power valve size

[elliottles1]

folks,

i have fitted a new old stock tzr125 barrel to a project of mine, so, standard size bore. however the power valve came from a barrel that was bored to max 2mm over and had been machined back for clearance from the piston.

the bike struggles to get to where the power valve begins to open and then rips your arms off. i am wondering if this hole in the power could be due to excessive power valve clearance (as in the valve is effectively "open").

any thoughts anybody?

les.

[m in sc]

very possible the leakage is causing that. what's controlling the power valve? is it programmable? have you tired a test ride with it closed all the way and held?

[elliottles1]

M in sc,

very quick reply!

it is controlled by the standard yamaha set up (servo etc.) however i have the modified programmable power control box, which i would highly recommend. however it does not matter where i programme the valve to open, it makes no difference to the power before it opens.

les.

[m in sc]

yeah, id suspect the valve then, or general over porting or tuning. but the valve is a good place to start & go from there.

[elliottles1]

there is no tuning done. i will order and try a new valve, wont hurt to have a standard size one anyway.

cheers
les.