Exhaust pipes for YZ400F?

Does anyone know what the measurements of the best pipes are? In other words, what pipes work best, tapered or stepped? Straight diameter? What's the head pipe and silencer length? Does the pipe material play any type of significant role?

Also has anyone tried any aftermarket cams? What company and was there any dyno testing involved after the cams were installed?

It depends. What works for one person may stink for another. The tapered headers increase low and mid range torque, but do nothing for the high. The oversize headers decrease the low end, but allows the bike to rev faster and harder in the upper rpms ranges. The silencers generally speaking are "all-around" pipes, unless it specifies otherwise. So a tapered header w/ stock silencer (what I run) will hit a little hard down low, will take away some of the mid-range hit (because the power is higher thus the hit or increase is less noticeable) and does absolutely nothing to the top end.

The same combo with an E-series silencer feels almost identical powerband wise, but there's a bit just more power everywhere. The power curve just moves up a notch.

Be realistic as to where you want the power.

Also remember $20 worth of needles and jets will increase power just as much as a pipe. Food for thought...

Thanks for the input mcarp!

I also found huge gains in torque and hp in the middle and bottom by using a set of vernier cam gears and a set of cams. I just got it off the dyno today after adjusting the cam lobe centers to 108 exhaust and 106.5 intake. That change from stock improved the compression by 10 psi on a cold, dry engine. I'm not even sure if that is the optimum settings for the cams either, more time will tell. It improved the throttle response and low and midrange power by quite a bit, and didn't hurt the top at all. I'd put the power numbers up but, I want to make sure they are repeatable by doing some more testing first. Then some riding to make sure the increases are where they need to be in the rpm range.

Tony www.ciaysr.com

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