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Cylinder head work question...

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I'm in the process of having a motor built for a 525sx (mine blew). The head is already ported and has HD springs. The mechanic suggested new valves since the piston hit em. They'll be flat which I guess increase compression from 12.0 to 12.6 to 1. Supposedly, it'll have more RPM.

So here's the question(s): Why are stock valves on a KTM bad? Something about when they break they break everything...

Any idea what the larger valves will equate to HP wise with the extra revs? I was told headwork on a comperable bike gave an extra 3000rmp, seems high anyone know this to be true or false?

Is it worth putting a cam in since everythings in a box and if yes how many extra ponies?

Thanks

Oh and if it matters it's a supermoto.

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A cam will move the power around i.e. more top less bottom it will not give you more overall power. Take the HotCam 525 cam for example you will loose 17% off idle power and gain 8% on the top. with a 7000 rpm power crossover. If you install a hi compression piston with the cam it will offset the power loss quite a bit. I wouldn't use less than a 13:1 piston with this cam. Keep in mind you will have to run either a blend or straight race fuel with any compression over 12:1.

When valves break on any MX motorcyle you can almost bet everything it comes in contact with is going to break unless your right a idle or maybe float one then you may get lucky and just bend a valve. The '03 450sx had bad valves they had a problem with one of the Ti suppliers using a cheap grade of Ti. But from what I have seen the 525 didn't share the same problem.

I didn't do the math but a .6 increase in compression from using flat valves seems aweful high.

No matter what you do to the engine you won't get any more revs out of it unless you reprogram the CDI. It has a rev limiter set at (I believe) 10200 rpm. I wouldn't try pushing the stock single cam valve train to 13000+ it can't handle it.

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Thanks for the input I didnt realize that a cam redistributes power vs giving you more. I think I'll just stick with the headwork for now since I need new valves anyway.

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