Valve spring replacement??


New Member
I'm putting my 75 cb360 project back together with new rings and am finding the free length of my inner valve springs severely short of the 1.5709" service limit. I'm at 1.510" consistently. My outer springs free length are around .010 to .020" short of the service limit 1.8819".

Do I need to replace them if this isn't gonna be a hot rod? What am I to expect for performance loss?


Split personality, I fake being smart
You won't really get any performance drop off until it's at high rpm when valves may 'float'.
As the 360 needs to be over 6,000rpm to work OK you are limiting rpm range but should still be safe to around 9,000rpm.
You are measuring with a caliper or micrometer?
You may be cranking down too hard or measured 'off the flat?
Springs should be pretty loosely held and free to move in contact surfaces
I just measured a few springs and got between 1.895" to 1.905" for outer's with 1.520" to 1.525" for inner's
There is also a possibility the service limit is incorrect, Honda often changed inner springs length and spring rate without even sending dealer service bulletins


New Member
Ok, I'll put it back together with what I have. Not going to be a hot rod. I measured at the longest part of the spring, not flats. For fun I think I'll test them for force using a press and scale.

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