Simplified---Adding A High Speed Circuit To A WG Carb

[Mastermind]

Hello all. I have questions. I have old husqy 3120 and old carb without H hole like in 1st post this thread. I can modified this carb and added H jet or need like 1st post?

Yes. Same process. You just have to accurately drill the pilot hole.

 

[huskihl]

Yes. Same process. You just have to accurately drill the pilot hole.

His is different….original

 

[huskihl]

Hello all. I have questions. I have old husqy 3120 and old carb without H hole like in 1st post this thread. I can modified this carb and added H jet or need like 1st post?

It can be done but I don’t recommend it with that particular carb. Yours is the early one with the threaded main nozzle

 

[Racer]

Yes. Same process. You just have to accurately drill the pilot hole.

It can be done but I don’t recommend it with that particular carb. Yours is the early one with the threaded main nozzle

Ok thanks guys. I drew a simple scheme, indicate my mistakes please

 

[huskihl]

Ok thanks guys. I drew a simple scheme, indicate my mistakes please
View attachment 405418

Your main jet is not the normal check valve /nozzle. If you run your new H jet fuel into the existing numbered jet, you aren’t really adding fuel

 

[huskihl]

Basically, you have a precision hole in the aux jet, say 1.2mm, from the fuel bowl down to the screen at the bottom of those threads. You can’t add an additional 1.2mm worth of fuel from your new H jet mid stream of the original 1.2mm jet and expect it to flow more fuel

 

[Racer]

Basically, you have a precision hole in the aux jet, say 1.2mm, from the fuel bowl down to the screen at the bottom of those threads. You can’t add an additional 1.2mm worth of fuel from your new H jet mid stream of the original 1.2mm jet and expect it to flow more fuel

It turns out that this carburetor does not make sense to modernize? Better take new wg-8 (or?) and make modding?

 

[huskihl]

It turns out that this carburetor does not make sense to modernize? Better take new wg-8 (or?) and make modding?

It’s not that you can’t do it, but I can’t explain well enough how to do it. I have done it once successfully but you’re taking a chance on ruining an early carburetor that isn’t made anymore.

I would recommend buying a new replacement carburetor and modifying that one. It will be straightforward with the info provided in the beginning of the thread

 

[Racer]

@huskihl thank you man+

 

[Mastermind]

It’s not that you can’t do it, but I can’t explain well enough how to do it. I have done it once successfully but you’re taking a chance on ruining an early carburetor that isn’t made anymore.

I would recommend buying a new replacement carburetor and modifying that one. It will be straightforward with the info provided in the beginning of the thread

Unless it's a primer bulb carb, it has the same nozzle. I think I can see a choke shaft.

 

[huskihl]

Unless it's a primer bulb carb, it has the same nozzle. I think I can see a choke shaft.

Not certain about the choke but it has the early screw in brass nozzle

 

[Mastermind]

Not certain about the choke but it has the early screw in brass nozzle

I hadn't even noticed that. I was looking at it as if it were the jet.

 

[legdelimber]

You guys mind if I mention that the screwdriver tip needs regrinding or replacing?
That slot in the jet is pretty roughed up from it.
Just a bit more twisting and the burr could be left dangling.
Wouldn't be much fun if it found its way into the metering lever area.

 

[Traprunner]

It can be done but I don’t recommend it with that particular carb. Yours is the early one with the threaded main nozzle

So just curious out of all the available carburetors for the 3120 what's the best overall one performance wise? Wg 6,7,8,10 ect? And easiest to modify?

 

[huskihl]

So just curious out of all the available carburetors for the 3120 what's the best overall one performance wise? Wg 6,7,8,10 ect? And easiest to modify?

Performance is the same.
Most common are the wg-7 and 10

 

[CabanaSur]

This pilot hole is the right size to run a 4mm bottom tap in to create the threads...

View attachment 278784

....but first you need to drill into the main well to feed the main nozzle.

In order to keep the drill centered, you need a steel bushing that just barely slides into the hole.

View attachment 278785

I make the hole into the well .050", so my bushing has a hole that my .050" drill bit just fits thru.

View attachment 278786

Simple huh?

Hello everyone

I'm also trying my first carb mod but i have a question here.
You make a bushing to fit in the standard carburetor hole and drill a .050" (1.27mm) in to it to center the drill i get this part, now for my question. Your drawing says that the needle has a diameter of .080" (2.032mm) but how does this work? Should the needle diameter be smaller (.050" (1.27mm)) or does the hole in the bushing needs to be bigger (.080" (2.032mm) to fit into the carb? Or am i wrong somewhere.

I'm form Europe so i use the metric system so i might be reading your drawing wrong.

Thanks in advance!!

PS: Metric diagram would we awesome XD

 

[Hinerman]

@Mastermind

 

[Mastermind]

Hello everyone

I'm also trying my first carb mod but i have a question here.
You make a bushing to fit in the standard carburetor hole and drill a .050" (1.27mm) in to it to center the drill i get this part, now for my question. Your drawing says that the needle has a diameter of .080" (2.032mm) but how does this work? Should the needle diameter be smaller (.050" (1.27mm)) or does the hole in the bushing needs to be bigger (.080" (2.032mm) to fit into the carb? Or am i wrong somewhere.

I'm form Europe so i use the metric system so i might be reading your drawing wrong.

Thanks in advance!!

PS: Metric diagram would we awesome XD

The .050 hole becomes a seat for the needle....which is .080. If the needle was smaller than the seat, it would not restrict fuel flow very well.

 

[CabanaSur]

The .050 hole becomes a seat for the needle....which is .080. If the needle was smaller than the seat, it would not restrict fuel flow very well.

Ah yes of course.. I've been reading a lot about the mod these past weeks and think that in my head i'm making it much more complex than in actually is. Just don't want to ruin a brand new carb. I'll get the parts ready and post when it its done!

Thanks!