07 yzf 450

I recently purchased a new 07 yzf 450 from a local dealer. I have had the bike about a month with the same problem. It has a hesitation with a blip of the throttle and it pops like crazy when you let off the throttle. I have gone through the carb and found some trash in the bowl, cleaned it all up blew out every orifice and reinstalled it. It runs great, but it annoys me the way that it does not rev cleanly and then pops off throttle. I have adjusted the pilot screw and it idles better at 3.5 turns out from seat and I think I need to go to a bigger pilot jet. Bike is completely stock. 160 main jet, 45 pilot jet and the clip is in the 4th position. Any opinions would be greatly appreciated. I have also read a little bit about the zip-ty carb mod and would like to hear some more input on that as well.

Try a 48 pilot, 165 main and a 40 leak jet...adjust fuel screw to your liking. I believe you will find the bike will respond much better with no popping or bogging.

I recently purchased a new 07 yzf 450 from a local dealer. I have had the bike about a month with the same problem. It has a hesitation with a blip of the throttle and it pops like crazy when you let off the throttle. I have gone through the carb and found some trash in the bowl, cleaned it all up blew out every orifice and reinstalled it. It runs great, but it annoys me the way that it does not rev cleanly and then pops off throttle. I have adjusted the pilot screw and it idles better at 3.5 turns out from seat and I think I need to go to a bigger pilot jet. Bike is completely stock. 160 main jet, 45 pilot jet and the clip is in the 4th position. Any opinions would be greatly appreciated. I have also read a little bit about the zip-ty carb mod and would like to hear some more input on that as well.

Yea, you are running lean it sound like. Is your fuel mixture screw 3.5 turns out? If so, you really shouldnt have it more than 2 turns out but you can get away with it. Just need a bigger size pilot:thumbsup:

Thanks guys! I thought that was what I needed to do. I guess I just wanted to hear it from someone else. The more I opened the pilot screw the more it idled up and that just didn't seem right. Do you think I need to jet the main up as well? I have main jets but not pilot or leak jets so it may be a few days before I get it changed.

I was going to say the same as croggr. 165mj/48pj try that. You can also go with a smaller leak jet for a richer ap squirt. Have you done the o-ring mod?

http://www.thumpertalk.com/forum/showthread.php?t=624773

No I have not heard about the o-ring mod, but looks fairly easy to do. What exactly does this help? The only thing I have read up on prior to this is the zip-ty mod.

No I have not heard about the o-ring mod, but looks fairly easy to do. What exactly does this help? The only thing I have read up on prior to this is the zip-ty mod.

it reduces the amount of fuel that the accelerator pump squirts into the carb, making for a crisp mixture and somewhat of a snappier throttle.

it reduces the amount of fuel that the accelerator pump squirts into the carb, making for a crisp mixture and somewhat of a snappier throttle.
No, this is incorrect. When the throttle is opened, pressure is applied to the accelerator pump rod indirectly by a spring; the throttle linkage winds the spring, and the spring unwinds against the pump rod actuator lever. This results in the pump rod compressing somewhat more slowly than the throttle is opened. The O-ring mod attempts to increase the delivery of fuel by the accelerator pump by adding to the stiffness of the spring, speeding up the pump stroke.

While the mod works, to some extent, the Merge Racing AP spring is a much more workmanlike way to accomplish exactly the same thing.

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