How To Add A High Speed Circuit To A Walbro WG Carb

[Mastermind]

This thread deals with the Walbro WG-8



Notice that there is a pilot hole here? That makes these a bit simpler.

 

[Mastermind]

First......tear em down.

See what we have to work with.....

 

[Mastermind]

Some of the stuff you'll need.

Springs, o-rings, brass washers, replacement main nozzles.


For tools......micro drills, and stuff.

Here's some drawings I made to help me keep up with the details.

 

[Mastermind]

Now.....you gotta drive out the main nozzle. And......sometimes that fubars it. Best to have some new ones on hand.

 

[Mastermind]

I made the sleeve that fits in the pilot hole to guide my micro drill. Where the tip of the drill comes out inside the nozzle well is very important. Too high, and the nozzle will never seal, too low and it's obstructed by the nozzle.


Then it's just a simple matter of drilling the hole.



And Glory !!!!

 

[Mastermind]

EDIT !!!!! I no long recommend this step. Only do this if you are blocking the main jet off.

Now, to keep the low side from pulling fuel from the nozzle area, I add a place for it to get it's supply from.


Notice in this picture that I've drilled three different holes. The top one over the main nozzle is to provide fuel to the HS circuit.

 

[jakethesnake]

Madness

 

[Mastermind]

There are several different ways I can set this carb up from this point.

One is for a mild saw that likely needs less fuel than what the stock jetting provided. These carbs are set up extremely rich from the factory.

For that situation, I plug the original jet before I reinstall it.

Next is for the saws I build for my customers. I leave the factory jet as it is. That means you can completely close off the HS circuit I created, and the saw will still start and run.......but it will be lean. You begin dialing it in by cracking the new HS jet open.....and fatten it up till it's just right.

Third.......I can make everything much bigger so the saw can run on Alky. That requires a bigger needle and seat.

 

[Mastermind]

Now........I like to add a recess to make sure that fuel can flow thru these new passages even when the metering diaphragm is pulled all the way down in the metering well.

It will flow this line.







Now it's time to make the needle.

 

[Mastermind]

Pretty simple stuff here.....just small.

 

[Mastermind]

Basically......that's it.

 

[Mastermind]

Questions?

 

[Stump Shot]

Questions?

Is the little channel you cut in really necessary, or is it like extra insurance and can you spare that dime?

 

[Mastermind]

Is the little channel you cut in really necessary, or is it like extra insurance and can you spare that dime?

I've done it without the channel.....and sometimes it will run lean. It depends on just how much fuel it's pulling.

 

[Stump Shot]

I've done it without the channel.....and sometimes it will run lean. It depends on just how much fuel it's pulling.

Ok, I'm just trying to picture it in my pea brain. Guess the well ran dry.

 

[maulhead]

Questions?

Yes, what's the purpose of that dime in poast #10?

 

[Mastermind]

Yes, what's the purpose of that dime in poast #10?

Scale.

 

[Mastermind]

Ok, I'm just trying to picture it in my pea brain. Guess the well ran dry.

Imagine the metering diaphragm pulled down as far as it can go....

 

[maulhead]

Scale.

I might be able to make change for it.....

 

[Stump Shot]

Is the inlet needle hole of ample size?