is there a "better" stock carb for the 372 series?

[Derf]

There may have been some Tillotson carbs (made in Ireland) used back in the 2-series/transition to 3-series huskies, but Husqvarna hasn't used them on many saws in a long time.

The 371/372XP pre-EPA came with a Walbro HD-6B (Japan). The 372xp EPA came with a Walbro HD12B (likely what you have). The 372XP X-torq came with a Walbro RWJ-4. The advantage of the RWJ-4 is that the Venturi is larger than the HD12B and the theory is it flows more air which would match increased fuel delivery which could be better harnessed for a ported saw. [Keep in mind, on a x-torq saw, although the carb's venturi is larger, only half the area is devoted to "charge" flow (air+fuel) for the saw. There is a divider in the air filter holder (air horn) and boot to divide the air flow so half goes to the strato ports to flush out exhaust gasses with clean air (no fuel). ]

Downsides are that the RWJ4 bolt pattern is clocked from the pre-EPA 9'oclock/3'oclock to 4/10oclock on the x-torq. To get it to work you need to use the x-torq blue choke lever, the x-torq air filter holder, and x-torq boot between the carb and cylinder. The boot is rotated so the bolt holes line up.

Interestingly, the Dolmar Ps7900 (80cc saw) came with a Zama C3M carb (China). Although it's made in China, Stihl bought them. This particular model carb is the same carb that came on Husqvarna 365 specials (65cc saw), and has a smaller Venturi than the 372's HD12B. One might falsely assume that because it has a smaller carb Venturi it cannot handle the air/fuel delivery requirements of a 70cc+/ported saw. [Recall, the x-torq saw was actually only getting half the airflow of its carb, so Venturi size alone is not the b-all-end-all design spec to chase.]

@Poleman and @Terry Syd experimented with these Zama carbs because they have independent jetting passages (circuits), unlike the Walbro, which allows using needle drills to open up specific jet holes to balance/flow more fuel for a better tune for ported saws.

I have a Zama C3M on my 372XPW (75cc/ported) that was worked over by Poleman and it performs better than the stock HD12B. Faster acceleration, higher RPM in the cut, and faster cut times. I posted a video to prove it in the Chinese 372 thread.

https://r.tapatalk.com/shareLink?sh...orum.com/index.php?posts/512566/&share_type=t

Going to a 385/390XP carb is following more of the same theory behind going to the x-torq carb. Just an even larger Venturi.

 

[concretegrazer]

and x-torq boot between the carb and cylinder.

That doesn't fit.

Going to a 385/390XP carb is following more of the same theory behind going to the x-torq carb. Just an even larger Venturi.

I thought 390 venturi was smaller than the xt.

 

[Derf]

I thought 390 venturi was smaller than the xt.

Perhaps you are right.
Zama C3M Venturi : 17mm
HD6B Venturi : 16.67mm
HD12B Venturi : 17.46mm
RWJ-4 Venturi : 19.05mm
WJ-118 Venturi : 17.46mm


So, it leads to an interesting question :
Does a ported 70cc saw "need" a bigger carb venturi like the RWJ4? Or does it just need better/larger jetting?

If a 90cc saw can get away with a smaller venturi, then choosing a carb based on venturi size alone is a poor determinant.

I think the ported 70cc saws can benefit from increased fuel delivery. There are two ways to get that : use a carb that was designed to provide more fuel with the stock jets, or drill the jets to provide more fuel.

The Walbro carbs have combined fuel circuits so drilling one jet affects fuel delivery of other jets. So it isn't a good candidate to modify.

But, the 372x-torq and 390 carbs obviously flow more fuel, they just require adaptation to mount them properly.

 

[ken morgan]

Yeah i have been chatting poleman up here since I posted this I think if I can find a rebuildable Zama from a 365 but he indicated I needed to find a ZAMA CL 8 so I am on a quest. I will not be porting the Chusqvarna just a gasket delete and a muffler mod for the time being, but if I am gong to mod from stock i want the most out of what I plan on doing.

Anybody got a spare CL8 sitting around for sale?

 

[mdavlee]

Tillotson 296 and 298 were on 385/390 and 395.

 

[huskyboy]

Tillotson 296 and 298 were on 385/390 and 395.

I like them the best .

 

[ken morgan]

I like them the best .

Tillotson 296 and 298 were on 385/390 and 395.

do these have dual jets or a single? how much modding do they need to fit the stock 372 configuration?

pole man was also suggesting another possible carb from a Dolmar the carb was a C3M model told meI should talk with FordF150 about getting one of those. any thoughts or suggesitons? does the dolmar work better? bolt up easier? or maybe one of these tillotson's or back to the zama? it appears that I have multiple options and it might just come down to which one I can get my hands on over here.

