Excessive Pin Boss Clearance on MS361 Hyway Pistons

[PogoInTheWoods]

Received this piston in a Hyway MS361 p/c kit. Looks to me like needle cage failure waiting to happen. How can they be this far off with something so simple to replicate..., or do they expect this to be acceptable? Sheesh.

Would any of you put this piston in a MS361 rebuild for a tree service?

OEM below.

​

 

[BuckthornBonnie]

Had a similar piston in a ms390. I used it.

 

[BuckthornBonnie]

It's a personal beater saw so if it goes it won't be a big deal. Few pics-
Oem 440-


Oem vs. Meteor 440

Meteor in position-

Oem 290-

 

[BuckthornBonnie]

So both my AM 390 and your AM 361 have excessive clearance compared to oem and better AM. Would it cause a premature failure? I'm not sure... but I'm damn curious.

 

[PogoInTheWoods]

I really don't want to find out the hard way from a valued tree service customer. And it's not a cheap kit as these kits go, so...

Only reason I didn't go with a Meteor kit is they don't make one...just the piston. Plus a Stihl piston is only $37 anyway. Cylinder wasn't salvageable, plus I've used very nice Hyway kits in the past. Just disappointed in this one and wonder if the pistons are all like this?

 

[BuckthornBonnie]

I wouldn't use that piston for your tree service customer. I haven't used a Hyway for this series... only 1125s.

 

[BuckthornBonnie]

Even AS is slow to respond.

 

[BuckthornBonnie]

Dave has Meteors for $34 shipped or the $37 oem as you mentioned. If you like that jug then that's the way I'd go.

This reminds me of the 044 meteor problem AdirondackStihl discovered a few years ago. I don't think anyone reported a failure, but it just didn't seem right.

 

[PogoInTheWoods]

Yeah, I figured this topic would generate a bit more traffic between the two forums. I ran into the same problem with an AM 262 piston a while back. Didn't use that one either.

Now to see if the vendor will make it right...

 

[PogoInTheWoods]

Got credit for the piston. They (HLS) offered to exchange it for a Meteor but I went with the Stihl for another coupla bux because I have a great dealer a mile away that will do special orders for me without charging anything extra for shipping. I can get stuff the next business day if I order before 3:00pm the day before. Can't beat that. HLS is great, too. Just didn't want to wait until the end of next week (because of the 4th) for a replacement when I can have one in my hands on Monday.

 

[Lightning Performance]

Looks like they used an 044 inner mold/cast plate by mistake.

 

[PogoInTheWoods]

That would actually be narrower, not wider. The 044 uses a 13mm (wide) needle cage for both the 10mm and 12mm diameter wrist pins. The MS361 is 15mm.

Interestingly though, (regarding the piston itself), the newer MS361 pistons have smaller windows with a lot more internal flow volume and less mass in general. Curious porting design modification.

 

[Lightning Performance]

Over 15mm wide and a 11mm pin. What saw has that?

 

[exSW]

Over 15mm wide and a 11mm pin. What saw has that?

Shindaiwa 680 has an 11 mm pin and a wide gap for thrust washers. But it's 49mm not 47 like a stock 361. Plus no one makes an aftermarket for it.

 

[PogoInTheWoods]

Over 15mm wide and a 11mm pin. What saw has that?

Uhhh..., the MS361.

 

[Gentleman]

Received this piston in a Hyway MS361 p/c kit. Looks to me like needle cage failure waiting to happen. How can they be this far off with something so simple to replicate..., or do they expect this to be acceptable? Sheesh.

Would any of you put this piston in a MS361 rebuild for a tree service?

View attachment 75958

View attachment 75959

OEM below.

View attachment 75960​

I have forwarded this to Hyway. Let you know what they say.
What is the measurement on the OEM piston?

Did you buy from us?

 

[PogoInTheWoods]

Yes, it was from you folks. (See post #10)

Kaity was great when I called about it. Even broke out some calipers herself to measure a Meteor for comparison. OEM is 15.25mm between pin bosses and the Meteor was real close. The Hyway was 19.5 or so. Said she would set it aside to send back as defective when it was returned. Hope so. Seems like an easy fix, or as was suggested, maybe just the wrong inner mold/casting piece was used for a particular run. I can't imagine they'd be that far off original specs on purpose. Some of the other no-name repops, maybe.

As another interesting aspect, the cylinder was really nice aside from some easily manageable nonsense in the intake and exhaust ports. Plating and transfers were very nice. Squish was super tight with no base gasket...as in the OEM piston hits. Just a hair of a difference in the piston height from the Hyway, though a .020 gasket (minimum) would seem to be a requirement unless one was to do some combustion chamber/squish band work instead. Squish was around .045 on this particular cylinder which is about the thickness of a stock OEM gasket.

 

[wcorey]

Wanna see a really nice 361 kit, check out the Tecomec.
Pretty nice price too...

http://www.hlsproparts.com/mobile/Product.aspx?ProductCode=570005-TEC

 

[PogoInTheWoods]

Was considering the Tecomec but hadn't heard much about the quality of their product's recent foray into that price range. May need to try one of those for my own 361 project in a box. Price sure can't be beat for a NiSi kit.

 

[Wood Doctor]

Good thread. Glad my MS361 is running strong today after nine years and 60o operating hours. Here it is 9 years ago:


BTW: if anyone has trouble seeing this pic on their machine, please advise. Photobucket is giving me fits these days.