372xp issues

[slambox28]

The old cyl squish (see where the rings stop at the bottom)

 

[slambox28]

Farmertec squish: zeroed out (piston taps the cyl by the thousadnths)

 

[slambox28]

Pull the cylinder and check for bad crank bearings

How do I check the bearings? With an oily finger I can spin the inner bearing race. The only thing I notice is the inner bearing race seems a bit notchy to start off the spin even now after extensive cleaning. Once it starts then it seems like brand new. (bearings are still in the case now). Spinning back and forth there's no catch at all. Every few turns making full rotations on the inner race it catches when using an oily finger. It seems like debris is in the bearing but the more cleaning and blowing out it still doesn't change. The entire saw is filthy, so I figured its just sand or dust but cant get "it" out.

I guess I better replace bearings now, is that common for such a slight defect to put a saw out of service with noticeable problems?

 

[Czed]

How do I check the bearings? With an oily finger I can spin the inner bearing race. The only thing I notice is the inner bearing race seems a bit notchy to start off the spin even now after extensive cleaning. Once it starts then it seems like brand new. (bearings are still in the case now). Spinning back and forth there's no catch at all. Every few turns on the inner race it catches when using an oily finger. It seems like debris is in the bearing but the more cleaning and blowing out it still doesn't change. The entire saw is filthy, so I figured its just sand or dust but cant get "it" out.

I guess I better replace bearings now, is that common for such a slight defect to put a saw out of service with noticeable problems?

Just do yourself a favor and change the bearings then start from there
Make sure to get quality bearings from anyone
Nachi or whatever.

 

[slambox28]

Just do yourself a favor and change the bearings then start from there
Make sure to get quality bearings from anyone
Nachi or whatever.

Yep I think you're right. Ah I'm starting to realize now how the piston in the cylinder isn't going to have all the leverage you have when checking with the cylinder off... ya I better swap those out for sure! Thank you!

 

[slambox28]

Now the piston rod roller bearing: I can't feel any play at all with push/pulling forces. It seems like brand new. And it's a roller bearing so I'd think it will be ok to keep in the saw as is (lots of surface area). There's only some side load wobble but it seems that should be normal for a needle bearing like this on a round shaft with a plastic collector. I'd think this should be no issue at all.

 

[hacskaroly]

Crank bearings: they have no play at all and a very tight fitment, not loose at all. Seem to be in brand new shape. But now after more and more testing I've realized they might not just have debris. When fully rotating several times in the same direction it starts to catch every time; after several rotations of the inside race in the same direction. (the bearings are in the case still). But moving back and forth like before they seem like brand new. Not when going in the same direction though. Before, I thought it was just some debris but after cleaning and spinning, blowing them out and adding oil the "debris" is not going away? Maybe it actually is the bearings?

I was working on a Husky 55 a couple of weeks ago, it had a bad oil seal on the clutch side. I pulled the oil seal and the back side was crusty with oil, looked at the bearing and it was all crusty too. I started cleaning with break clean and chunks came off and got caught up in the bearing preventing it from rotating. I was finally able to get it all cleaned out and the bearing moving freely. If it was my saw I would have changed the bearings. I also worked on a 391 that had a plastic race that keeps the bearings separated, that plastic broke in a couple of places and allowed the bearings to become uneven in spacing.

As for your piston knocking...I doubt the crank stretched, it doesn't sound like you were running the saw long enough or hot enough to do that. Maybe if you were milling 30' boards of black locust on a +100 degree day for hours without stopping...then maybe.

 

[Czed]

Now the piston rod roller bearing: I can't feel any play at all with push/pulling forces. It seems like brand new. And it's a roller bearing so I'd think it will be ok to keep in the saw as is (lots of surface area). There's only some side load wobble but it seems that should be normal for a needle bearing like this on a round shaft with a plastic collector. I'd think this should be no issue at all.

A little advice
I've built several dozen 2165/2171/371/372s
Clean up and use the OEM cylinder you will not get more power with the aftermarket stuff 50mm or 52mm
Without porting
The 50mm hyway popup 372 pistons do ok in the oem cylinders.
New crank bearings and seals and you'll have a reliable saw
As far as porting i send mine to the guy's here they have proven recipes for strong running saws
Zoo city, stumpshot, mastermind, XS worksaws,cfb it's well worth not ruining a increasingly hard to find oem 372 cylinder having someone professional port it.
Some will do cylinder only to save on shipping costs

 

[Woodpecker]

A little advice
I've built several dozen 2175/2171/371/372s
Clean up and use the OEM cylinder you will not get more power with the aftermarket stuff 50mm or 52mm
Without porting
The 50mm hyway popup 372 pistons do ok in the oem cylinders.
New crank bearings and seals and you'll have a reliable saw
As far as porting i send mine to the guy's here they have proven recipes for strong running saws
Zoo city, stumpshot, mastermind, XS worksaws,cfb it's well worth not ruining a increasingly hard to find oem 372 cylinder having someone professional port it.
Some will do cylinder only to save on shipping costs

Ding ding best answer… K.I.S.S

 

[Woodwackr]

The old and new both have the exact same behaviors, but no visible marking/indention on the old piston? my guess is that possibly it's hardened overtime from heat/cooling? but idk that doesn't seem like a realistic reason why, just can't think of any others

Chainsaw motors really don't do that which is why this is confusing.

