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I looked at Ferrea, Kibblewhite and RD Spring and don't see any valve or spring kits for the 400.

I presume that with stock cams and rev limit the stock valves and springs work fine. With track bikes that will see sustained high RPM what kind of life span do the springs have (for either tension or breakage)? Is it common to replace them every 1/2/3 years on a schedule, or just check to see if they've sacked and replace as needed? Are there any issues with valve failures?

OEM valve springs are probably much better than they were in the prehistoric times when I raced. It just seems odd to see people building engines without putting in "race" valves and springs. But so far I've not seen anyone offering those parts, so I'm presuming that is because there is no demand.

cheers,
Michael
 

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I looked at Ferrea, Kibblewhite and RD Spring and don't see any valve or spring kits for the 400.

I presume that with stock cams and rev limit the stock valves and springs work fine. With track bikes that will see sustained high RPM what kind of life span do the springs have (for either tension or breakage)? Is it common to replace them every 1/2/3 years on a schedule, or just check to see if they've sacked and replace as needed? Are there any issues with valve failures?

OEM valve springs are probably much better than they were in the prehistoric times when I raced. It just seems odd to see people building engines without putting in "race" valves and springs. But so far I've not seen anyone offering those parts, so I'm presuming that is because there is no demand.

cheers,
Michael
I can't speak to the 400, but in SV650s we ran the stock valve springs forever. Even with (somewhat mild) aftermarket cams. This was in bikes that got both sprint and endurance race usage. Never had a problem.
In general, valve springs don't seem to be a thing anymore. I raced from 1998 (starting at Oak Hill :) ) through 2010, and valve springs were just never a topic of conversation for any modern bike.
 

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2018 Kawasaki Ninja 400
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Valve springs on a stock engine will last for a long time. If you're racing, you're going to be rebuilding the engine anyway every 2-3 years depending on how hard your pushing it. If it's just a track day bike, don't worry about it unless something goes wrong, just keep up on all maintenance in your maintenance checklist.
 

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I think engineers learning how to design cams that don’t kill springs or valves, along with 50 years of experience has a lot to do with it. :)
Sure, that’s part of it. Like most improvements in mechanical things it’s the sum of little steps. Better alloys, CAD tools that allow you to accurately map valve accelerations and internal spring stress, rev limiters, etc.
Next thing you know there’s whole generation of racers who don’t realize that valve springs can fail. :)
 
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