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372XP X-Torq Modding

Started by XP_Slinger, December 28, 2015, 08:16:01 AM

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RIDE-RED 350r

The OP is my brother and he and I did our 372's yesterday in his shop. Mine is the 75cc XPW and of course his is the XT...

With his top end off, I really don't see how this is a strato cylinder. It does not have the second butterfly along the carb that specifically feeds strato ports as I have come to understand them. What seems more in line to the XT 372 cylinder is that it has a 2-stage intake cycle. There is a small, single intake port in the customary location, and then there are the additional 2 intake ports about the same size as the transfers. Those "secondary" intake ports are being fed by the carb along with the main intake.

Am I missing something here that makes this a strato cylinder?? It is my understanding through learning here and other forums that the strato cylinders have separate fresh air ports that are isolated from the main fuel/air intake port that is regulated by a separate butterfly. This XT cylinder has none of those components or characteristics.

Edited to add: I am learning fast through the generous sharing of experience and wisdom here, but by no means do I claim to be the expert. Ready to stand corrected if I am incorrect in my assertion.
Swedish, you know, like the chef.

weimedog

No.. you are dead on. Nothing like the 562's or even the old 455's.  Just I was able to get more results with a tweaked 372 cylinder, or even the 52mm AM cylinders tweaked per amount of time spent with my knowledge set and limitations. And with the XPW... they have goofy transfers but even so, just getting the squish right and a simple muffler mod made a noticeable difference. So I have to defer to others for x-torq knowledge rather than re-invent that wheel. Only so much time! There are two guys who have spent time there. One "Terry Syd" has posted on the "strato" subject. The other is over at another site on specifics to the X-torq.

Maybe you can do some research and add to the collective knowledge here?? Would be nice to see someone focus on those X-torq cylinders.
Husqvarna 365sp/372xpw Blend, Jonsered 2171 51.4mm XPW build,562xp HTSS, 560 HTSS, 272XP, 61/272XP, 555, 257, 242, 238, Homelite S-XL 925, XP-1020A, Super XL (Dad's saw); Jonsered 2094, Three 920's, CS-2172, Solo 603; 3 Huztl MS660's (2 54mm and 1 56mm)

XP_Slinger

I didn't cut the cylinder for the exact reasons you stated...skirt support, piston port function and finally X-torque flow alteration.  The bottom of the cylinder has a very unique cut as compared to a traditional 372.  That alone made me pause I think that it may not be wise to grind on a prayer.
346XP/NE
357XP...ported by MeDremel
372XP/XT...ported by A. Burr
Homelite (Solo) 340

I'd rather be in the woods than on this computer.

weimedog

Quote from: XP_Slinger on January 02, 2016, 12:35:13 PM
I didn't cut the cylinder for the exact reasons you stated...skirt support, piston port function and finally X-torque flow alteration.  The bottom of the cylinder has a very unique cut as compared to a traditional 372.  That alone made me pause I think that it may not be wise to grind on a prayer.

So now we have three folks (u me and red) interested in these things .. maybe we should put some time into them.
Husqvarna 365sp/372xpw Blend, Jonsered 2171 51.4mm XPW build,562xp HTSS, 560 HTSS, 272XP, 61/272XP, 555, 257, 242, 238, Homelite S-XL 925, XP-1020A, Super XL (Dad's saw); Jonsered 2094, Three 920's, CS-2172, Solo 603; 3 Huztl MS660's (2 54mm and 1 56mm)

XP_Slinger



So now we have three folks (u me and red) interested in these things .. maybe we should put some time into them.
[/quote]

Sounds like a plan.
346XP/NE
357XP...ported by MeDremel
372XP/XT...ported by A. Burr
Homelite (Solo) 340

I'd rather be in the woods than on this computer.

weimedog

Quote from: RIDE-RED 350r on January 02, 2016, 11:50:41 AM
Ready to stand corrected if I am incorrect in my assertion.

Well Red....I have ONE assertion.. That is that since Eli Tomac flew away to Kawasaki...

The "Wing" doesn't have a "Prayer" this year in Super Cross... :)
Husqvarna 365sp/372xpw Blend, Jonsered 2171 51.4mm XPW build,562xp HTSS, 560 HTSS, 272XP, 61/272XP, 555, 257, 242, 238, Homelite S-XL 925, XP-1020A, Super XL (Dad's saw); Jonsered 2094, Three 920's, CS-2172, Solo 603; 3 Huztl MS660's (2 54mm and 1 56mm)

49er

Quote from: weimedog on January 02, 2016, 12:42:05 PM


So now we have three folks (u me and red) interested in these things .. maybe we should put some time into them.

