Husqvarna 372 piston skirt

[Mattymci]

I opened up a running 372 and and the piston is damaged on the intake side and worn right through where the two cases meet. The cases are a little uneven where they meet on that side and I can only assume that the piston was catching on the cases. I’m going to replace the piston but I don’t know why it or how it was catching on the case. Should I smooth out that lip with a Dremel?

 

[lostone]

Cylinder pics please. Particularly towards the inside of the lip on the intake side.

 

[TLG]

Call me crazy but looks as if your cylinder may have been run loose. Also possibly taking off some cylinder side fins and running them through the flywheel. If it rocked hard enough the connecting rod would of worn/broke through the piston skirt as shown. Would also like to look at the cylinder ass.

Sent from my XT1635-01 using Tapatalk

 

[Mattymci]

That makes sense, there is some scoring in the cylinder but looks like i may be able to clean it up.

 

[TLG]

Would like to see the intake side of Conn. rod beam. Also don't know why your cylinder base looks freshly cut? Has no patterns as your crankcase does along with the intake side being so clean?

Sent from my XT1635-01 using Tapatalk

 

[TLG]

So what's up on the cyl,'s. The second pic. shows wear, scratches, and base wear. The first cyl pic is what a ported cyl to install in place of failure?

Sent from my XT1635-01 using Tapatalk

 

[Mattymci]

Someone posted a pic in a reply, the pic I posted is the saw

 

[TLG]

My bad, I see now the first cyl pic is from lostone and not your failed cylinder. LOL!!!

Sent from my XT1635-01 using Tapatalk

 

[Mattymci]

The damage to the piston lines up exactly with thetwo halves of the case
.

 

[Mattymci]

The saw actually ran like that, I picked it up for cheap and tore it down

 

[lostone]

Plating has been cut through below the lower intake port edge. Did someone try to port this cylinder?

 

[lostone]

Either way I would say you are looking at a new P/C kit. You can pick up an OEM for $115. But check everything else out before getting new stuff.

 

[Mattymci]

But that makes a lot of sense that someone may have run the cylinder loose. That’s the only spot with scoring on the cylinder, I’m hoping it cleans up with acid

 

[TLG]

I had a 3400 Poulan that had the cylinder base come loose on it. If I hadn't seen it for myself I wouldn't of believed it. It also ran and didn't seem like it had a lean air leak issue. Although it was a little noisy.

Sent from my XT1635-01 using Tapatalk

 

[TLG]

Just a suggestion before you build it up with a new cylinder. Have a machine shop parallel grind the base mount area of the crankcase enough to true it up. This will help prevent an air leak. Definitely check your squish going back together. As you may have to add an extra gasket or make one out of thicker paper.

Sent from my XT1635-01 using Tapatalk

 

[Marshy]

The mismatch in the case is not the cause of the piston failure. The cylinder base skirt covers that spot in the case.

 

[lostone]

The mismatch in the case is not the cause of the piston failure. The cylinder base skirt covers that spot in the case.

Thats why I needed the pics of the cylinder, it shows where everything went wrong. I figured seeing it was easier than explaining it.

 

[TBS]

Looks like someone got aggressive with sanding down the piston, the skirt looks real thin right there and was most likely cracked because the previous problem.

 

[huskihl]

It’s usually one of three things. Either the cylinder bolts backed out, the crank bearings are bad, or something like a screw got sucked through the carburetor, but that usually leaves pretty good scoring where it came up through the transfers or at the exhaust outlet also

 

[lostone]

When I expand your image up to max size the spot inside the red box looks like it's dug in pretty good. Then look above the yellow line, you can see where the ring has been clipping the bevel, which could have happened if the cylinder was loose. Also looking at how smooth the intake is inside. It's like this cylinder is an attempt at porting, also look to the left of the red box at max size and see the uneven step and notice how most of the streaking is from the bottom of the intake downward towards the crankcase when the cylinder is turned right side up, which again could be from a loose cylinder.

When you took it apart, where the cylinder bolts loose?

Like was mentioned above check out the rod bearing, I would also check out the main bearings and seals, if some of that ended up inside the crankcase then those are areas that will be at risk.