw is used for professional logging.

He said they come with plastic cages and it was completely missing.

He's got another 390 xp on the floor as well. Same problem. Only thing is that both have been ported by different people but same problem. Only the transfer ports have been worked on to smooth out flow. Other ports still stock and the muffler modded a bit. Rpms have been raised a little.

He doesn't see this on factory 390 saws yet.

He asked me if it was lack of oil or poor oil or wrong oil something causing it to fail.

It runs on amsoil 2 stroke with a 50:1 mix ratio. The piston crown has carbon buildup and the skirt looks good. We figure its getting enough oil and its synthetic.

I told him that one logical thinking would be because its ported and turned up a bit, the guy can cut more wood and putting more load on the pto bearing causing it to run hotter and wearing the plastic out faster.

We're thinking of not buying original 390 bearings and get matching bearings from a bearing store with steel cages instead.

Does anyone know why these bearings fail and if porting jobs have anything to do with them or is it the oil or.....?

Is it only the 390xp that have them?

What could help make these 390's more reliable and keep their mild porting work?

In skidoo snowmobiles, plastic bearing cages have a bad reputation and skidoo stopped using them.

It never occurred to me that chainsaws would have them too.

 

[duramax99]

The PTO bearing is a husky only bearing. It's wider and has the crank seal as part of it. I see many more big end con rod bearing failures than I do PTO bearings. Possibly running too much chain tension?

 

[blsnelling]

It's recommended by some that know, to run 32:1 in the 390XP, as well as the 372XP, and perhaps others. I personally run 32:1 in all of my saws, but some saws seem to benefit from it more than others.

 

[Dieselshawn]

Duramax99: I'll have to check with the guy on chain tension.

Blsnelling: I'll tell him to tell the guy to run 32:1 once the saw is rebuilt.

 

[Andyshine77]

A well known saw builder told me running 32:1 almost completely eliminated bearing issues with the 372 and 385/390. Make sure the saw has plenty of fuel to keep the rpm's down a bit. This is especially important if they're doing a lot of light load limb work, that's really hard on bigger saws.

 

[mdavlee]

Yeah usually it's the big end that let's go in the 390 from added rpms. I was told by someone out west to keep the rpms on 390s below 13.5k with 32:1 and they'll live a long life.

 

[Dieselshawn]

Are the 372/385/390 good saws at all? Just some bearing issues and that's it?

 

[Eccentric]

Are the 372/385/390 good saws at all? Just some bearing issues and that's it?

Yes.

 

[o8f150]

I run 45/1 in all my saws but I do run them on the rich side

 

[mdavlee]

I've replaced some cranks that lost the big end in a month of runtime out west in ported saws cutting 6 hours a day.

 

[duramax99]

yah 390s don't seem to like a lot of rpm....

 

[husq2100]

should have got the best 88cc Husky


















288xp high top.

 

[Dieselshawn]

Thanks everyone, I passed on all the info provided by this forum. The saw shop is gonna speak to the saw owner when he comes to pick up the rebuilt units about increasing the life of his 390's.

Duramax99: That's not good looking in the photo. Hopefully it's been rebuilt and back in action doing what it does best.

 

[Philip Wheelock]

...The saw shop is gonna speak to the saw owner when he comes to pick up the rebuilt units about increasing the life of his 390's...

Maybe neither here nor there, but my local repair tech advised me to cut with the saw loaded enough so the motor stays in it's power range; in other words, limbing with an MS440 at 12,500 rpm's will wreck the bottom end sooner than later.

 

[mdavlee]

But what if they'll turn 12.5k in the wood?

 

[Philip Wheelock]

...limbing with an MS440 at 12,500 rpm's will wreck the bottom end sooner than later.

But what if they'll turn 12.5k in the wood?

I guess the tech's point was to keep a bigger stock saw in wood big enough so it stays around its maximum power rpm, which is listed for a 390 as 9,600 rpm. Saws modded to run with more power at higher rpm's are a different story. Smaller wood? Use a smaller saw maybe. Also, running 32:1 gas/oil mix is the first thing to do.

 

[mdavlee]

I'm sure it does add wear to the bottom end. That may be why the saws used out west don't last as long before a rebuild. They're limbing with them all day when they're not making felling cuts or bucking.

 

[Philip Wheelock]

I'm sure it does add wear to the bottom end. That may be why the saws used out west don't last as long before a rebuild. They're limbing with them all day when they're not making felling cuts or bucking.

Back in Massachusetts, I heard crew maintaining the power line right-of-way across our property a few months ago. Basically limbing at constant WOT, saws screaming. No need for that. OTOH, I suppose loggers use one big saw for everything.

 

[mdavlee]

Thinning crews seem to be hard on equipment. I don't use small saws either so I do all my limbing with. A 70-90cc saw also.

 

[Andyshine77]

A local crew chief once said. Sometimes they mix too much oil, sometimes not enough. They run 211's until they die, they were burning up pro saws left and right, so they went with the cheap ones. The chief did speak a little English, which was a plus.