LarryCo & Taffy Jetting Input

I installed the jets and needle per Larry's signature.

2001 WR426

BK Mod 0.5 sec. squirt

Gray Wire removed


152 main fuel

65 PAJ (Adjustable, screw & spring)

160 MAJ


Fuel is Super Unleaded, 89 Octane MTBE with 10% Ethanol (Winter Fuel in Colorado)

1.5 Turns out on Fuel screw

At this setting, the bike fires right up. Idle is a little uneven. Popping on deceleration.

2.0 Turns out on Fuel screw

With this setting, it fires right up as well, and idles a little better. Still slight popping on decel and idle is still a little uneven.

I pulled the plug and for the first time, it is not wet. The tip is starting to get a white/brown color. I didn't have enough time to ride much and I just wanted a little input before the weekend.

Overall, I'd say the power and responsiveness is considerably better than it was before the changes.



LOL! Wow, never thought I'd see my name next to Taffy's on a post! :)

Glad to hear your initial feedback is positive. Just out of curiousity, what jetting were you running before making the changes? Stock 2001 WR jetting?

Admittedly, I've never done much testing in the winter (colder air temps, CO gas), so I'd imagine that you can probably do better than what you have now...but atleast you're pretty darn close! Wait until the spring/summer and let me know what you think about your jetting then...hopefully, you'll find it to be even better.

Well, keep providing any feedback you can...always looking to improve!

And a special thanks again to Taffy for making it all happen...


Hi Larry,

I know that Taffy started a lot of this and helped you a lot through all your jetting experiments. I read a lot of posts with all your trial and error testing and that's why I directed the post to both of you.

I was running the jetting as it came from the local Yamaha shop.

Basically all they did was change the Main Fuel to a 160. The fuel mixture screw was @ 3 5/8 turns out. Other than that, stock needle on 4th clip, 200 MAJ, 75 PAJ and 42 Pilot.

It ran very good at low altitude, like Moab, Pawnee National Grasslands, etc. The problem was places like Red Cone (12,800 feet) and winter riding in the mountains. I've always fouled plugs but nothing like what was happening recently.

Thanks for all the help and any changes I try, I'll let you know the results.

Are you running a stock exhaust with the baffle removed? I am still thinking of using the Vortip eventually, I don't have one yet, just to quiet things down a little.



I'm running the stock exhaust uncorked (insert removed). It's been slightly modified though, due to a about 100 crashes... :)

I CAN tell you that when riding above 10K, change your jet needle to an EKQ #2.5 or EJQ #2 and go down on the main about 5. Anything under 10K ft, what you have now should work very well...

Glad there's another satisfied Taffy jetting customer! :D


I've basically mirrored everything you've done then. I just need to ride the bike more and see how things feel. I may play a little with the PAJ and see if that makes any difference. I may also try clip #4 on the needle as well.

We'll have to hook up and ride once the weather clears the snow out.



don't lift the needle-drop it. you're running rich. leaner is crisper, richer is deadening.


I just wanted you guys to know that I took the bike out again this weekend and rode it for about 25 minutes. After it completely warmed up, the popping on decel went away and the ambient air temp was about 55 F in Fort Collins at the time. I didn't mess with any settings from my last post.

I'm pretty happy with the way it runs. Much more responsive and it seems to rev quicker as well. No more popping and it does not have any bog off the bottom.

Thanks guys and I'll update my findings if I change anything later.


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