I had a mechanic friend install my slip-on pro circuit t-4, pro flow uni and adjust the jets on my 05' 660 raptor. I couldn't be happier with the bottom end power this new set up has given me. My problem is it seems to crap out at the top end of all the gears with the exception of 1st. Which means I am not being able to rap out the rpm's quite far enough before I shift into the next gear and consequently the next gears rpm's take a spit second to catch up with the throttle. The guy I had do the install said the jets didn't need replacing, but could be moved up and down in order to achieve the rejeting result. The guy down at the local atv shop wanted to sell me jets.........could this be my problem........that I didn't replace the jets or was it correct that the existing ones are able to adjust? Should I go to local shop and replace jets or could it be something else? Was my mechanic right in saying the existing jets can just be adjusted? Need info before I decide who looks at 660 next........

 

You need to rejet.The jets cannot be adjusted,the needles can be adjusted up or down but not the jets. I would get a jet kit a few extra spark plugs and have it.good luck

 

I thought the needles in the carbs were the jets? I must know less than I thought[img]i/expressions/face-icon-small-blush.gif[/img]

 

Sounds like you main jets are too small. What size mains are you running? If they are stock, get 150 and 155 mikuni main jets with the airbox lid on. Put the needle in the center position. Get #25 pilot jets.

This is where I would start if I were you.

 

I had a similar problem and changed my main from a 175 to a 182..problem solved

 

try a 146 and a 148 but buy a jet kit,then youll be pushin some power

 

I will gave you the exact answer here in a day or so. I emailed pro-circuit for you, with your post and asked for the jetting specs. I didn't know your exact location, so i said sea level, just as a starting point. Hope i can help you. Peace.