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450r to x conversion

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i just finished working my buddys 03 crf450r and his valves we beyond the service limit and he has to have the seats redone but he wanted my to convert the top end into the 450x setup? he told me u have to put in a 450x piston and valves. but stainless steel valves for both r the same right? so is the piston also right? can someone clarify this decision cause its not making any sense to me.

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Why would you want the detuned X setup?

But a 06-08 head complete and run it. APE makes a great ready to run head with SS valves. you can go to the newer 07-08 style for a bit better flow and velocity.

www.bigborethumpers.com

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The x model has a different cam, but I don't know about the valves (I think they are the same). Why would he want to convert to a cam that pretty much every one that owns one switches out for either the r cam or an aftermarket one? The other difference is the transmission gearing ratios between the two. Another thought for your friend is just to fix and sell the R and buy the X. It takes more money to convert the R to an X than to just buy an x (I know this from experience).

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The x model has a different cam, but I don't know about the valves (I think they are the same). Why would he want to convert to a cam that pretty much every one that owns one switches out for either the r cam or an aftermarket one? The other difference is the transmission gearing ratios between the two. Another thought for your friend is just to fix and sell the R and buy the X. It takes more money to convert the R to an X than to just buy an x (I know this from experience).

:bonk:

Best answer here.

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personally i dont cause its not my bike but my friend wants to swap the piston and valves to an x version because hes under the impression that they are more durable and he wont have to replace the piston or do a valve adjustment as much. he doesnt want to switch the cam.

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The X valves arent any more durable than the standard stainless valves that you get from Kibblewhite or ProX.

The main issue with the OEM's is they call out the same springs for the stainless valves which is fine for the X engine since it doesnt rev like the R does. You can end up with some significant valve float running the heavier Stainless valves with the same springs.

Its a better swap to the ProX or KW valves with the springs.

An even better, easier setup is the Bigbore thumpers head with stainless in it from the get go.

Which ever, you need to get the seats cut if you rebuild the head you have.

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ya the seats r getting redone first and ya the springs and valves i can get in a kit from KW for 170. i was just curious if the valves would fit and work. my biggest concern is the size of the x piston compared to the r piston since the first 450x wasn't made til 05 and his 450r is an 03.

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