 

[mdavlee]

They need the boot rotated and maybe the xtorq elbow to keep the filter in the normal place

 

[Derf]

do these have dual jets or a single? how much modding do they need to fit the stock 372 configuration?

pole man was also suggesting another possible carb from a Dolmar the carb was a C3M model told me I should talk with FordF150 about getting one of those. any thoughts or suggesitons? does the dolmar work better? bolt up easier? or maybe one of these tillotson's or back to the zama? it appears that I have multiple options and it might just come down to which one I can get my hands on over here.

All carbs have multiple jets, each adds more jets feeding the airstream as the throttle plate opens. However, the Tillys and walbros have single jet circuits (passages below the jet holes) feeding all those jets. Some Zamas have have single jet passages, and some have two jet circuits, which allow for modification.
The dolmar saws, especially the 7900, but maybe others, came with a Zama C3M carb that had twin jets. Dolmar doesn't actually make a carb. The C3M is a direct bolt on for the 372xp. The Tilly and the Walbro RWJ-4 (372xp x-torq) require changing the choke lever, the carb boot, and the air filter elbow.

There are multiple options, yes. Whatever is easier to get is a good starting point.

 

[mdavlee]

Carb boot can stay. Just have to rotate to get the carb body level.

 

[malk315]

Tillotson 296 and 298 were on 385/390 and 395.

I think the 385 Mike built for me came with one of the above stock (it's Tillotson but I don't know which model, probably 296 my memory had faded since looking it up)
It is hands down one of the fastest accelerating saws I've run -- as good or better than my KS/HDA87 ported by Randy 262 which has impressive accel.

You blip the throttle on the 385 and the response is like a rabid junkyard rottweiler getting pinched in the ass

+1 on Tillotson if you can mate one to your ported 372.

 

[huskihl]

Carb boot can stay. Just have to rotate to get the carb body level.

Throttle cable long enough? I wasn't sure

 

[ken morgan]

All carbs have multiple jets, each adds more jets feeding the airstream as the throttle plate opens. However, the Tillys and walbros have single jet circuits (passages below the jet holes) feeding all those jets. Some Zamas have have single jet passages, and some have two jet circuits, which allow for modification.
The dolmar saws, especially the 7900, but maybe others, came with a Zama C3M carb that had twin jets. Dolmar doesn't actually make a carb. The C3M is a direct bolt on for the 372xp. The Tilly and the Walbro RWJ-4 (372xp x-torq) require changing the choke lever, the carb boot, and the air filter elbow.

There are multiple options, yes. Whatever is easier to get is a good starting point.

Sorry, I probably could have worded that better, I should have been a bit more specific, most carbs that I deal with (webers) have a air jet, a fuel jet, an emulsion tube, and an idle circuit jet. (change actual jet to adjust fuel mixtures)

I will be ordering from whomever I can get to ship to me (overseas military base) so that narrows the field a lot as a lot of the larger online stores will not even talk to you once they find out you are at a military base

I am guessing that the chainsaw carb is vastly simpler in design (no float bowl, so no emulsion tube) and would have a high speed and a low speed circuit with needle valves used as the means of adjusting the jet orfice size for mixture purposes ( high and low adjustments) but that the actual jet itself might be fixed and there fore non replaceable for performance purposes (could possibly drill out though)

while knowledgeable about the aforementioned weber carbs the chainsaw is just my best guess. that being said does the C3M offer a performance advantage over the walbro?

Possible options that I thought of would be smaller venturi which gives better low rpm performance (velocity) but chokes it out on the top, or better tip in (low speed to high speed transition circuit), or better high end: larger venturi, larger jets (poorer low end performance along with tip in issues) not knowing these small carbs at all makes me ask these questions. i know for a fact that I will do a base gasket delete and a muffler mod as these are easy no brainers, and to be honest, chances are I will try porting the spare OEM cylinder after I have hacked on the chinese one and played around with the port timing to see the difference between the two. with that in mind will the C3M give me an advantage or should I just stick to the walbro?

 

[ken morgan]

should have read closer prior to typing the above.. so the C3M having separate fuel jets for the high and low circuits allows you to drill out the hi circuit for more fuel, without affecting the low speed circuit,hence your tip in (throttle response) and low speed air fuel ratio??

 

[Dub11]

Sorry, I probably could have worded that better, I should have been a bit more specific, most carbs that I deal with (webers) have a air jet, a fuel jet, an emulsion tube, and an idle circuit jet. (change actual jet to adjust fuel mixtures)

I will be ordering from whomever I can get to ship to me (overseas military base) so that narrows the field a lot as a lot of the larger online stores will not even talk to you once they find out you are at a military base

I am guessing that the chainsaw carb is vastly simpler in design (no float bowl, so no emulsion tube) and would have a high speed and a low speed circuit with needle valves used as the means of adjusting the jet orfice size for mixture purposes ( high and low adjustments) but that the actual jet itself might be fixed and there fore non replaceable for performance purposes (could possibly drill out though)

while knowledgeable about the aforementioned weber carbs the chainsaw is just my best guess. that being said does the C3M offer a performance advantage over the walbro?

