yz250 tuning
- Thread starter 74highboy
- Start date
Rot Box
Diesel and Dust
- Location
- Smithfield Utah
I pride myself in tuning 2T carbs and I'd be happy to help, but there's a bit of a drive between us :-\ What year is your YZ out of curiosity?
Rot Box
Diesel and Dust
- Location
- Smithfield Utah
94 should be a runner. That was a good year for YZ's in the day 
I like to keep the mix between 32:1 and 40:1 depending on what oil. I run Klotz super-techniplate but any good/high quality oil should be ran with modern power valves.
Standard jetting should be:
Pilot: 40-45
Main: 350
Needles are usually in the third clip (from the top) and fuel screw should be between 1 and 2.5 turns out meaning less or more is out of its operating range.
Does it smoke a lot on top or bottom? How are cold starts? This is a great way to make sure you have the pilot circuit nailed: http://www.thumpertalk.com/topic/823120-selecting-the-correct-pilot-jet-and-setting-the-fuel-screw/
Remember a bad crank seal on the wet side can cause the motor to run very rich along with a weird idle. Hope this helps,
Andrew
I like to keep the mix between 32:1 and 40:1 depending on what oil. I run Klotz super-techniplate but any good/high quality oil should be ran with modern power valves.
Standard jetting should be:
Pilot: 40-45
Main: 350
Needles are usually in the third clip (from the top) and fuel screw should be between 1 and 2.5 turns out meaning less or more is out of its operating range.
Does it smoke a lot on top or bottom? How are cold starts? This is a great way to make sure you have the pilot circuit nailed: http://www.thumpertalk.com/topic/823120-selecting-the-correct-pilot-jet-and-setting-the-fuel-screw/
Remember a bad crank seal on the wet side can cause the motor to run very rich along with a weird idle. Hope this helps,
Andrew
Last edited:
32:1 seems really rich to me. I run 40:1, but only because I don't trust the 50:1 or even 100:1 that synthetics claim can be done. I run a 2000 yz250. My buddy rides an 05 yz250, and ran 32:1, he smokes a lot, and was constantly fouling plugs. I have not fouled a plug in 5+ years.