converting a husqvarna 372xp xtorq to a big bore

[Ima Doher]

Let me start with I have always as with most of you done my own work with automotive, mowers, saws, whatever. I like the prices much better . I say that so nobody wastes their time with my post looking for some work. I have nothing against people looking for work but some of them won't answer any questions and seem a little put out when the person won't send them work and that just kind of derails the whole forum question and answer prospect. So for those looking for work! I salute you so don't be offended!

I have a project saw that is a husky 372xp xtorq 2012 is the year. I understand that the the year for the big bore kits that I see all over the place is from 2001 up to year 2011.
I also understand the kits are 52mm and sold from factory it came with a 50mm.
I'm told there is a 51.5 or 51.4 cylinder and jug that would work for the 372xp xtorq year 2012 and above but I think the price is more like 250 rather than 125 to 150 for these other kits I'm referring too.

What I don't understand is what would prevent me from installing the 52mm kits for 2001-2011 on the xtorq.
Someone said it was or may be the piston is different. But these kits come with a piston and cylinder already.
Someone mentioned the boot for the carb would need switched as well.
So can anyone tell me what other parts would need replaced?

And for that matter it seems swapping out the crank case with crank, case, jug and piston to a 372xp after market....does anyone know if this is a a simple swap out parts wise where I would only need say a new carb boot? I mean the crank, case, jug and piston are only 125 to 150 it's really a no brainer except for the details.

 

[RIDE-RED 350r]

You can put old style OEM 372, OEM XPW (75cc) or any 372 top end on an XT crank case... Can't put XT top end on pre-XT case though. The cylinder skirt protrusion is greater on the XT cylinder and therefore the case has deeper skirt reliefs to accommodate.

That said, I do know that the intake boot is quite a bit different on the XT compared to the pre-XT saws. But they can be gutted so you might be able to run the XT carb and boot on any pre-XT cylinder. The XT carb has a larger diameter venturi which may come in handy if you want to mod your new cylinder.

Personally, I would go with an OEM pre-XT or XPW top end kit over AM big bores. Quality is reported by many to be all over the map with some of the AM kits... Sometimes you get a good one, other times you might not.. But they offer a less costly solution so take your pick.

 

[Ima Doher]

Thats alot of good info, thanks for taking the time and sharing.

 

[Big_Wood]

to add, the intake boot is a no go and you must use the one from the OE along with parts like clamp and carb mount flange. you can use the XT carb IF you trim the intake boot so it can be rotated on the cylinder to angle the mounting holes correctly for a walbro WJ series carb or you can use a 390 intake boot.
i personally don't like the RWJ4. it's impressive cause it's big and that's all anyone sees. the venturi is 19.06mm nominally but the upper portion of the carb bore doesn't even have a venturi cast in so it's more like 23mm or something like that. it's a piece of **** and the only way i can get it to run the way i like on anything other then the 372 XT is the have a stupid long intake duration. people like it cause it's bolt on convenience but it doesn't buy them anything but negative work saw behavior. i have found that porting around a stock carb is much better for a work saw then porting to use a bigger carb. the HD12 from an OE runs a ported 372 just fine so unless you want a cookie cutter i would go with that carb. so anyways, if you did the mods to run the XT carb you could stick with the XT filter mount. if you swap to the HD12b carb then you will need the filter mount from the OE saw as well. choke levers are also different between the carbs.
other then that you should be good to go. i'm thinking of trying one of the higher quality nikisil big bore kits so see how they last. the farmertec big bore ran good but started peeling that cheap chrome plating within 120 tanks. pulled apart and cleaned it up so it still runs and on a firewood hack saw right now so we'll see how long before it shows back up here lol

 

[RIDE-RED 350r]

^^^Good info, I wasn't positive on some of those points^^^

But I do think that the reason for the larger ID of the XT carb is to allow it to feed it adequately with the entire intake tract divided all the way through the carb to feed clean air to the strato ports. I would infer that dividing the intake and carb with an OE sized carb might not adequately feed the unaltered XT setup.

 

[Big_Wood]

^^^Good info, I wasn't positive on some of those points^^^

But I do think that the reason for the larger ID of the XT carb is to allow it to feed it adequately with the entire intake tract divided all the way through the carb to feed clean air to the strato ports. I would infer that dividing the intake and carb with an OE sized carb might not adequately feed the unaltered XT setup.

i would never run a HD12B on an XT. that's just crazy talk. the XT 372's run best with the RWJ4. i've tried everything from WJ116 to a WJ69. thing about the RWJ like you say is it's designed the have 2 intake tracts separated. velocity in the lower track is gonna be much higher with the 2 devided then it would be on an old style saw with the carb devider still in place because you are deviding what vacuum the saw has amongst the 2 tracts making velocity in the lower tract poor which is what counts. i'v thoroughly tested the larger vs smaller carb thing. the RWJ4 is honestly one of the worst carbs anyone could put on an OE saw 372 or 390, at least with the way i port.

 

[Gord404]

Just want to clarify a few things dealing with taking a non xt cylinder and bolting it down to a xt crankcase, I have lots of non xt parts including boots carbs etc, can I do that or will there be any problems with swapping one for the other, in other words I just want to take the xt scored cylinder off and put a xp cylinder in it's place???