385xp wrist pin failure

[fatboycowen]

So, i had a tree climber take down 3 huge pines a few weeks ago, and leave them for me to cut up. Pretty big suckers, at least 30" dia. at the base.

I was running my 385 xp. After a cut, when the saw idled down, i could hear a clacking noise, which sounded like the piston was hitting the top of the cylinder, so i shut down, and hoped it was just something stuck in the flywheel. Well, the saw wouldn't turn over all the way with the pull cord. Not locked up, but stopped just before TDC. I figured the big end bearing crapped out. Turns out it was the wrist pin bearing. Damn thing crapped out just as i was about to slap on the 32" bar for the biggest pieces. Ended up finishing it up with the 562 and a 24" bar, which handled it nicely.

I rebuilt this saw a few years ago. New crank bearings, meteor piston (with wrist pin), and a huge list of other things. I was a little worried about the crank big end bearing, but ended up re-using the crank. I think, being a noob, i thought it had play, but it doesn't. It still doesn't seem to. The saw ran amazing, and was super strong. I figure i have maybe 10 to 15 tanks through it since. BTW, i'm running 32:1. I had been running Stihl Ultra, but just switched to Lucas semi-synthetic to try that. I think this has 1 tank of that through it.

Here are some photos, if they upload correctly.

It appears that the jug is ok (phew). The squish area has some dings, but i can't see any real scratches on the cylinder walls. Piston got messed up, but it didn't seem to affect the jug.
I'm not sure if you can see it in the photos, but the bottom of the crank case, near the center, got scraped by the pieces, when it got squished between the small end of the crank and the case.

The small end of the crank feels smooth, like nothing is wrong. Do i need a crank?

A part of me is tempted to ship this to a builder, and have it fixed and ported. The saw was so strong , i can't imagine a ported version.

Thought?
Jon

 

[nmurph]

How did the bearing come apart if the circlips didn't let go first?

A ported 385 is a beast.

 

[fatboycowen]

Circlips were perfectly intact. I removed them (after taking pics of the piston and little metal chunks). The wrist pin was a ***** to slide out. I had to put a screwdriver in and tap it out. I think the bearing cage gave up, and maybe pieced of it, or the needle bearings, made their way out the little holes in the crank, or maybe at the little indents on the bottom of the piston.

I couldn't find anything else wrong. I was able to view the crank bearings, and the cages seem to be intact, and everything rolls smooth.

 

[redoakneck]

Good time to get it ported IMHO

 

[nmurph]

It definitely needs to come totally apart to be sure that all traces of the shrapnel is removed. 385's have an updated PTO side bearing. They are prone to developing an air leak bw the inner bearing race and the crank. The updated bearing will come with the seal installed for about (gulp) a Stihl-like $40 0r so. The FW side uses an off the shelf 6203.

 

[blsnelling]

I can't imagine that crank being any good. That is the outer race for the needle bearing. It needs to be perfectly smooth, or a new bearing won't last long at all.

 

[Jacob J.]

Yeah, if there's any marks at all on the inside of the small end of the connecting rod, it's likely no good. If it cleans up well and the big end rod bearing is still tight, then you might be good to go. I agree with Neal though, that case should come apart and get the updated PTO bearing and new flywheel side bearing.

 

[fatboycowen]

I should have the update bearing. It wasn't cheap. The crank had some wear and was spinning inside the old pto bearing when I got the saw. I'm assuming it leaked, but I didn't see any signs of it. I used the loctite bearing retainer stuff and installed it, which seemed to work well.

If I get it ported, I'd want to buy a crank, since I'd be investing so much.

What's a crank cost?

 

[HuskStihl]

Was that the original bearing? I put a meteor in mine and reused the original wrist pin bearing. Maybe a mistake.

 

[mdavlee]

Crank is around $200 or a little more. I bought one a few years back.

 

[RiverRat2]

definitely worth refurbishing,,,

I have to get on the band wagon W/Neil & JJ, while you have it apart, upgrade/new brgs./seals. That class saw new is 9 bills. It would be optimal for U if the rod/crank isn't toast,,,,

 

[fatboycowen]

It sucks. I. Already have the updated stuff. I'm pretty sure I used the bearing that came with the meteor piston kit.

 

[Jacob J.]

It sucks. I. Already have the updated stuff. I'm pretty sure I used the bearing that came with the meteor piston kit.

The Meteor piston kits don't come with any bearings.

 

[nmurph]

Meteor kits don't come with bearings that I've ever seen...and I've used several for 385's.

 

[fatboycowen]

OK. Then I used the one I got from weedeaterman. I got a bunch of stuff from them, gaskets, carb kit, rings, etc.

I guess the aftermarket bearing was a bad idea, assuming it was aftermarket.

 

[nmurph]

If it's aftermarket, it's not the first wrist pin bearing I've heard of failing.

 

[Jacob J.]

I don't do the aftermarket wrist pin bearings in any saw. Good condition used OEM is better than new aftermarket in that application any day.

 

[HuskStihl]

I don't do the aftermarket wrist pin bearings in any saw. Good condition used OEM is better than new aftermarket in that application any day.

Glad to hear it!

 

[nmurph]

I've gotten quite a few of these AM WP bearings when I bought Meteor pistons (NOT A PART OF THE KIT...JUST EXTRA'S ADDED INTO THE BOX). They go straight from the package to the trash so they don't get mistakenly used in place of an OEM.

 

[gaspipe]

Yikes. I can't remember which wp bearing I just put in my 385. I guess I'm taking it apart again, and might as well get the jug ported and change the PTO seal while it's on the bench.