Hey Chuck. Thanks for the video, but...believe it or not...Yamaha has a mistake on their chart in the YZ250 manual. The power jet actually works from about 1/2 throttle to full open. Yes, the solenoid will close the circuit at higher rpm (to allow the engine to rev cleanly to higher rpm), and while open at lower rpm will allow a richer mixture for better throttle response. If you track the carbuetor's power jet circuit you'll see it enters the venturi at the point the slide would be about half open, so it "physically" limits the flow through the circuit from that point to full open.

Hello i have a 06 yz250 im in ohio at 850 above sea level,i have fmf fatty and shorty silencer and vforce3 reeds i ride woods and am more steady on throttle,should i run 175,45,3 clip down and 40 power jet? And i run 32:1

Best Kehin carb vid on the entire interwebs. Thanks TrueTech.

YZ250s are track bikes. If you keep the jetting from factory and then are lugging them they will foul plugs. If you want to putt around on trails, before you swap to an 18'' rear wheel or anything else determine what oil you are going to use, what ratio, and then rejet.

I picked up a 2002 YZ250 in pieces. All your YZ vids have been super helpful- from the engine rebuild, lacing up black wheels and now the carb. Thanks! Keep them coming!

The tps doesn't control the power jet solenoid in any way. The ecu triggers it and it is rpm based. Solenoid closes off the power jet at 8500 rpm.

I've got a 2023 YZ250, just put the FMF exhaust on it. Jetted it to 175/48 (FMF specs) Still drips at the pipe/silencer connection and out the tail pipe. I am running 927 premix 30:1, I am wondering if I need to go to 40:1. or maybe the bike is just not broken in yet, its got 5 hours on it.

If you use the Suzuki 3 taper needle necj like you mention do you change any of the other jetting?

Do you change power jet without downsizing pilot and main? I’ve downsized my pilot and main 2 sizes for my style and elevation but I wasn’t sure if changing power jet is gonna lean it out too much. I’m barely on the pipe most rides, not smoking, no spooge and plug is still black, not chocolate brown.. 2021 yz250 with 3hrs on it. Single track and trails

Forgot to mention air mixture screw was 1.5 turns out and the reason is that im fouling plugs,thank you

Bravo!! One of, if not the best video on this subject that exists

Thank you! Really appreciate you talking thrrough what you're doing, other videos jsut have some timnelapse with music which helps me Zero.

Thank you sir, very informative

What a great video!!

Great video. I bought a 2024 yz125x and had to change my main jet at the track. When I did it I had to unplug both the throttle position sensor and power jet connections so I could rotate the carb. Once I got the jet changed I completely forgot to plug the electrical connectors back in.....but the bike ran great, no over rich loading up like it had before and I rode all day.

Great video, thanks!

Excellent video, highly underrated KZfaq channel. Keep it up man. I’m working on my ‘98 CR250 at the moment and trying to figure out why it won’t idle. It appears to be running rich so I think I need to change the pilot jet. That being said, how many different sized power jets should I order? Just one size at a time?

Quality video. You know your shit!

Great informative video! What brand/source breather line do you use?

What is your go to premix and ratio? Awesome video and very helpful!