i bought a K&N powerlid along with a pro circuit T-4 pipe and the jets that came with the powerlid were 155/175. that seems like a really big difference since the stock were 140/145. can anybody help me out here?

 

Put em in see how it runs.. change the jets see how it runs jetting is a trial and error thing.. no one can tell ya what to do all bikes are differnt all elevations are differnt, temp makes a differnce.. humidity makes a differnce Trial and error jets are cheep just work at it.

 

That is a large difference, I wouldn't do it. I originally had a 145/150 and the dealership had a 165. I thought about running the150 with the 165 and a few folks including Yamaha told me not to do it so I ordered the 160. I just installed 160/165 on mine this week with a White Bros e-series full system and the Pro Design K&N. Haven't taken it out yet but sure ran good in the yard. I also adjusted my valves while I had the front plastic and the gas tank off. I've read some bad things about the DJ and other after market jets, so I would stay with the Mikuni.

 

I have the K&N slip in filter and the K&N powerlid, along with the GYT-R pipe, I live in the Texas panhandle (elevation approx3500ft) I have the 160/165 jets in my carbs and it seems to run great. I would stick with the mikuni jets, i got mine in the GT-R jet kit, it had every thing i needed including the new pilot jet (25) AND the new needles. Hope his helps.

 

I just put a DMC Alien full system on my 04 Raptor 660 with a K&N filter and I used 160/165 on the mains and 25's on the Pilot. I have tested it out a little and it seems to be close. I have good low end but have not tested the high end really just yet. The low end is good enough to go from a rolling idle to a wheelie with just the flick of the throttle. I need to also add that I in the middle on the needle and 3 turns on the Mixture screw. I also have the snorkel off at this point. I hope to go play in the sand next weekend to do some fine tuning.