primary springs

[doo900]

i am wondering which primary spring is in the rx short or long ? and can you use either of them , im running a opo primary with a 52-48 Aaen roller secondary and also ecp kit ,i need more rpm on top , won't get over 10100 , really happy with set up other than a few more rpm's to get me at the 150mph dream meter

 

[black john]

spring

try the o/s/o yamaha spring that should bring the rpm up.