Jetting Helper

This is something I learned years ago and I still use it.

This is a little "Helper" for jetting carbs. It is a simple scale, that will help you determine what circuit, your carbs are on, when your problems arise.

We know carbs have sereval circuits and some overlap each other. It's hard to ask for help or fix it, if you don't know when the problem occurs, or the throttle position.

This is a simple tool that you can make in about two minutes. It will help you to know what circuit, your carbs are on.

All you need:
1" piece of masking tape.
3" piece of masking tape.
A Sharpie or Pen.

I am posting some pics, because I'm not a good writer.

The first is what the whole thing should look like, when finished. Then I will try to go step by step.

First Step!

I did this on top of my tool box, sorry if it's a mess.

Step 3

Step 4

Now you have an "Idle Mark" and "Wide Open".

Then I just Eyeball, the 1/2 throttle position.

Then I add the 1/4 throttle position.

Then the 3/4 throttle position.



Now when you are riding along, just look down at the throttle position.

Example: If you are at 3/4 throttle {That would be the carb needle, range} Just at the start of the main jet.

Next time you say something like - I was riding at 1/4 throttle when it started running bad. You can look up what circuit, that is.

I hope this may help others.

Simple...and smart.

I like it.

Nice and simple, I like it! Now just ebay it for $9.99 and a roll of .99 masking tape can make you a couple hundred bucks!

Looks like the one I use with my o2 sensor.

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The thing is, all of the interesting stuff happens from idle to 1/4. After that, AFR only has mild changes based on the needle shape. You really need 1/16 throttle resolution to get much accuracy.

On the KZ550 TK carbs (manual slide), the needle clip greatly affects the 1/16 to 1/4 range. After that, the main jet starts to take over, or at least has as much influence as the nedle clip. That's with a single taper needle. With a double taper needle, the clip may affect up to 3/8.

Based on different jetting combos and using the wideband o2 sensor, I've been constructing this diagram. It's not done yet, but it's close.