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jasen 2007

05 YZ450F Jetting Help Needed!!!

4 posts in this topic

I just picked up an 05 YZ450. It has less than 10 hrs ride time and has never been raced and is bone stock.

This is the second 4 stroke race bike I have owned, the other is an 01 YZ426.

I am having trouble with the carb setup on the 450. If I whack the gas hard from idle of just off idle it falls completely on its face. It likes to stall in corners pretty easy. Im just not sure what direction to start. I have the clip in the middle position, 165 main and 55 pilot. I ride elevations 1000' or less.

Is there something on AP I should be looking at? Are my jets way off?

Also the temp is about 40* right now.

Any help would be great.

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Your pilot is certainly way off. It should never be bigger than a 48 under any circumstance, probably no larger than 45. That's why it's stalling going into corners, most likely.

Read these two threads:

http://www.thumpertalk.com/forum/showthread.php?p=2881699#post2881699

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

Then look through this one, being certain to read Post #15 first:

http://www.thumpertalk.com/forum/showthread.php?t=694916

There is no reason to expect a thumper to be able to tolerate having the throttle "whacked" right off idle. It should respond reasonably well, but you do also need to learn to "roll" the throttle quickly rather than snap it open. Accelerator pump timing, one size smaller leak jet, and the "O-ring mod" (or much better, a stiffer AP linkage spring from Merge Racing, will fix this if it's still a problem after you get the jetting right.

You may also want to consider the CDI unit from either an '04 or an '06, too.

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ok, so after changing jets several times i decided to check the squirt duration of the AC, well there was none. After completely assembling the carb and unplugging the AC jet, I'm happy to say it feels very close.

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