Hey, count me in I have a 365 I plan on doing more mods to.
Husqvarna EC390 365xt
Jonsered 2188 2165 2260 2253 70e
Redmax GZ4000

49er

Quote from: RIDE-RED 350r on January 02, 2016, 11:50:41 AM
The OP is my brother and he and I did our 372's yesterday in his shop. Mine is the 75cc XPW and of course his is the XT...

With his top end off, I really don't see how this is a strato cylinder. It does not have the second butterfly along the carb that specifically feeds strato ports as I have come to understand them. What seems more in line to the XT 372 cylinder is that it has a 2-stage intake cycle. There is a small, single intake port in the customary location, and then there are the additional 2 intake ports about the same size as the transfers. Those "secondary" intake ports are being fed by the carb along with the main intake.

Am I missing something here that makes this a strato cylinder?? It is my understanding through learning here and other forums that the strato cylinders have separate fresh air ports that are isolated from the main fuel/air intake port that is regulated by a separate butterfly. This XT cylinder has none of those components or characteristics.

Edited to add: I am learning fast through the generous sharing of experience and wisdom here, but by no means do I claim to be the expert. Ready to stand corrected if I am incorrect in my assertion.

As far as the xt being a "strato," it is. It just has two paths through a single throat. The intake that has fuel air mix is relatively small but add the strato ports and the intake path is huge. The theory is get both sources of air into the cylinder where it is mixed together on the compression stroke. Very large potential for performance here.
Terry Sid posted a great thread on this in another location. The only experienced porter that has taken a shine to the 372xt I know of is ehp. Other porters are unenthusiastic at best. IMO.
Husqvarna EC390 365xt
Jonsered 2188 2165 2260 2253 70e
Redmax GZ4000

weimedog

I think we should do first a Upstate New York GTG/Build off of 356/372 X-torqs this winter or spring time... all three of us, (Maybe Spike60 makes 4?). Do another one either late in the year or early next year with what we learned by doing and invite a few more if there is interest. Maybe getting a few involved we can develop a good solid build that's fun to run and others can replicate. This stuff isn't rocket science... but it does  take time and understanding of fundamentals to make it a worth while endeavor.
Husqvarna 365sp/372xpw Blend, Jonsered 2171 51.4mm XPW build,562xp HTSS, 560 HTSS, 272XP, 61/272XP, 555, 257, 242, 238, Homelite S-XL 925, XP-1020A, Super XL (Dad's saw); Jonsered 2094, Three 920's, CS-2172, Solo 603; 3 Huztl MS660's (2 54mm and 1 56mm)

RIDE-RED 350r

Swedish, you know, like the chef.

XP_Slinger

I wonder why there isn't enthusiasm for x-torqs considering mine runs no different than my brothers XPW 75cc stock to stock.  I would think the porting crowd would be all over a saw that runs that strong in stock trim.  Strange.  Here's hoping the pro's take another look at them.  There's a lot of us running them.
346XP/NE
357XP...ported by MeDremel
372XP/XT...ported by A. Burr
Homelite (Solo) 340

I'd rather be in the woods than on this computer.

weimedog

I can speculate. (But then have to go to work..:( ) It has to do with what you have both the tooling and experience for. A lot of what you do with the "conventional" cylinders translates from one to the next. So you can stay in your skill set/power curve work on them. It takes a lot of time and research to develop a build concept that's something your willing to put out in the market place. That combined with the onslaught of new Stilh and Husqvarna Strato saws like the 562/550 MS661/461 etc. the band width of those with the shops has limitations. Add that all up? 372xt's has less support than other saws. So ... maybe it would make sense to dive in and see what's available. As I mentioned, there seems to be more aftermarket support for them now. I have a blown up one on the bench but plan to just do my standard routine which is: ... muffler mod, no base gasket, re-sealed transfer caps, a intake boot (the latest of the four options!) ,cut a bit off the fin by the plug wire etc. It's getting "Nachi's" for bearings and new case seals as well.
Husqvarna 365sp/372xpw Blend, Jonsered 2171 51.4mm XPW build,562xp HTSS, 560 HTSS, 272XP, 61/272XP, 555, 257, 242, 238, Homelite S-XL 925, XP-1020A, Super XL (Dad's saw); Jonsered 2094, Three 920's, CS-2172, Solo 603; 3 Huztl MS660's (2 54mm and 1 56mm)

XP_Slinger

I was hoping Spike60 would chime in on this thread at some point, he seems to be one of the few that has any interest in the x-torq saws.  I would love to be somehow involved in a build off.  I may not bring experience to the table with regard to porting but I would be happy to help in any way I can.  I'm sure my brother Ride Red 350R would lend a hand as well.   Please keep me posted.
346XP/NE
357XP...ported by MeDremel
372XP/XT...ported by A. Burr
Homelite (Solo) 340

I'd rather be in the woods than on this computer.

