Part# 23 on yamaha carb diagram

5 replies to this topic
  • Mrmonk7663

Posted June 10, 2010 - 12:27 PM


What kind of jet is part number 23 as referenced in this diagram"? It could also be #21 I don't know I can't tell from the diagram. When you take the bowl off in the middle is the main jet then on one side of that is your pilot and the other side is this real small jet that I am talking about. Can someone identifty parts #21 and #23 and tell me where they are looking at my carb and also what they are and the normal sizes for intake/exhaust mods.

I am looking at mine and it is a "72"



  • William1

Posted June 10, 2010 - 12:42 PM


Your first link does next to nothing for me.

The small brass jet is #21 the starter jet. It is used when the choke (really an enricher) is used. Normal sizes are a 68 and 72, most of the time.

#23 is the main jet, installed in the end of the needle jet emulsion tube. Sort of sized in 3's - 170, 172, 175, 178, 180.......

  • Mrmonk7663

Posted June 10, 2010 - 01:16 PM


ok good deal. Thats what I needed to know. Now i'm just trying to figure out if I should put a 160, 165 or 168 main jet in. The bike is popping like crazy which indicates lean correct? Right now the bike is set at

main 165
needle-jd red with clip from top
starter-stock (i have 72 but its almost 100degrees here, I dont think I need it?)

Mods-Full exhaust
Twin Air filter
Snorkel removed

Elevation -200ft

Let me know what you think before I button this carb back up. I have a 160 165 and 168 and a 170 available for the main.

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  • William1

Posted June 10, 2010 - 01:46 PM


YZ is a race bike. Do you want it to be fast or quiet? I can jet away the popping but it will slow the bike down.

Some of the popping is from your open pipe. A stocker or a WR muffler would reduce it somewhat. A WR carb too, would reduce it (it has a ACV). Make sure you do not have any exhaust leaks (used a new gasket in the head when you put the pipe on?)

You could run a smaller starter jet in the summer but to be honest, I would only swap it out if cold starts got harder to do as the temp rises and I doubt they will. My WR came with a #68 and cold starts were problematic. I put in a 72 and that cured it.

  • Mutu

Posted June 10, 2010 - 01:50 PM


Has your bike been de-restricted?

popping when on or off the throttle? what throttle position?

45 pilot? seems excessive. try #40. do you know how to tune pilot circuit?
I liked 168 on the main, you might be good with the 165.

try that needle 3rd or 4th clip from top first.

  • Mrmonk7663

Posted June 10, 2010 - 02:56 PM


I am making a jetting post. The original question has been answered and my post is deviating. Thanks.

Edited by Mrmonk7663, June 10, 2010 - 03:53 PM.


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