it seems that my 400 is slower at building rpms then others the moter is in good shape with 126lbs of comp do you think it could be my reeds i have never really looked at them so im thinking that may be the case if i get some new ones can i just buy new (pettels?) or do i have to buy a hole new cage i cant afford v-force of boysen right now...

 

Pull your reeds out and look at them look for chips in the petals and then hold them up to the light and see if you can see light coming through where they seat on the cage. You can just get replacement petals!

 

If you have the stock reed's ,i doubt that is the problem.The stockers very seldom get that wore out.It is worth looking at though.

 

clean the air filter check the plug clean the carb that may be the problem and check the vent lines from the card and fuel filter

 

there a lot of thing that make building rpm faster,,,it can be worn helix,it can be primary spring wear out,i'm sure it is the belt tough,,
it can be cauze it is too lean.

 

Too fat on the jetting can do that , also 126 is a little on the low side, I would say it needs to be closer to 145-150. The secondary clutch buttons worn down or a worn out belt could also be causes.