 

[Woodwackr]

Another new finding: the ring thicknesses are actually the same for both pistons. This picture shows the regular ring (back) and the sanded down ring (front). I sanded down the ring to fit. Maybe from working in the dark barn w/o sufficient lighting for this, notice the loose fitment on the front ring it slants downwards.
View attachment 436272

372s use a 1.2mm, not a 1.5mm ring, I believe. At least the 371 does

 

[Woodpecker]

Stretched the piston rod or the crankshaft

The only thing I can put a finger on is that the piston rod or some part of the crank stretched.

Hmmm… tell us more about your stretched rod? Length, girth, etc. precise measurements will be needed. Maybe @Kiwioilboiler can get to the bottom of this mythtery… he’s the resident stretched rod expert.

 

[Canadian farm boy]

Here is the contact impression on the piston. Taking material off the piston face could work too. Much easier and quicker but without the benefits of porting.
View attachment 436261

IMO that’s not head slapper marks. Those look like marks left on the piston during shipping. The pistons are usually placed loosely inside the cylinder from the manufacturer and vibrate around in transit leaving those marks.

 

[Creaky Limb T C]

the new gasket is non-OE, not sure what brand it is.

Chinese rubbish

 

[Woodwackr]

What a cluster....

 

[slambox28]

I was working on a Husky 55 a couple of weeks ago, it had a bad oil seal on the clutch side. I pulled the oil seal and the back side was crusty with oil, looked at the bearing and it was all crusty too. I started cleaning with break clean and chunks came off and got caught up in the bearing preventing it from rotating. I was finally able to get it all cleaned out and the bearing moving freely. If it was my saw I would have changed the bearings. I also worked on a 391 that had a plastic race that keeps the bearings separated, that plastic broke in a couple of places and allowed the bearings to become uneven in spacing.

As for your piston knocking...I doubt the crank stretched, it doesn't sound like you were running the saw long enough or hot enough to do that. Maybe if you were milling 30' boards of black locust on a +100 degree day for hours without stopping...then maybe.

Oh, all good to know. Yep the piston markings made me think something stretched. I never considered that as a possibility until the YT video about it. It seemed like nothing else wrong. The bearings never had any unusual symptoms I never even considered the possibility of them being bad. Apparently, it must be bearings after very close inspection and testing. Very slight gritty feeling turns out not to be debri. It's so unnoticeable that I never would've considered it could cause this issue, but now after thinking more it might be the very problem. Thanks

 

[slambox28]

IMO that’s not head slapper marks. Those look like marks left on the piston during shipping. The pistons are usually placed loosely inside the cylinder from the manufacturer and vibrate around in transit leaving those marks.

Yep I think you're right on that. The piston did come in the cylinder out of the box

 

[slambox28]

372s use a 1.2mm, not a 1.5mm ring, I believe. At least the 371 does

Yep I think you're right, the ring mics at 1.2mm. There is 2 sizes, when it didn't fit the old piston I sanded one new down to fit. (snapped one of the old rings)

 

[slambox28]

Hmmm… tell us more about your stretched rod? Length, girth, etc. precise measurements will be needed. Maybe @Kiwioilboiler can get to the bottom of this mythtery… he’s the resident stretched rod expert.

Hahahahaha (yo mama knows about it just ask ) no rods stretched only theories hahahahahaha

 

[slambox28]

A little advice
I've built several dozen 2165/2171/371/372s
Clean up and use the OEM cylinder you will not get more power with the aftermarket stuff 50mm or 52mm
Without porting
The 50mm hyway popup 372 pistons do ok in the oem cylinders.
New crank bearings and seals and you'll have a reliable saw
As far as porting i send mine to the guy's here they have proven recipes for strong running saws
Zoo city, stumpshot, mastermind, XS worksaws,cfb it's well worth not ruining a increasingly hard to find oem 372 cylinder having someone professional port it.
Some will do cylinder only to save on shipping costs

That's all good to know. Ya the cylinder I thought is a new big bore like the ebay ad said. I wouldn't shave out the top of the old cylinder for sure, I only was going to do that with the farmertec. A bunch of cutting coming up, I'd like to run the old cylinder and possibly in the future try on the 52 farmertec. I might even try porting the farmertec as an experimental run but on the other hand probably not because of the cost, time and effort of setting up a fixture. Thanks!