Maintenance & Technical > KX500 Steel Frame Conversion (SFC)

my 2001 KX 250/500 conversion

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cutting torch:

--- Quote from: KXer on August 03, 2010, 11:02:53 AM ---Been riding the beast at the local MX tracks, and found out last night that both my head stay AND front engine mount are broken.  How are other engine mounts holding up on the conversions?  My engine mounts were gusseted and everything, oh well.  I need to add another pipe mount anyway.

--- End quote ---

Pics of the problem areas would help us with suggestions......

torch

junk man:
I wounder if any other builds have broken front mounts ? and what kind of head stay he's using
If mine brakes i might sleeve the frame and use the stock engine plates off the 500 i was going to do this but the 250 frame is narrower and i didn't want to flatten the tubes but if it brake is on

just an idea JM

BDI:
My 2002 is fine. My front mounts are simply the sock 250 mounts cut down. I did a bunch of practice welding on a junk 250 frame until I got my mig welds to look just like the factory welds and then went for it. As for my head stay I had a couple of funny comments made about my bike when I was building it. One was when I asked my buddy charlie tredwell who builds race car chassis if he thought my head stay was going to be strong enough. He said ya it would be strong enough for a shock mount on a trophy truck. I think the importance of and the designe of the head stay has been missunderstood by quite a few people, especially on the steel frame bikes. I realized how much demand was put on the head stay when I learned that the kx500 would blow fiber head gaskets do to the head flexing in the head stay area.

KXer:
My forward enging mount had/ has a 90* gusset on it for strength.  The actual engine mounts are 3/16ish thick (think shock tabs), and the head stay was the piece together unit from Jfab, with double row tig welds.  It "seemed" to be bulletproof.

Does the head stay need to be rubber mounted?

I have yet to take it apart to see what failed on the head stay, I'm assuming the steel became brittle after welding, grinding, welding etc getting it 100% perfect.  Also have a good idea of how i will add a gusset down the center for the 3rd headstay for this monster.

BDI:
If you try two weld thick metel to thin metal you will either get the thin metal way to hot in order to wled the thick metal and this will result in embrittlement and cause the base metal to fail. Or if you run at the right heat for the thin metal you will not get good penetration on the thick metal and you will have a cold weld that will break off the thick metal. I would imagine you had a hard time with this, probably did some grinding and some hole filling during this would be my guess.

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