Need help with 372x torq

[Cas101326]

So I got a 18 model 372 x torq in a box from a dealership on a trade, story was it was purchased from them, had issues they put piston on it, then came back put top end on it, and came back again with toasted crank so they replaced it. So I slowly rounded up everything I needed to do full rebuild, including a used OEM crank I purchased on eBay. New Nachi crank bearings, meteor piston kit, put it all together, carb seemed to look fine, removed limiters, saw crunk fine, sounds like it runs strong,probably run a tank through it just idling, then when I started trying to tune, I never could get it to lean up, and most of the time if you hit the throttle it’s super slow to respond, then when you let off most of the time it’s like it back fires and dies…been reading on here and have been pointed towards coil and timing issues. I noticed when I was putting crank in, that it was exactly the same, but the part number was different. I’ve looked through everything I’ve got and can’t find the part number anywhere, but I know it was different than the one I pulled out, and I know the flywheel was original to the saw. I’ve checked air gap, got a good spark, so I was wondering if anyone might think it’s possible that the crank I installed has a different key timing than the one I pulled out, or if all that will fit will be the same, and if that’s possible that it is different, the best way to check and see. I do still have the original crank. And there’s the thought that maybe something’s up with the carb, but like I said it’s an 18 model and it looks like it’s in great shape, saw doesn’t look like it had much run time at all.I’m so anxious to run this saw and this is a big disappointment and I’ve been off and on dealing with it for several weeks trying to patiently work it out

 

[lostone]

So what have you done with the carb? rebuild/cleaned or ran it how you got it? Backfire is a timing issue, what color is the coil, blue?

 

[Cas101326]

I cleaned it, both diaphrams look good, carb was clean inside, so I didn’t kit it. Yes it’s a blue coil, that’s limited right? I had a black one on 365 sp project I acquired, put it in briefly but it doesn’t appear to fire so unless one will work off of a 570 or 357 or 268, all I have is the blue one for now

 

[lostone]

I was looking to see if someone changed it out, leave the blue on it.
Spark plug? have you put a new one in? getting a good spark in atmospheric pressure and getting a good spark under compression is two different things. Trying to rule things out is why I am asking.

 

[lostone]

Also after installing new bearings, seals, crank, piston and cyldinder did you do a pressure vac test?

 

[Cas101326]

No but I can put a new plug in it. I didn’t do pressure vac test, I don’t have the stuff to do it and don’t fully understand the process, but can try to get the tools to do it if u can give me some good directions. Could that be causing it?

 

[Backstage]

Won’t lean… Too much fuel or too little air. Check carb needle lever height. How’s air filter, muffler?

 

[huskihl]

Not being able to lean the carburetor out enough is usually from a stiff diaphragm holding the needle lever down or a chunk in the needle seat not allowing it to seal

 

[Cas101326]

And it causes it to pop and backfire and die??

 

[Backstage]

No but I can put a new plug in it. I didn’t do pressure vac test, I don’t have the stuff to do it and don’t fully understand the process, but can try to get the tools to do it if u can give me some good directions. Could that be causing it?

Get part numbers from parts diagrams at shop.husqvarna.com

Pressure testing is simple. You can do it with a bit of rubber sheet, a good spare purge bulb, and fuel line. Cut the rubber sheet in a strip as wide as the port openings on both the carb and muffler side. A slight taper is useful to get the width just right. put it between muffler/carb and cylinder, and use the muffler/carb as a clamp. Be sure your spark/decomp ports are sealed.

Attach fuel line to your impulse barb. Use your purge bulb to apply pressure or vac. Let it sit for a minute. Removing the purge valve will “FSSSS” pressure if it was holding. Of course, you’ll get a disappointing lack of noise if it leaked. You can use liquid to find exactly where a leak is.

 

[Gord404]

Get part numbers from parts diagrams at shop.husqvarna.com

Pressure testing is simple. You can do it with a bit of rubber sheet, a good spare purge bulb, and fuel line. Cut the rubber sheet in a strip as wide as the port openings on both the carb and muffler side. A slight taper is useful to get the width just right. put it between muffler/carb and cylinder, and use the muffler/carb as a clamp. Be sure your spark/decomp ports are sealed.

