KTM 525ATV with 540BigBore! Best cam and piston rating choice?


Hello, riders!

Can someone recommend best choice for cam shaft, piston ratio?

For ATV KTM 525 with 540 cylinder?

There are some upgrade in head - intake flow are made wider till valves( intake valves std. 35mm)

Maybe someone can comment experience with results on own ATV upgrade?


I think the KTM web site has a few options on what combo works. I would say 13.5:1 port the cylinder head and use the stock cams.

Thanks, T-Rex for advice, we already go for 540, only is the price advanced to result:(

I'd go with the 8/06 cam and send the head to Dave Hopkins (member on this site) he's the RFS guru, have him unshroud the head and add his OS kibblewhites then your head will last forever and require very few valve adjustments compared to stock. Ask Dave what combo to run, he's an expert on RFS bikes. I'm not sure what size carb comes stock on the quads, but if it's a 39mm FCR I'd send that to dave and have him bore the carb to 41mm and have it rejetted, and have your AC pump tweaked.

That should provide a pretty big gain.

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