to rebuild or not?

[jmemmert]

That is the question:

I bought an ms 361 that has the piston scuffed up on the exhaust side, and a little on the intake side. I assume this is from a poor mixture, or running it hard before letting it warm up. Looking through the spark plug hole, there appears to be some scuffing on the cylinder wall. it dosn't look too bad, It may clean up.

Here is my problem, the saw runs decent, has good power and all. The PO told me it only had 135# of compression. I went ahead and ordered a new piston kit for it from Amicks.

I bought a cheapo harbor freight compression tester. I have checked the compression on the 361, and came up with 160 on 4 pulls, cold.

I thought, dang, my tester sucks Its way off, so I checked my 034 that has very few hours on it. I came up with 165# in 3 pulls cold.

Should I :

Rebuild the 361 with the new piston I've already paid for?

Just run it till it quits for good?

Or sell it on ebay to get my money out of it?

Thanks,

Jon

 

[blsnelling]

No way would I run it with the scored piston. You're likely to seize it and maybe ruin the cylinder. It only takes a few minutes to pop that new Meteor piston in there. I'm assuming you cleaned up the aluminum that was transfered to the cylinder? How did you go about that?

 

[jmemmert]

I havn't taken off the cylinder yet. I guess I'll go ahead and do that now since you reccommend not running it.

If there is transfer, I plan on using acid, and then using some 180 grit? to put a new cross hatch in it.

Also, will I need a new base gasket, or can I reuse the old one?

 

[davefr]

A lot of saws run just fine and serve long lives with mild scoring (can you post some images?). Your compression test looks pretty good. How well does the saw perform in the field?

Your options:
1. Just cut wood
2. Clean it up as best you can (scotch brite, acid, etc) and then proceed to option #1.
3. Replace piston or piston/cylinder.

I'd do #2 if the saw currently performs well. The cylinder is easy to remove and then you can better assess it's overall condition.

If the saw is a like new "cream puff" except for the scoring then I'd probably do #3 (P/C kit) but it's not always needed.

P.S. Throw on a new gasket and I'm not sure 180 grit is correct. That sounds way too course for cross hatching.

 

[jmemmert]

I should have the tools to do it tonight. It is in awesome shape, It looks almost new other than the muffler paint is burnt off, and the bottom of the case has the paint warn off. It still has the sticker on the front of the case.

I'll try to post some pics when I get a chance.

 

[blsnelling]

If there is any real scoring, that will simply promote further scoring and possibly lead to a seizure. As cheap as a piston is and as easy as it is to install, I wouldn't risk ruining the cylinder and you'll know it's right.

I would start with acid. I wouldn't go as coarse as 180 grit. That's pretty strong. I like to use wet/dry paper with a little lubricant on it, something like PB Blaster. I would use a new gasket, although I have reused them before since they're rubber coated.

 

[Lakeside53]

There's a big difference between light scuffing and significant scoring...

I seem many scuffed pistions in saws that run fine. If I pulled them all down, I'd have a lot of pissed customers.

Yes.. it's matter of degree, but given your compression (subject to inspection) I'd likely stay with the OEM piston. If you're going to pull it down, put in a new oem base gasket - they are deformable "use once only" type.

The factory hone finish cylinder is extremly fine. Even 320 paper is pretty coarse. You need to simulate a crosshatch, so that requires the paper to rotate as you pull it in and out of the cylinder. Horizontal lines are terrible... If in doubt, use a fine scotchbite only.


Pictures?

 

[davefr]

Jon,
Maybe this will help. Someone posted it not to long ago:

 

[jmemmert]

The cylinder had a little aluminum transfer, but cleaned up nicely with acid. I used 240 wet sand paper, and some wd-40 to put a new cross-hatch in. You can still seen the scuffs, but can't feel them at all. The oem piston was toast.

I put it all together, and discovered that the piston skirts on the meteor piston were just slightly too thick, and were hitting the crank at bottom dead center. I filed a bit off, and it cycles through well now.

I told Tony at Amick's about it, and he offered a full refund. We decided to just file the skirts a bit to make this one work. He is sending me new retaining clips too. Thanks Tony!

