I recentlly bought a used 2005 YFZ450SE and at high RPM's in forth and fifth gear it stalls out and I don't know why. It only stalls for a second and then begins to accelerate again. What could be the problem? I don't know if it has been jetted, I think it has because it runs stronger than other stock YFZ's I have ridden in the past. It also has a pipe and K&N. Any help is appreciated.

 

Sounds like you might be lean. I think it pops when its rich and stalls out and gets hot when its lean. What do your plugs look like?

 

Sparky is right on that one, you may need to change your main jet up one or two size's.

 

You might be hitting the rev limiter if you are at to high of a RPM. It kinda cuts out for second when you hit it.

 

I think it is the rev limiter, mine does that too but mine is also jetted wrong and getting to much gas, so it is running pretty horrible anyways.

 

If it is the rev limiter what do I need to do to fix it, if anything

 

The plug is also black, any help?

 

If its the rev limiter i would adjust your throttle screw in a bit (if it has one) so you never hit it. Not good for the bike anyways and no bike makes the most power on the rev limiter.

 

That is probably it because the throttle limiter screw is missing I'll try to find a replacement for it. What does it mean when the plug is black?

 

that it is getting too much gas