Topic: KibbleWhite valve spring shims, Use them or not?

[Blue2swing]

Hey guys, I have a 1975 stock cb750. I have no real mechanical experience but thought it to be a fun challenge to attempt a full engine rebuild myself with the knowledge obtained from this wonderful site and several shop Manuals. I'm at the point in my rebuild where I'm finishing up the top end. I installed new Kimbblewhite valve springs but decided to not use the valve spring shims that came with the kit. The truth is I really have no idea what they are for or how to know when or when not to use them. I figured the stock set up had no shims on it so I would leave it that way. When finished the bike will be used for city driving and a few leisure country rides. No racing what so ever. My question is, will I regret not looking further into the use of these shims? Or am I ok leaving them out? I'd hate to finish up the build to find out I have to pull the engine again to fix something I can take care of right now. Thanks for any Advice you can provide!

Much appreciated- Isaias M.

[Don R]

 I haven't used the kibblewhite springs but are the shims used to protect the aluminum spring pocket from wear?  My thought is always, if they didn't think we needed them, they would save the money and not include them in the set.

[Blue2swing]

Thanks for the reply Don. I used the original Honda Valve Spring seats with the new Kimbblewhite springs (Honda part 14775-300-000) so the springs don't sit directly on the aluminum. Should I remove the original Honda spring seats and use the shims only? Or do I combine the two? I'm very much a beginner at this. Im 5 months into this engine rebuild and am constantly learning new things. Thanks again.

[PeWe]

The shims are used for correct spring pressure/height. If too sloppy the valve might float too easy.
All heads are probably not exactly the same in the height between seat area for the valve vs seat for the spring. If seat has been cut, the valve will be displaced upwards. Spring force will be less.

This thread has information about it.
http://forums.sohc4.net/index.php?topic=44023.0

[Blue2swing]

Thanks PeWe. That was exactly what I was looking for. The Kimbblewhite kit is specifically for the CB750, so like Don said, if they didn't want you using it they wouldn't have included it. I guess I'll be unbolting the head from the block and taking some more measurements to insure an install height of 1.34 as the packaging suggests.

[PeWe]

You can check with MRieck too jsut for sure. He has seen some CB750 heads.

[flybox1]

Thanks PeWe. That was exactly what I was looking for. The Kimbblewhite kit is specifically for the CB750, so like Don said, if they didn't want you using it they wouldn't have included it. I guess I'll be unbolting the head from the block and taking some more measurements to insure an install height of 1.34 as the packaging suggests.

Usable limit range is also listed in Hondaman's book.

[madmtnmotors]

I installed new Kimbblewhite valve springs but decided to not use the valve spring shims that came with the kit. The truth is I really have no idea what they are for or how to know when or when not to use them. I figured the stock set up had no shims on it so I would leave it that way. When finished the bike will be used for city driving and a few leisure country rides. No racing what so ever. My question is, will I regret not looking further into the use of these shims? Or am I ok leaving them out?

     Under normal use, I would not worry about it. You should be fine.

[Blue2swing]

I sent MRieck a PM this morning. He also said it would be fine without the shims. A relief to me as it would be the 2nd time I'd have to reassemble the head as someone forgot to install the valve stem seals the first time around . Thanks for all the help everyone, I truely appreciate it!

-Isaias

[Bailgang]

I installed a set of kibble white valve springs in my son's 750 and I was actually apprehensive of using the shims because they were substantially stiffer without them as it was compared to stock springs, my concern was that I didn't want the valvetrain beating itself up any more than needed due to the increased spring pressure and the cam that was being used was a stock F2 cam. I put the shims in anyhow and the valvetrain didn't seem to mind it.

My guess is that unless you're using some high lift performance cam then you would be fine without them on a stock profile cam.

[PeWe]

Stock cam is another thing. Hot cam will have higher lift and more abrupt closing with the rider that find max hp at 9000 rpm :-)