my buddies got a 03 650 vtwin and wants to know if a knn and jet kit is possible with out a pipe (dosnt want a louder bike) is it worth the money vs the amount of power you get?

 

I have to yes go for it but he should also look at the air intake snorkel too, they are restrictive. You can purchase an after market one or do the inexpensive radiator hose trick. You will need to re-jet, typically 1 size up on each carb. Note: they are different sizes front to rear. I forget which is which but I think the rear is larger, move it to the front and buy 1 new rear jet.

It makes enough of a difference (imo) to warrant the cost. There is also a muffler mod he can do that increase the power as well (not quite like aftermarket) but doesn't increase the sound level much at all.

Do a search in Kawasaki and there will be a wealth of info there or look at either NYROC or KISSSOFDEATH's sites. HTH