When I get the clips in, I'll re-assemble and let you all know how it is working out.

 

[Lakeside53]

I put it all together, and discovered that the piston skirts on the meteor piston were just slightly too thick, and were hitting the crank at bottom dead center. I filed a bit off, and it cycles through well now.

:bang::bang::bang:

What is it with these dumb manufacturers? How frigg'in hard is it to make a GOOD copy???? I guess I'll cross another aftermarket brand off the list.

 

[AZLOGGER]

:bang::bang::bang:

What is it with these dumb manufacturers? How frigg'in hard is it to make a GOOD copy???? I guess I'll cross another aftermarket brand off the list.

:agree2:

Lake I have seen that too, customers bringing chainsaws in with "El Cheapo" pistons and P/C and want me to install the parts for them, because I have the special tools needed for installations. Some of that crap has so much casting flash left on it, I'd be ashamed to try and sell it. The real ass kicker is it's never in a box, so I do not know who manufactured it, also they don't get the job done here.

Kinda reminds me of the poster of the guy taking his own steak into a restaurant and asking them to cook it for him. :censored: e'm

 

[jmemmert]

I hear you guys. It shouldn't be too tough to get it right. Other than that little issue, I am pretty pleased with the quality of the Meteor Piston.

 

[blsnelling]

The cylinder had a little aluminum transfer....The oem piston was toast.

It's a good thing you went in there!

I don't see this skirt issue as a reason to totally dismiss this brand. Obviously they've got some issues they need to address, but it's likely still a good piston. It they were good before, they're still good now. They just have a fitment issue.

 

[davefr]

It they were good before, they're still good now. They just have a fitment issue.

Yea, just minor details - a piston that won't fit.

 

[Lakeside53]

Brad - B.S... it shows a complete lack of engineering disipline, and worthless QA/QC... Why would anyone have faith in anything they make if crap like this gets to retail? We see it time and time again... from multiple vendors - included the orginal and some subsequent BB kits from AS's favorite vendor.

How does stuff like this get screwed up? ' cos they are making it as cheap as possible, shove it out the door and just don't care. Want to bet the rest of the inventory from the same batch (bet they don't even have traceable batch numbers) is exactly the same - made wrong...

Why should Joe Public be the beta testers.... which is what anyone that buys this stuff is...?

 

[blsnelling]

Brad - B.S...

Hey. I resemble that remark. That's my initials

I agree and disagree, just for the sake of arguement on a cold winter night. If you used these before and the quality was ok, then it's still ok. In other words, if it ran good and held up before it still will now. I don't see it being that big of a deal to have to relieve the piston skirt a little.

On the other hand, you can make the arguement that you just did. If they can't even get the diminestion right, what can you trust about it?

Here's the bottom line for me. If critical dimensions like piston to cylinder tolerances are acceptable, then I can take care of something like skirt clearance. If I'm competent enough to be installing a piston to begin with, I'm certainly capable of clearancing the skirt. But I sure shouldn't have to. If they can get the bore right, you'd sure think they could get the skirt length and width right.

Yep, you're right. I just walked right down the middle of the fence. I'll likely fall and straddle that sucker and be licking my wounds in a few more posts here. Enjoy the hot cocoa around the fire guys

 

[stihl86]

Well, if they had engineering, manufacturing and the quality control, wouldn't that make them as much as OEM? You get what you pay for. It's not the Chinese manufacturers, it's the vendor.

 

[Lakeside53]

Some companies would call them seconds.. real companies would throw them back into the smelter.


That these even make it to market - I call it pathetic.

 

[Lakeside53]

Well, if they had engineering, manufacturing and the quality control, wouldn't that make them as much as OEM? You get what you pay for. It's not the Chinese manufacturers, it's the vendor.

nope... I bet Mahle and Stihl make them for little more then the dumb fools that think they can make a recycled Matag into a piston. Hey, maybe the dumb fools are the end users...


Aftermarket car parts cost a fraction of the OEM, and they have real process control...

 

[jmemmert]

Hey, maybe the dumb fools are the end users...


Gee, thanks Lake!!! A real confidence builder there.