HEADS UP!!!

Site upgrade in progress... Core site functions are working, but some non-critical features/functions will be temporarily unavailable while we work to restore them over the next couple of weeks.

Please post any bugs you encounter, but before you do, check to see if it's already listed.

Thanks for your patience while we work to improve the community.

Sign in to follow this  
Followers 0
honyam83

Am I running lean? '01 yz 426

6 posts in this topic

I have had a problem with what seems like a "flat" spot in the throttle. my bike seems to lose power at a certain spot, less that or about 1/4 throttle. This only happens at higher altitudes. I live @ 5000' but ride in the hills 8,000'- 10,000'. I have tried adjusting the fuel screw to no avail. I have checked the jetting data base but have not found exactly what I'm looking for, here are my jet numbers.

main 155

pilot 42

starter 72

needle 3rd notch down

Any feed back will be very appreciated. Thank you.

Share this post


Link to post
Share on other sites

Provided you have checked all aspects of your pilot circuit, I would check the float height aswell.

You will find the measurement and instructions in your service manual.

Share this post


Link to post
Share on other sites

Has the outside temp risen since you last rode? If so its probably a bit rich. If it were me i'd lower the needle.

Share this post


Link to post
Share on other sites

If it's happening at higher elevations, but not lower, that indicates rich, not lean. Your main jet size should be close to right, but your pilot is still stock. You should probably be using something on the order of a 40 at such high altitudes.

On your next ride in the hills, try this:

http://www.thumpertalk.com/forum/showthread.php?t=327405

If a smaller pilot doesn't do it, you may need to change the needle to one with a larger diameter straight section.

Share this post


Link to post
Share on other sites

Thanks for the replies, Gray I appreciate all the knowledge you share on this forum. I will try what Eddie suggests next time I am out. When I get it tuned right I'll post it in the data base. Thank again to all.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0