Maintenance & Technical > KX500 Original

Foam cuts down vibration?

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maddoggy:
the foam filled frame sounds like a reasonable idea, but stewart pointed out in a different thread that the crank not being in clock/timed or properly balanced is where the majority of k5 vibration comes from. i think i would chase the source of the vibes before i tried foam filling the frame. bigbellybob made a good point that the frames are designed to have a specific amount of flex, if you don't allow the flex/vibrations to go throughout the frame it will concentrate near the source and probably start breaking welds or the smaller tubes on the frame under the engine. no facts here just my opinion.   MADDOGGY

Rd:
You can get the closed cell structural foam from good boating supply companies. If I remember correctly it comes in 3 differant densities 1lb,2lb and 4lb, The 4lb being the strongest. I have used the 2lb on some boating projects and believe it would be very tricky to get into a frame before it kicked and started getting rigid. You would probably be better off using a closed cell marine foam, because it is not supposed to absorb water like an open cell foam. The 4lb is some pretty rigid stuff.

Good:
Interesting topic.

I too remember the CR250s being too rigid out of the box and I think it was McGrath who didn't like them and wouldn't ride them at first.

But, would this expanding foam add rigidity, or just dampen vibration?  Not talking the marine stuff, just simple expanding foam found at wally-world.  I wouldn't think it would make the steel frames as rigid as their aluminum counterparts, but the vibration issue might be worth looking into.  Great topic.

In the car stereo world, sound deadening is achieved by adding mass to door panels, etc.  It would be cool to inject some of that stuff into the frames.  The problem with that is mass generally = weight...

GDubb:

--- Quote from: Good on December 31, 2008, 07:29:20 AM ---I too remember the CR250s being too rigid out of the box and I think it was McGrath who didn't like them and wouldn't ride them at first.
--- End quote ---

I remember that too... he was having the new engines swapped into a modified '96 frame.


-G

Speedway73:
The stuff you're talking about is called Great Stuff.

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