Hello, Noob needs help with 3 372xpw, all ported, all blown, one by me.

[nohandle]

So, my neighbor cuts wood for living down by springfield and he uses these 372s up in 2 years or so each. I asked him for a couple and he gave me a 262xp,272xp, that i have running and then 3 372xpws. The first one was a 2004 71cc cylinder that had been dropped off a truck or under a tree or something, it was missing most of it, However the cylinder was in excellent condition as was the piston. call it B.
The second saw was a 08 xpw with 75cc head and when i pulled it apart it had seazed the rings, one on each side of the piston. but the cylinder otherwise looked good. call it C
Then that week he blew up his 09 xpw 75cc. Heres where my bad behavior begins. call it A.

So i pulled the head off A and it looked like the first set of pictures. obvious slgn of detonation on the exhaust side of the piston and cylinder, NO scoring though. Intake is heavily scored on the piston but felt smooth to my fingers in the cylinder?

I installed the P/C of B onto A and got her fired up for about 15 seconds running rich and heard a little piston slapping for like 1 second, not detonation. and she died. Tore her down and the 71cc P/C now looks just like the 75cc that i just took off. Clean exhaust side, intake scored to hell.

Is this bad crank bearings? When i felt them in A they had what i felt was excessive lateral play but horizontal play was zero on the rod. I used my neighbors fuel in both, and it had tons of oil, nice and blue.

Well i'm wanting to rebuild the one with just frozen rings, C, Should i spend $99 on a oem piston 51.4mm or get the 52mm BB kit for $90? any opinions? i think it has solid bearings.

I have also considered separating the case and pulling the crank on B, heating it in the oven and pulling the main bearings. swapping into the case on A and rebuilding her too with a BB kit, would a meteor 71cc kit be better?

I'm thinking of running the kit for a bit, checking the squish, having it machined, porting it too at some point after the fact probably for both.

Again i really want to know why the piston/cylinder failed in this manner on the intake side? Also i am really looking on recommendations on the paths I've suggested for a resurrection. Thanks all.

 

[GASoline71]

Sounds like your neighbor needs to find a new line of work. Anybody that can smoke 3 saws in 2 years shouldn't be runnin' saws.

Gary

 

[nohandle]

Well 2 or 3 years per saw. He has 3 in the truck usually, runs a logging outfit right now. These are the saws that were not torn apart from parts robbery. When i asked about the life span he said that he needs the power for felling and he doesn't want to pack the weight for bigger saw, In his late 50's. So he runs rape aped 372s with a 32 inch bar and borrows bigger stuff from coworkers if needed. Word is he has a massive graveyard at his father in laws, and since i have gotten 5 Husky xps from him in the last 2 months and he wouldn't take any money i offered. I think he's a badass and should log FOREVER. Much love.

I really need help fixing saws not picking on or defending my charitable neighbor. Any input does help. Here are the rest of the photos i couldn't post yesterday. 5 pic limit?

I believe his dream is that i can start building the cylinders for his work saws. Again all ported and decked. And i will with enough practice and education.
:msp_biggrin:
Thanks in advance.

 

[nohandle]

last picture of C. The top ring was seated when i removed the cylinder. It snapped in two when i pulled it out of the piston. View attachment 185596

 

[nohandle]

again

 

[HILLBILLYREDNEC]

My thought of the day is do a complete over haul. Start by splittin the best lowerend and install new bearing and crank seal and build a a frankensten saw out of the parts pile you have.

 

[sunfish]

I'd put new pistons and rings in the good cylinders (if they are in fact good)
and fix the air leaks.

 

[sunfish]

Complete over haul is a very good idea.

BB kits for the ones that need new cylinders.

 

[mdavlee]

I would try to get an oem piston for the xpw topend that's still good. Do a vac/pressure test on it or put new bearings and seals in them and use that topend.

 

[nohandle]

Well this sounds supportive. I was leaning toward rebuilding the one that scarfs intakes in the manner described. Robbing bearings and crank/rod from the low miles exterior damage saw(a corner of the crankcase where the oil reserve is bye the dog mounts is cracked off ). New gasket set, piston pin bearing, oem piston set(might include bearing i'll check) in the cleanest pre-ported stock 51.4mm bore cylinder.

My other idea is to to take the saw that gave up the nice cylinder and rebuild it with a 71cc nwp kit, new piston bearing, fcast rings, and gasket set. Should i separate the case on this one for new case gasket? Should i just go BB?

I was planning on a $10 carb kit for both.

Is air leaking the likely culprit to intake scaring?
I also read it might be moisture in the intake charge? he showed me a saw one of his boys brought in last month that wouldnt pull. had a crank case full of water(i surmise left muffler up in a bucket mount with rain piston TDC how else?)

Anybody have experience heating the case to 400f and knocking the bearings in and out? This is the correct procedure yes?

 

[betterbuilt]

I think I'd splurge for new bearings. Seems like a lot of work just to have them fail down the road.

