24mm bored 3-circuit carb for the gx390 & 420/440/460 clones

[Shepard]

Got my new carburetor today. It's a beauty with its permanent air/fuel needle broken off and glued so it can't be adjusted. It's done at the factory to comply with some screwed up rule. I'm going to try to dremel out the epoxy around the screw so I can remove it and install an adjustable needle.

[Shepard]

Very nice little carb with a lot of potential if your a machinist. The fuel air screw is fixed into the carb body with some extreme epoxy. It doesn't have a spring on it and the thread is a different pitch then the standard VC replacement carb.
I milled off all the material around the screw and exposed the end. I used a heat gun and warmed it -- finally it came out. Now the hunt is on for a replacement fuel air screw.

[raydhd]

No pics Shep ?

[Shepard]

On the left is the needle I dug out of the new carburetor. It has a much courser thread pitch. It's a break off screw just like on the right. I took the pictures with my camera phone so the close-ups aren't that good. Hope you can see the difference in the thread pitch.

[raydhd]

My carb came today. Being the Mr. Easy that I am decided to leave the idle jet alone and just add the $10 ebay adjustable main jet . I also removed the choke plate and tapped the the hole where it entered.I set the main jet at 1.5 turns as my other carb is set up. And WOW ! The thing runs great just like that. Looking down both carbs the venturi difference is obvious. A lot of tourist on the island today but between my idle at 1050 and 5000 rpms every thing worked great with just the main jet swap and choke plate removal. Another Great part from Vegascarts.

[Shepard]

I've got some good news -- I found the thread pitch on this little barb's air/fuel screw to be 4mm x .7 which is a standard thread. It's a course thread -- I used a standard air/fuel screw with ultra fine thread and over cut it with a die. It turned out perfect, I'll post some pictures tomorrow. Just wanted to share the great news, Ray's already had good luck with his -- I'm setting mine up they weekend.

[raydhd]

Have you looked at the mid range jet yet. I have to admit that I changed out the main to the adjustable, took out the choke and swapped it into the cart. I really didn't take much notice of anything else since it worked out so well.

[raydhd]

I see Russell Thompson list this carb on his site also. I wonder if he going to modify them for performance.

[Shepard]

Well I finally got my 24 setup and running. I reworked the air/fuel screw and installed one that is adjustable. On the 24 it is fixed and buried in epoxy. It runs better then before with the 21 on it. I installed an adjustable main jet kit and so far it's only been run it the shop. I'm going to road test it in the morning. The part I like best is the restart is instant. I bought 2 new toys for my ride. I have to install the tach first so I can install the Miniature NOS kit. It's a kit from Sigma 6 that is all manual control [no electronics] and uses the large 16 gram Whippits cartridges. I'll post a video of it as soon as I can.


https://www.ebay.com/itm/Motorcycle-....c100033.m2042

[sho305]

Shepard, jeez, nothing like keeping secrets! "Got the big carb on and running good except for some jetting, have to get my tach on there, blah, blah, and oh yeah I almost forgot I still have to put the NOS kit on.