372XP/OE - Fix RWJ4 or Swap for 390XP Carb?

[qurotro]

Yes it is. It’s identical to an HDA199 (357xp). It has that black spacer on the diaphragm side. No vent hole in the cover.

It actually runs normally if you remove the spacer and use a regular cover with a vent hole. I own a 371K power head and tried. But that saw is stock so I dont know how it performs in moded saw. It just rusn and cuts like a stocker.

 

[XP_Slinger]

It actually runs normally if you remove the spacer and use a regular cover with a vent hole. I own a 371K power head and tried. But that saw is stock so I dont know how it performs in moded saw. It just rusn and cuts like a stocker.

Yes sir that’s the fix. Did the same thing to my 357.

 

[XP_Slinger]

I got dooped on fleabay for a “genuine Zama “ carb. Sending the piece of crap chinesium imitation back. Ordered another genuine carb from baileys but it’s on back order...so I wait.

 

[huskyboy]

A little different “animal” than a 372 (more displacement and slightly more powerful)... but still relevant to the thread as they both use variations of the zama c3m. In this video I had thinned shafts and drilled jet in the “before”... and “after” is when I bored out the venturi and got the results below.

Be interesting to see the gain on a 372.

 

[Terry Syd]

Good comparison, but it is still 'cookie cutting' (ie: high rpm power). What the carb mods do is really bring in the low end torque.

It would be instructive if you had stopped in a cut, then hit the throttle and see how the saw responded. The mods really make a difference when you are working, like doing a back cut, stop and check the hinge, and then hit the throttle to continue.

 

[huskyboy]

Good comparison, but it is still 'cookie cutting' (ie: high rpm power). What the carb mods do is really bring in the low end torque.

It would be instructive if you had stopped in a cut, then hit the throttle and see how the saw responded. The mods really make a difference when you are working, like doing a back cut, stop and check the hinge, and then hit the throttle to continue.

 

[XP_Slinger]

A little different “animal” than a 372 (more displacement and slightly more powerful)... but still relevant to the thread as they both use variations of the zama c3m. In this video I had thinned shafts and drilled jet in the “before”... and “after” is when I bored out the venturi and got the results below.

Be interesting to see the gain on a 372.

Sounded about the same to my ear Mason. Not to be that guy but you used a different cutting technique before and after the mod, that could’ve been the perceived gain right there. Tough to tell from my armchair dyno lol. A damn fine running saw either way.

 

[XP_Slinger]

Good comparison, but it is still 'cookie cutting' (ie: high rpm power). What the carb mods do is really bring in the low end torque.

It would be instructive if you had stopped in a cut, then hit the throttle and see how the saw responded. The mods really make a difference when you are working, like doing a back cut, stop and check the hinge, and then hit the throttle to continue.

Agreed.

 

[XP_Slinger]

@Terry Syd Would you be able to post a pic of the modded pliers you use to remove the main jet? My carb shipped today and with any luck I’ll be working on it this weekend. Thanks

 

[Terry Syd]

I don't have a camera I can use. All I did was take an old set of diagonal pliers and grind down the underside so that the jaws came together on a flat plane. Then I put a small 'V' or 'U' on each side of the jaws so that I got a better grip for turning the jet. The modified pliers tend to put four little marks on the jet where the 'V' on each jaw contacts the jet. A Dremel disc is all you need to make the 'V' or 'U'.

What is important is being able to grip the jet 'flush' with the body of the carb. The higher you grip the jet, the more likely you will cut the top off.

Rich used an electronic nippers that was already flat along the cutting surface.

If you cut the top off, you will have to take a small Dremel bit and grind around the jet to get it out. Then you will have to GB Weld the jet in place after modding the air bleed hole.

 

[XP_Slinger]

I don't have a camera I can use. All I did was take an old set of diagonal pliers and grind down the underside so that the jaws came together on a flat plane. Then I put a small 'V' or 'U' on each side of the jaws so that I got a better grip for turning the jet. The modified pliers tend to put four little marks on the jet where the 'V' on each jaw contacts the jet. A Dremel disc is all you need to make the 'V' or 'U'.

What is important is being able to grip the jet 'flush' with the body of the carb. The higher you grip the jet, the more likely you will cut the top off.

Rich used an electronic nippers that was already flat along the cutting surface.

If you cut the top off, you will have to take a small Dremel bit and grind around the jet to get it out. Then you will have to GB Weld the jet in place after modding the air bleed hole.

Pretty much what I was thinking needed to be done. Thanks for the details

 

[49er]

I don't have a camera I can use. All I did was take an old set of diagonal pliers and grind down the underside so that the jaws came together on a flat plane. Then I put a small 'V' or 'U' on each side of the jaws so that I got a better grip for turning the jet. The modified pliers tend to put four little marks on the jet where the 'V' on each jaw contacts the jet. A Dremel disc is all you need to make the 'V' or 'U'.

What is important is being able to grip the jet 'flush' with the body of the carb. The higher you grip the jet, the more likely you will cut the top off.

Rich used an electronic nippers that was already flat along the cutting surface.

If you cut the top off, you will have to take a small Dremel bit and grind around the jet to get it out. Then you will have to GB Weld the jet in place after modding the air bleed hole.

I messed up the jet when I tried to remove it and then because I had nothing to lose took it to the drill press and by luck it came out in one piece. I had another jet. The next carb I wanted modified I sent it to Poleman.

 

[Terry Syd]

Yeah, the work Rich did was the best deal around if you were going to rebuild your carb. You told him about your saw and he took a brand new inexpensive Chinese carb and modded it for your saw.

You didn't need to mail him anything, purchase any tools, a rebuild kit and then figure out how to do the work. Plus, he had the experience to drill the carb correctly for your saw. I'll bet there are guys out there that if they are selling their saws are removing and keeping the Poleman carbs for their next saw.

Too bad the supply of those Chinese carbs dried up. Now you have to search for one of the old Zamas in a bucket someplace. I found one at a dealer for only $20. He had no idea what he had.

 

[I Know Something]

And I'm looking at it asking my self. Self....how's this gonna fit? Air filter too?

 

[huskyboy]

And I'm looking at it asking my self. Self....how's this gonna fit? Air filter too?View attachment 276399

It’s tight but it can fit. It all kind of smushes together. Lol

 

[huskihl]

And I'm looking at it asking my self. Self....how's this gonna fit? Air filter too?View attachment 276399

390 boot is about 1/8 inch shorter, if that helps at all

 

[Ronie]

I second it will fit, on the one I did I had to trim the plastic on the throttle cable so it would close all the way.