 

[GASoline71]

He sounds like the kid of cat that will lean a saw out for "more power". If he is one of them cats... it's hell on a saw. Gets 'em hot and then the seals and bearings will go too...

Those 372's should last a lot longer than that. Even havin' the snot beat out of them every day.

Gary

 

[parrisw]

Intake side scoring usually means lack of lube. Exhaust side scoring usually means its been run LEAN!

Those cylinders are ported I can see, maybe its not the best job and has hung a ring? Port curve not up to snuff? Lack of bevel?

 

[Dan_IN_MN]

.........Anybody have experience heating the case to 400f and knocking the bearings in and out? This is the correct procedure yes?

Since no one has answered this question I’ll give it a go….

Heating the empty case half to put a ‘cold’ bearing in works…..( I don’t recall the temp…I believe 400 is a bit hot) To get the bearings out of the case and off of the crank, there are tools made for that. Do a search for “case splitting” and you should get enough to keep you busy for a while.

Heating a case and crank to get the bearings out isn’t the way to go. Both the bearing and case will expand with the heat. Granted, I believe that the magnesium will probably expand more than the steel bearing race…. But the above mentioned case splitting tools are preferred.

Good luck with your saw rebuilding ventures!

OH.....welcome to AS!

 

[mdavlee]

You can make a case splitter with a piece of angle iron and a steering wheel puller by drilling a few hole in the angle to mount on the bar studs. After it comes off that side it tapped out easily on the other side. Then a socket sized to the outer race will get the bearing out of the case if it doesn't come out with the crank. I tapped the bearings onto the crank with a socket cold and then heated the case halves to 250 in the oven for about 15 minutes. Next time will be about 30 minues on the case.

 

[nohandle]

Thanks again, this stuff is super helpful, i'll make a splitter with my steering wheel puller . I have a welder too for cheating .

When i got the first couple saws i got shop manuals in pdf for 262/272 series saws, and 371/372 series saws. The manual says to heat the case to 200 degrees Celsius, (at first it just says 200 degrees, you gotta search for the Celsius or something like 395 degrees Fahrenheit, said press, i was planning on tapping them out and in with sockets or modified pipe depending on the diameter, and with the case separated no crank installed .

So if it was lean death it should have exhaust scoring, All three cylinders were ported, the 75cc both had fused rings, the 71 cc was good till i screwed it up. Only the 2009 xpw bottom end has done that cute intake scoring on two cylinders, one in less than 20 seconds of running and it wasn't lean.

However lean death would suggest crank seals with the bearings and then a air leak resulting in detonation and fast death . does this sound like what your saying. (that 20 seconds didn't exhibit that dirt bike high idle air leak sound)

I have been leaning, nuk nuk, toward the lean feeling but he said he doesn't tune them after he gets them built and he said premium fuel no ethanol/husky oil mix

The cylinder i blew up had the nicest port and the least knife edging of the cylinder bottoms of all three it did have odd almost ballooned intake side transfers, instead of what appears to be the consensus of rolling the intake side transfer port toward the intake.. he did say he only paid $150 for the deck and ports on his saws which makes me wonder, I think maybe shop in cottage grove, somethin grove.

All this stuff has got me thinking though thanks again. (also it would be stupid not to spend $40 for new crank bearings with what im planning. thanks)

 

[nohandle]

here's the odd transfer port on the cylinder i trashed. (2004 71cc)

Weird, i did a massive post right before this that didn't make it up.

I have shop manuals for the 371/372 series and it says 200 deg Celsius (396ish Fahrenheit) for the case sides and to press them, i was planning on a socket tap job myself.

So he said he doesn't tune them after they are built, and premium no ethanol fuel. However if the crank bearings go, theirs the potential air leak, then the detonation, and thus the death? Thanks for all the help

 

[Jacob J.]

The detonation can be from a variety of causes- poor fuel, incorrect type oil, air leak at some point in the system, excess carbon build-up. The best thing to do is diagnose the problems each individual saw has and correct those problems. New bearings and seals all around is a good idea and that way you'll be assured that you're starting out with a strong platform.

New fuel systems in each saw is a good idea as well.

 

[Gologit]

Is Zane back?

 

[Jacob J.]

The cylinder i blew up had the nicest port and the least knife edging of the cylinder bottoms of all three it did have odd almost ballooned intake side transfers, instead of what appears to be the consensus of rolling the intake side transfer port toward the intake.. he did say he only paid $150 for the deck and ports on his saws which makes me wonder, I think maybe shop in cottage grove, somethin grove.

If he had them done in Cottage Grove then it was likely at Larry Horner's shop. I bought a new 066 there in '93 and had it modified and the guy at the time (Scott) did a real good job on it. He's long gone now though. Danny Horner has been building some saws at that shop but I'm not sure if he's still there. It's been a couple years since I've been in. There was a retired log cutter out on Mosby Creek road that was building saws- I can't remember his name. Jack Wiggins or something like that. His sister-in-law was a music teacher at the high school for years.