Attach fuel line to your impulse barb. Use your purge bulb to apply pressure or vac. Let it sit for a minute. Removing the purge valve will “FSSSS” pressure if it was holding. Of course, you’ll get a disappointing lack of noise if it leaked. You can use liquid to find exactly where a leak is.

Xtorq boots are a little more involved to block off than xp's because of the way they mount with all the divider and pins sticking out but can be done with an adapter, and an air leak usually causes them to over rev and be all over the place... sounds like carb or coil to me but a vac pressure test is always a good idea. Cranks for 372's are all basically the same timing etc.

 

[Woodslasher]

Coil gets my vote. My brother's 372 would run like a champ some of the time and the rest of the time it would smoke, sputter and run like crap. Since it had cut well over 100 cords of firewood by that point I rebuilt it figuring it was an air leak. There was absolutely no change and eventually it just died, a quick checked showed that it didn't have any spark so I swapped over the coil from my 372 and it fired right up and has run flawlessly ever since.

 

[Nitris223]

372 Xtorq saws need to be set with a tach also. Using the limited coil the saw can be leaned out and still sound like it's 4 stroking at wide open throttle. That is because of the limited coil. I believe the max rpm is 12,300 or 12,500. Been a while since I did mine. You can not tune a xtorq properly by ear.

 

[Cas101326]

Yes I have tach and haven’t got it above 8 or 9 but I can tell something’s not right so haven’t proceeded with tuning anymore, again like I said when you do get it to rev up and go to WOT when u let off or when you let off and start to give it more gas again, it pops and dies and sends smoke/vapors out of breather. Have took air filter off to no effect, adjusted metering lever height both set to specs as well as higher and lower, seems to be no real results, that’s why I’m so puzzled. Definitely no expert, and this is only my second saw to do bottom end rebuild, but never had this issue and never had an issue where I can’t seem to do anything to get any different results out of it. I guess I will try to get a new plug and a carb kit and see what that does, but all diaphragms look and feel like new, I’ve definitely seen way stiffer in saws that still run fine. I can try to get stuff to do pressure test, but when I first started up I sprayed around with carb cleaner, around flywheel, around clutch, around intake boot, never reved up or had any effect. May be end of this week before I get a kit and mess with it any but I will keep y’all updated. Definitely don’t wanna spend $100 on a new carb or new coil and it don’t fix my issue

 

[Woodslasher]

Here’s a good non-rev limited coil that you could try: It says it’s for a 350, but they work fine on 372’s as well.
https://store.chainsawr.com/collect...arna-350-chainsaw-ignition-coil-2-non-limited

 

[Cas101326]

So one from a 357 should work? I’ve got a 357 project as well as a j red 2153 I could rob one and if that fixes it then just get another one

 

[Woodslasher]

So one from a 357 should work? I’ve got a 357 project as well as a j red 2153 I could rob one and if that fixes it then just get another one

Yep, either should work.

 

[HumBurner]

372 Xtorq saws need to be set with a tach also. Using the limited coil the saw can be leaned out and still sound like it's 4 stroking at wide open throttle. That is because of the limited coil. I believe the max rpm is 12,300 or 12,500. Been a while since I did mine. You can not tune a xtorq properly by ear.

Sorry to say, but this statement doesn't make sense to me. Could you explain WHY it can't be tuned by ear or in the cut?

I just don't see how an rpm limiter/governor could affect the ability of the user to tune within that available band.


Thanks.

 

[Nitris223]

The XT limited coil is set for a lower rpm then the same coil that would be used on the 372xp model. I think the xt can be leaned out to 4 stroke but the rpm is actually past peak running rpm. It has something to do with the crank bearing load also from the heavier piston.
I forget where I read all the info. It was this site or the forestry forum.
It's out there .

 

[HumBurner]

The XT limited coil is set for a lower rpm then the same coil that would be used on the 372xp model. I think the xt can be leaned out to 4 stroke but the rpm is actually past peak running rpm. It has something to do with the crank bearing load also from the heavier piston.
I forget where I read all the info. It was this site or the forestry forum.
It's out there .

Thanks for clarifying. That gives me a slightly better grasp on the matter.