CR888

The strato design is what we have now on modern saws, builders I suppose are used to older prooven designs and methods. The xt has some good things going for it in its design but many find the xp easier to get the numbers they want with less work involved getting there. We don't have the xt in OZ, unfortunately we can only buy XP'S. (smiley face)

RIDE-RED 350r

I would certainly be in for some shop time.

Just not sure I can muster the coin for another saw to experiment with... And I don't think I can part with my XPW to trade in on an XT.

I am in the beginning stages of skimming some $$$ out of the family budget to piece a 394 together.. I have a dirty cylinder..that's it so far! LOL!
Swedish, you know, like the chef.

Spike60

Quote from: RIDE-RED 350r on January 02, 2016, 08:31:25 PM
And I don't think I can part with my XPW to trade in on an XT.

Lordy no, don't do that! The XPW is still the better saw.

But count me in for the GTG; sounds like fun. But we aren't going to borrow the "build off" term from those other guys. Those things are wrought with a lot of chest beating and arguing. We're going to call this a "tech seminar" GTG. Focus for this one being the XT saws. This what Walter and I do when we get together. Share and compare; put our heads together and build some saws. Be great to have some new minds adding to the conversation. We could focus on other chassis in the future.

That cylinder skirt on the XT jug cannot be removed like we do on the originals to open up the access to the transfers. It will expose the clean air channel cut in the piston. I of course learned that by ruining a cylinder.  :)  No biggie, cause it was a used one. And that's why Walt and I like used and aftermarket stuff for this learning process!

I have a 2166 that has been my test mule for this series. May have the raw materials for an orange version as well.

Be glad to have some of you guys join us and put some energy into these XT's. The originals get all the attention, and in a year or so all of the attention will be on the 572's. But the XT's are still selling in large numbers and will continue to be popular for a long time.
Husqvarna-Jonsered
Ashokan Turf and Timber
845-657-6395

49er

I never been to New York. It would be a fun trip. :)
Husqvarna EC390 365xt
Jonsered 2188 2165 2260 2253 70e
Redmax GZ4000

weimedog

Especially with that machine in your avatar!
Husqvarna 365sp/372xpw Blend, Jonsered 2171 51.4mm XPW build,562xp HTSS, 560 HTSS, 272XP, 61/272XP, 555, 257, 242, 238, Homelite S-XL 925, XP-1020A, Super XL (Dad's saw); Jonsered 2094, Three 920's, CS-2172, Solo 603; 3 Huztl MS660's (2 54mm and 1 56mm)

ehp

the XT design is pretty simple to figure out , well seems pretty easy to me . Yes you grind the bottom of the cylinder to remove restriction for the transfers ,but watch you donot grind to much towards the doors on the cylinder or you will have a big air leak , next end up at around 180 psi of compression, any more than that your not helping the saw , your hurting it . open up the strato in the intake so it gets fuel/air as well not just air , its not hard, you need to grind the plastic part that bolts to the carb that holds the air filter , take that bridge out so its like the older 372 style, next grind the rubber boot that goes between the cylinder and carb so its also just like the older 372 style . Yes you need to raised both the transfer and ext port and these engines are not to fussy , if you get a touch to high on your porting they still will pull good . you can widen the ext port lots . You can increase the flywheel timing lots as well . Will these beat the older 372/375 in 8 by 8 cookie cutting , most times no but there still strong , will they out cut the 372/375 in big hardwood , without a question , the XT's have a lot of torque and can handle cut after cut after cut . I use XT's everyday and cut good size big hardwood . I got a 390 and it only sees the landing some days , just way to heavier and not as nice to run in my books . Problem I see with some guys is they donot take a engine a part and figure it out , every design needs different mods and porting numbers , what works in a older 372 will not work on a XT just like what works on a 7900 will not work on a 372

Spike60

Thanks for sharing Ed. You're one of the few guys who have figured out the XT's. I agree that each saw needs it's own recipe. Do you also get rid of the divider in the carb along with the intake boot and filter holder? I'm going to try some of your ideas.  :)
Husqvarna-Jonsered
Ashokan Turf and Timber
845-657-6395

XP_Slinger

Quote from: Spike60 on January 03, 2016, 10:24:26 AM
Quote from: RIDE-RED 350r on January 02, 2016, 08:31:25 PM
And I don't think I can part with my XPW to trade in on an XT.

Lordy no, don't do that! The XPW is still the better saw.

