It dies when you pin the throttle quickly. It sounds like some type of electrical safety feature, like the TORS on the Banshee. I've unplugged some wires, but it doesn't help. It runs fine, you just can't nail the gas from idle or low throttle.

It sounds like a jetting issue, but it did this the first time I started it after unloading it. It was bone stock. I have since installed a K&N and Dyno jet kit, removed the lid and baffle. I can't tell if it runs better, b/c I also have a Banshee that I ride and It makes the YFZ feel slow.

Thanks

 

It's lean, they all are from the factory. Jet it to 168 main, one up on the needle, and 45 pilot. Should be good then.

 

I installed the Dyno Jet Kit Stage 2. I haven't installed the needle yet, can't figure out how to get the carb out. I'm going to work on it again today.

Stock=no mods...Its not stock anymore, forgot to change it in my sig.

 

I put the Dyno Needle in......see my other post for info on that.

But I've been told, like I thought, that a safety feature, much like TORS, is responsible for the motor dying when nailing the throttle. What is Yamaha thinking? I'm not scared of a stuck throttle..I can hit the kill switch or the clutch.
But If I'm needing to wheelie off of a hill, etc., and it dies, then I'm doing a front flip.

What is more dangerous??????

 

Are you sure you have it jetted right. Mine did this when i first got it but after i jetted it doesn't do it anymore.

 

I'm not sure its jetted right, but I have larger pilots in it and airscrew at 1.5 turns out, what else could I try? I know two more guys with the same prob. Dealer told them it was a safety feature to keep the throttle from sticking.

 

odd, i havent had one problem with anything makin my motor shut off, currently im still bone stock, havent even jetted it or anything, baffle still in exhaust, lol. what year is ur YFZ again, mine is a 05 and i dont kno if they corrected that problem from the YFZ450-F to the 05 YFZ450-T...

 

Your jetting couldn't be so far off as to cause it to die when you nail the throttle. Gotta be something else. Some gunk plugging up passages in the carb or fuel line maybe. Mine ran fine with lid off and baffle out with stock jetting, ran better with 165 main, better yet with slip on pipe, at no time with any combination thereof would it die.