valve springs

im looking for some stiffer valve springs so next year i can rev out my bike some more i would like to get 12k safely out of her if possible i know theres not alot of valve train weight and i could maybe get away with more but really just looking for some input on this.

some of you know my setup some dont ill list it.
81 xj650 bobbed
fuel injected
turbo on 10psi non intercooled (have intercooler for next year 15+psi)
i rev it to 9800rpms right now
it has about 3k on it since ive turbo it

 

Hiya!
I have been looking at doing the same to my xj650 as well. i know that my xj750 tended to float the valves at around 11,500 rpm. after finding valve springs from a buddy of mine that were a wee bit stiffer but keeping the same height and inner and outer circumferences, I found the cure to the problem of floating the valves. I do know that since we are dealing with an aluminum head with no steel inserts for the cam journals you have to make sure that you don't go too strong or it will cause excessive wear to the journal caps and get you some really qwik valve to cam clearance issues before you know it. one thing that I have learned about these bikes is that you have to keep an eye on that issue religiously.
One question I have for you is what cams are you using? also what did you use for the injection setup?

 

Stock cams right now and over winter I'm going to try the 650 turbo cams to see if it makes any gains (dyno testing) I'm running microsqurit with gsxr600 throttle bodies.

What valve springs did u get from your buddy?

 

anyone have any idea of a valve spring that will work and wont eat the head to death ??

 

What makes you think the stock springs will "eat the head?" The limit to revving the motor to 12K is not valve float; these motors will pull 12K easily before the valves float.

Yamaha set the redline where they did to save rods and bottom ends. Think about it: The highest redline in the XJ series was the 550s, at 10K. The bigger the motors got, the lower the redline. That's not because of valve train concerns, it's reciprocating weight. If anything, the 550s have smaller, lighter valve springs.

You're barking up the wrong tree(s) here.

Read the specs on the Turbo cams, compared to say, the 750 Seca. You might be surprised.

The sorry truth is you're gonna give up more to the middle gear and drive shaft than you're ever going to gain "hot-rodding" the motor. It was already a "racebike for the street" when Yamaha sold it.

If you want it to be truly fast, put it back in stock trim and get it properly set up.