Want to be able to change you CAG carby jet in less than 2 minutes?

[Crash Dummy]

If you are using the original CAG carburetor and have ever needed to change the main jet you'll agree with me when I say it can be an annoying and sometimes downright frustrating experience, especially if you’re like me and your own a bike which has extremely limited access to the carby. For my bike I found I was going to have to pull the engine out just to change the jet. Thinking about the prospect of doing this brought me to come up with a solution.
The solution is to make the jet removable without needing to remove the entire fuel bowl by enlarging the drain screw large enough that the jet may pass through.

Now let’s take a look at the carburetor






This is the normal way or replacing the jet. You'll pull the fuel bowl off then you can access the jet and unscrew it.


I've taken the measurement of the jet for later reference. 4.98mm The fuel drain hole must be larger than this for the jet to pass through from the bottom.

[Crash Dummy]

As you can see it's not going to fit. It's time we did something about this.


I'm going to drill out the original hole to 6mm


I hope your wearing safety glasses

[Crash Dummy]

I haven't even got this carburetor on my bike yet and I can already feel the power.


Tapping the thread. Sorry the picture is out of focus. I was doing the tapping and my Dad was on the camera duties. I'm afraid I can't tell you which size tap you'll need. I can't even remember myself.


Confirming the fit. There is plenty of room to move the jet through the hole without touching the sides.


The thread is tapped now. Nice and clean.

[Crash Dummy]

I didn't have access to the facilities to use an O-ring for sealing here so I’ve used a piece of rubber that the screw will compress on to forming a tight seal.

As an important final step you will need to inspect inside the fuel bowl and make sure the bolt isn't protruding past the bottom of the bowl. If it is you'll need to trim it down till the screw or bolt is flush with bottom of the bowl.

Now all you need to do is flush all metal dust and shavings out and reassemble the carburetor and refit to your bike.

I hope you have enjoyed this article

Gary

[Crash Dummy]

And now we have part 2

The Jet Driver

I think this one is probably better off explained then me showing the process in which I did it but i can explain.
I couldn't get the results I wanted at first so didn't get to take any good photos of what you see in the end result.

For this one your going to need a fairly low quality screw driver with approximately a 6mm shaft to match the hole in the bottom of the fuel bowl. The reason for the low quality screw driver is you need the metal to be soft enough to work with.
A set of files and a vice
Drill and drill bits
A piece of wire around 2mm in width. I found an arc welding rod was nearly perfect.
Super Glue
Hack Saw

Now we can get started. Here is a diagram to help get you started.


The very first thing i suggest doing is getting your piece of rod and removing all the flux. If not using a welding rod you can skip the remove flux part
What you need to do is get it filed down to until it fits into the end of the jet without being too tight or flopping about either.

Next we take our low quality screw driver. The screw driver included with our CAG bikes is perfect. You need to cut the end off it then use a file to get the end of the shaft perfectly flat.
Now you need to drill a hole that is slightly larger then the rod you were filing down earlier. Your going to insert the rod into this hole and glue it in soon.

Drill the hole in the dead centre around 25mm deep.

The next step is to cut the flat head into the end of the shaft that will turn the jet.

starting out


All done

[Crash Dummy]

Not much left to do now. All that's left is to cut the rod down size so that the flat head of the jet driver makes full contact with the jet itself with the locating pin inserted into the jet itself. Common sense will tell you when it's right.

Once that is all done and your happy with how everything is looking double check that the jet driver shaft fits through the bottom of your fuel bowl. If it doesn't you'll have to file the shaft down until it fits cleanly.

The final step. All you've got to do now is put some glue on the locating pin then shove it in the hole. Give the glue a minute or two then give it a wipe over with a cloth real quick to pick up any excess. CA glue goes off and adheres when oxygen is not present if i recall correctly so the excess glue will remain wet for a short while making for a quick and easy clean up. The end result should look something like this.



Once again. I hope you enjoy this read. These things are fun to get into the shed and make and can really make your practice,race or test and tune sessions a lot easier and less stressful.

It's 6:40am now. The birds are chirping. People are getting ready to go out for their morning walk. And I'm off to bed!

Gary.

[Pocket Wog]

Well done mate,quite a little handyman arnt you Im always making shit myself to make things easier aswell,its amazing what you can do when you put your mind to it

[chatty]

Nice job well done

[Hoover]

i believe the tap you used was an M6x1.0 as thats the one i used and it turned out perfectly.

i also found just a bit larger fibre washer that fitted the new bolt perfectly.

[Crash Dummy]

Good stuff Jeremy. I would have done that right instead of using a dodgy old bit of rubber except i was limited to working with what was at my disposal.