But count me in for the GTG; sounds like fun. But we aren't going to borrow the "build off" term from those other guys. Those things are wrought with a lot of chest beating and arguing. We're going to call this a "tech seminar" GTG. Focus for this one being the XT saws. This what Walter and I do when we get together. Share and compare; put our heads together and build some saws. Be great to have some new minds adding to the conversation. We could focus on other chassis in the future.

That cylinder skirt on the XT jug cannot be removed like we do on the originals to open up the access to the transfers. It will expose the clean air channel cut in the piston. I of course learned that by ruining a cylinder.  :)  No biggie, cause it was a used one. And that's why Walt and I like used and aftermarket stuff for this learning process!

I have a 2166 that has been my test mule for this series. May have the raw materials for an orange version as well.

Be glad to have some of you guys join us and put some energy into these XT's. The originals get all the attention, and in a year or so all of the attention will be on the 572's. But the XT's are still selling in large numbers and will continue to be popular for a long time.

A tech seminar is exactly what I would enjoy.  Good people, good food, cold drinks and chainsaws.  Does it get any better? 
346XP/NE
357XP...ported by MeDremel
372XP/XT...ported by A. Burr
Homelite (Solo) 340

I'd rather be in the woods than on this computer.

RIDE-RED 350r

I would love to get together for a tech seminar!

Maybe instead of having to source a whole other 372xt saw, those of us who are planning to get together could each get an aftermarket XT cylinder to bring with us??

I remember you showing in one of your vids Spike that the XT cylinder does not seat onto the traditional XP/XWP case without some modification due to there being more cylinder protrusion into the case... Having said that, I would be willing to bring my XPW to use as an experimental bottom end for the XT cylinder. Unless of course using the XT cylinder on my XPW bottom end would render the testing less than accurate due to the fact my XPW uses a traditional carb and intake??? Obviously in my case I would have to get the std size 372 piston as my XPW has a slightly larger bore...

BTW, I did some work on my XPW cylinder the other day while XP_Slinger was doing his XT...

I matched the transfers to the base gasket, opened up the lower transfers (wow that exhaust side had alot of material with that hump!), beveled and blended the transfer partitions, cut the cylinder skirts down to 2.500" as measured from the squish band on both sides, deleted the base gasket, and modded the muffler. I was very pleased with the end results.  ;D

Having some trouble figuring out how to post pics... otherwise I would show you what I did..
Swedish, you know, like the chef.

XP_Slinger

No need to tear into your XPW for a testing bottom end, since I have an X-torq we could use mine.  Can't wait for this gathering to happen.
346XP/NE
357XP...ported by MeDremel
372XP/XT...ported by A. Burr
Homelite (Solo) 340

I'd rather be in the woods than on this computer.

XP_Slinger

Quote from: ehp on January 03, 2016, 06:41:40 PM
the XT design is pretty simple to figure out , well seems pretty easy to me . Yes you grind the bottom of the cylinder to remove restriction for the transfers ,but watch you donot grind to much towards the doors on the cylinder or you will have a big air leak , next end up at around 180 psi of compression, any more than that your not helping the saw , your hurting it . open up the strato in the intake so it gets fuel/air as well not just air , its not hard, you need to grind the plastic part that bolts to the carb that holds the air filter , take that bridge out so its like the older 372 style, next grind the rubber boot that goes between the cylinder and carb so its also just like the older 372 style . Yes you need to raised both the transfer and ext port and these engines are not to fussy , if you get a touch to high on your porting they still will pull good . you can widen the ext port lots . You can increase the flywheel timing lots as well . Will these beat the older 372/375 in 8 by 8 cookie cutting , most times no but there still strong , will they out cut the 372/375 in big hardwood , without a question , the XT's have a lot of torque and can handle cut after cut after cut . I use XT's everyday and cut good size big hardwood . I got a 390 and it only sees the landing some days , just way to heavier and not as nice to run in my books . Problem I see with some guys is they donot take a engine a part and figure it out , every design needs different mods and porting numbers , what works in a older 372 will not work on a XT just like what works on a 7900 will not work on a 372

Excellent info, thanks for sharing.  I've been admiring your work on youtube...impressive.
346XP/NE
357XP...ported by MeDremel
372XP/XT...ported by A. Burr
Homelite (Solo) 340

I'd rather be in the woods than on this computer.

CR888

I am yet to read a post from spike60 that has not been positive and insightful. Always good when he joins the party. Few guys have the knack to communicate and come off well in what they post whether they agree or disagree with what someone has said, he is definitely one of those guys. You gotta sell yourself before you can sell a product/service well, he has certainly mastered this process.

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