I am asking this question for a friend of mine that just bought a YFZ 450 as well as a Trinity full exhaust. I know he'll need to go up on jetting and I'm assuming he'll need to bump it up at least 2 main sizes but he doesn't think so....I ride a banshee so I'm not too familiar with four strokes and their jetting needs. Can anyone tell me about where he should start with his jetting (with the exhaust) on his 450? Any help is greatly appreciated!!!

 

Try 180 main Jet and tell him to get a K&N air filter with it

 

He's working on getting the K&N filter, I think it's a must....Do you know what the stock jets are in the 450? Thanks a LOT for the help!

 

Anyone else have any suggestions? Everyone agree that a 180 main jet is the place to start? Thanks

 

Stock jetting is as follows.... pilot-42, main 158, stock needle is at 4th clip. YFZ's come lean from the factory. Make sure you use Keihin jets, remove airbox lid and I recommend getting the NCVQ needle. Try 45 pilot, 172 main and ncvq needle at 4th clip. If it pops on decel your too lean. If it cuts out or backfires on acceleration your too rich. You will also want to get a zip-ty. for your fuel screw. That will need to be adjusted for smooth idling. YFZ Central has alot of great information for this bike and jetting specs for different pipes at different altitudes and temps.

 

Thanks ALOT Deimos, that's what I was hoping to find out!!!

 

Bump to 175MJ, 45P, needle - It matters what your elevation is and if you have stock,nvcq or any aftermarket needle.