Possible options that I thought of would be smaller venturi which gives better low rpm performance (velocity) but chokes it out on the top, or better tip in (low speed to high speed transition circuit), or better high end: larger venturi, larger jets (poorer low end performance along with tip in issues) not knowing these small carbs at all makes me ask these questions. i know for a fact that I will do a base gasket delete and a muffler mod as these are easy no brainers, and to be honest, chances are I will try porting the spare OEM cylinder after I have hacked on the chinese one and played around with the port timing to see the difference between the two. with that in mind will the C3M give me an advantage or should I just stick to the walbro?

Wait your say a US company won't mail you something to a over seas service man on a US base? Thats *f-worded up!

 

[ken morgan]

Wait your say a US company won't mail you something to a over seas service man on a US base? Thats *frenched up!

I guess I should explain this, I am no longer active duty, retired and working on the local base to stay out of trouble it also gives me access to the military postal system.

the actual problem is generally not with the companies (generally) it boils down to they do not use USPS only stuff like fed ex, or UPS. this being the case their is a bunch of customs forms and crap that needs filling out, which they instantly shy away from. if you mail via USPS to a military base then there is only one form, and its quite simple. its called a customs form but in reality its a notice to the local country you are staioned in to let them know its import tax exempt. you list what it is, its value and its insured amount. (this keeps idiots inline from smuggling countraband over) (weed etc. I have seen it all over the time I spent in the Marines (currently working as a civilian on the base after I retired).

Now I did have one well known (at least on arborist site) company that flat out refused to even consider dealing with me simply because I was on a base. I assume that dealer has his reasons ? even after i explained that he could legally mail it to me he was like nopestarted making excuses about mailing husky parts and I was like OK whatever, your loss. picked up my cylinder and piston from an ebay seller in the orginal husky packaging so his (vendor on AS) loss, my gain.

some of the dealers will ship to my stateside address, and then I use a freight forwarder, though it adds a minimum of $30 handling charge + the actual USPS cost + insurance per package so I only use it for expensive stuff that i absolutely need ... sofar jacks small engines, patano's and a few others have willingly shipped direct via USPS though i think one fo the companies adds an extra $5.00 for the post office run. (absolutely no problems with that, free market is free market and$5 is cheaper than the freight forwarder.

 

[Dub11]

I guess I should explain this, I am no longer active duty, retired and working on the local base to stay out of trouble it also gives me access to the military postal system.

the actual problem is generally not with the companies (generally) it boils down to they do not use USPS only stuff like fed ex, or UPS. this being the case their is a bunch of customs forms and crap that needs filling out, which they instantly shy away from. if you mail via USPS to a military base then there is only one form, and its quite simple. its called a customs form but in reality its a notice to the local country you are staioned in to let them know its import tax exempt. you list what it is, its value and its insured amount. (this keeps idiots inline from smuggling countraband over) (weed etc. I have seen it all over the time I spent in the Marines (currently working as a civilian on the base after I retired).

Now I did have one well known (at least on arborist site) company that flat out refused to even consider dealing with me simply because I was on a base. I assume that dealer has his reasons ? even after i explained that he could legally mail it to me he was like nopestarted making excuses about mailing husky parts and I was like OK whatever, your loss. picked up my cylinder and piston from an ebay seller in the orginal husky packaging so his (vendor on AS) loss, my gain.

some of the dealers will ship to my stateside address, and then I use a freight forwarder, though it adds a minimum of $30 handling charge + the actual USPS cost + insurance per package so I only use it for expensive stuff that i absolutely need ... sofar jacks small engines, patano's and a few others have willingly shipped direct via USPS though i think one fo the companies adds an extra $5.00 for the post office run. (absolutely no problems with that, free market is free market and$5 is cheaper than the freight forwarder.

Thank you for your service! Active duty or not still shouldn't matter IMHO! If you find something here and need it there just ship it to me and I'll mail it to ya. I've done it before through USPS and drive by them daily on my way to work.

 

[ken morgan]

I appreciate that, as a retiree we get base access regardless, and we can mail from the post office on base, just not receive. (no assigned command) being that I work on base I have a command so I get to use the post office going both ways

what I really ask of you though is that when you see some young man or women in uniform just give them your thanks, (Yes even the Chair Force)(Sorry had to ) the youngsters don't get that often enough anymore....a little positive reinforcement goes a long ways. thanks!

 

[Czed]

Amazon 55.00 free ship
C3m i really like the one poleman modded for me.

 

[Dub11]

I appreciate that, as a retiree we get base access regardless, and we can mail from the post office on base, just not receive. (no assigned command) being that I work on base I have a command so I get to use the post office going both ways

what I really ask of you though is that when you see some young man or women in uniform just give them your thanks, (Yes even the Chair Force)(Sorry had to ) the youngsters don't get that often enough anymore....a little positive reinforcement goes a long ways. thanks!

I do thank everyone of them I see. Both grandpa's and FIL in the army 2 uncles and 3 cousins in the Marines and 2 more cousins in the Army.