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OEM Rebuild??? Good idea or bad

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I recently bought a very clean 06 kx450f. Just out of curiousity i was looking on ebay and pricing out top ends and other items. OEM has a complete top end rebuild kit, gaskets and all, for around $150. Does anyone have an opinion on rebuilding these 450s with OEM parts?

Thanks

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Congrats. If there are no surprises you got a good MX bike.

After topics such as "Which pipe?", "Show us your pics!" and "which oil?", This is perhaps the most common thread topic in this forum. When you have a spare 2 hrs you could search for "06 piston" and take it all in.

The short answer, in my opinion, is forget about the OEM piston kit. It is the Achilles Heel of an otherwise remarkable engine which requires regular basic maintenance and in return faithfully pumps out gobs of very snappy torque from 3000 to 9000 rpm.

This is the long answer: The cast piston design is poor and it flexes across the crown, so the piston bends and/or binds on the pin, then the pin/rod bearing surfaces get galling on them, and eventually the pin breaks and you have a grenade. If lucky the piston crown cracks first and your engine gently shuts down. Kawi's fix is half arsed coating on the pin, and maybe some better casting quality in the piston (my guess). But why risk it. Get a decent forged piston (like they finally put in the '10 model). The 06 has the lightest rod and crank, so if you want peace of mind consider a std comp wiseco piston+pin which is 9% lighter than OEM.

I've done 141 hrs on my wiseco piston and still counting. But run time is only 1/3rd the story (no record of revs or throttle opening), so in my case prob the equiv of 70 MX race hours, but it blows zero smoke and runs very nice. When the OEM piston and pin came out at 35 hrs, it was obvious from the galling that I was riding a time bomb.

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