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FCR MX 41 on my stock DRZ SM?

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dito.  everyone says the 41 is better suited for a 470 stroker.  If you get a good deal id pick it up and see if you can swap for a 39 with someone looking to upgrade...

I'm not so sure about the everyone comment even though I've heard it often enough.

 

On a "S" it would have a tendancy to bog at less than half throtle if your doing dirt riding but with an "SM" at higher speeds it might just work with something less than a stroker.

 

MY "SM" came with a 39mm from the factory when it only had 400cc so  at 434cc.. a 41mm might work but without the better "E" cams and "E" CDI  to go with the 41 at higher revs you'd be wasting your time.

 

KTMs from 250 to 500cc all use the 39. Does that mean the 39 works best in all those models?.. probobly not. But it works great for their inventory.

 

Tony

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I found a to good to pass deal on a FCR MX 41, can I jet it for my stock DRZ SM or should I wait until I get a big bore kit? Thinking about a 434 bolt on. Thanks for any input!

 

Too big for stock displacement....

You can use it on big bore , but the 39 fcr will deliver better hp and torque up to around 8,300 rpm.......

If your living above this rpm ,yes indeed the 41 will be better..

 

here is a chart...red line is a 41fcr and blue is 39fcr, mods are big bore and hotcams,yosh RS3

 

 

 

img2308a1kg3.jpg

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