Husky 372 top end evaluation-puzzled a bit

[Frank Savage]

Hi guys,

got a well used, but running Husqvarna 372XP to make it a nice runner for mainly hardwoods and overall a sturdy mid-size saw. It was not well cared for, seems to me that at one point was run on hell knows what oil and the capability to tune the carb was pretty poor at both last two owners-but I knew that and counted for a little greater overhaul. After teardown, I´m a bit puzzled by condition of the top end, which in the worst scenario may indicate a worn bottom end but-well, hold on the line.

First, there is visible and "nailable" fleck of different material below the intake port. Seems to me like material from the piston, since there is some pitting and absolutely no toolmarks left at that part of the skirt:

Then, there is a small nick in the nicasil about 1/8" above top of the exhaust port, between the exhaust and front left transfer port. So far I have seen such mark only when there was an imperfection or bubble in the cylinder wall, so the Nicasil failed there, or when a bit stuck ring suddenly sprung back. Not sure about any void, but the stuck ring could have easily happened:

The piston has several quite severe blow-by streaks. No melting, but smoked as ham. The longest is just on the oposite side than the nick in the cylinder plating, where the wall is absolutely clean, so there is no connection between those two. There are very little toolmarks left, mainly above the piston ring, but they are vanished on the sides above the ring and on the front/aft of the skirt below the ring. Streak here:

The wear pattern leads me to suspicion that there is irregular ovality in the bore and maybe the crankshaft is shot, having too much sideplay (the top of connection rod has a bit less than 1/2" side-to-side wiggle, but this does not seems to me to be a problem.
The better possibility is, that there is a material transfer on the cylinder wall and the irregularity in piston wear and blow-by was caused by stuck ring from poor oil.

What do you think about it?

I did not any definitive proof test about material transfer, for the reason if it is worn Nicasil and exposed cylinder wall, I can have it replated for a bit less than price of most Non-OEM cylinders around here-so I don´t want to make it wose for grinder by trying to sand it off.
The location is quite strange to me, but there is a lot I´ve not seen so far I believe.


If it is transfer, I´m gonna slap a Meteor piston in there, do some cleaning, smoothing and minor port job, muff mod and put her back.
If there are worries from the knowlegeable about the top end being toast, a new one is on schedule-and here I´m a bit torn between standard or big bore kit, since capability to pull plunged 22" or 24" ful comp in seasoned oak as a top workload is desirable. No extra fast cutting, then, but mean steady when keeping her in powerband (yep, I know a 272 would be better here, but 10"-20" conifers in mixed forrest is gonna be better with a 372)

 

[lone wolf]

IDK but from what I see the nikasil plating looks worn off the cylinder.

 

[burnses]

I think ya got plating loss at the base of the port which tells me the plating might be getting thin in other areas....if it was my own personal saw and was going to work for fire wood I might run that cylinder if couldn't find a better used one....a fresh piston might not tip over at bdc so bad and continue to wear the bottom of the cylinder....hard to tell how bad the plating loss up top is....

good luck

 

[Jacob J.]

That wear under the intake port is usually due to running an unusually dirty air filter for prolonged periods.

 

[Frank Savage]

OK, so used the ultimate tools-toolsteel scraper with perfectly straight edge, 600 and 1000 grit emery cloth. There was some transfer, but below the intake port, there was quite considerable falloff-measurement revealed the piston skirt had about 0,026 clearance there, so it was banging against the wall and as a result, thin surface layer peeld off with remains of the plating, so the exposed aluminium spot is about 1,5 the original width.

Jacob J.-thanks, didn´t even think that way-haven´t ever seen such dirty filter. But in the light of your notice, the way where the saw was dirty and the kind of sawdust tells clearly it was used as a milling saw for some time. Now it makes sense.


So the cylinder is toast, even when my living realy does not depend on it. The connection rod can be wiggled to side less than 1/8", not 1/2 as stated yesteraday-so the bottom end can be considered useable I think.
Now the crucial question-to go big bore, or not to go big bore

 

[lone wolf]

OK, so used the ultimate tools-toolsteel scraper with perfectly straight edge, 600 and 1000 grit emery cloth. There was some transfer, but below the intake port, there was quite considerable falloff-measurement revealed the piston skirt had about 0,026 clearance there, so it was banging against the wall and as a result, thin surface layer peeld off with remains of the plating, so the exposed aluminium spot is about 1,5 the original width.

Jacob J.-thanks, didn´t even think that way-haven´t ever seen such dirty filter. But in the light of your notice, the way where the saw was dirty and the kind of sawdust tells clearly it was used as a milling saw for some time. Now it makes sense.


So the cylinder is toast, even when my living realy does not depend on it. The connection rod can be wiggled to side less than 1/8", not 1/2 as stated yesteraday-so the bottom end can be considered useable I think.
Now the crucial question-to go big bore, or not to go big bore

Stay OEM more reliable.

 

[Onan18]

If you want a big bore get the OEM 51.4mm XPW top end, contact Spike60 or Terry at Wicked Work Saws for a good price.

Joe

 

[blsnelling]

All rods will wiggle left to right, even new ones. The question is, does it have any radial play?

Yes, the NiSi is worn through.

 

[Frank Savage]

Can´t detect radial play, by hand nor by using vice, stand and machinist micrometer-some tolerance is there, but about 0,0005 or so. I´m familiar with the usual wiggle, but this seems to be a bit on edge (well, I´m known to be somehow anal on some things).
After examining the crankshaft and finding that clutch side bearing will need some Loctite help to be as tight as should be upon reassembly, I´m going for standard. OEM too long wait, so probably Meteor landing here next week. This botom end is not in condition for ported BB kit, some light mods will be enought. The overhaul will be realy throughout. But given the fact these saws are going for 2 times what I paid for this around here, I consider it not so bad deal.

 

[Frank Savage]

OK, so from curiosity and unsureness I´ve set up the crankshaft into big vice, made clamp for the micrometer and bolted this clamp to the vice plate, so there was no room for any movement or bending of anything (but the crank) at all. Plus I added a lever to be able to put about 80 lbs of pull/pressure onto the conrod. The new measurement revealed some 0,0011" or 0,035mm up-down play.
Is it OK here as a compensation for thermal expansion, or is it right on the edge to be shot?

This is not first saw I´m rebuilding, but a first one where I´m such unsure about the bottom end condition Thanks