high velocity intake ports

[jha07]

I've been reading the site http://www.mototuneusa.com/ and they claim that smaller intake ports will increase horsepower. Just wondering if anyone on here has tried it to their DRZ.

[Wayward Son]

on some stuff.not everything.

[a109drvr]

on some stuff.not everything.

Just curious Burned, do you mean you have tried it on some stuff, or that it only works on some stuff. I would really like to know the results if anyone has done this to a single cylinder dirtbike.

I read every page of the mototune website (took a while, the graphics make me wanna 😢 ) and most of it makes sense to me. But I wonder if his method works well on something besides 15,000 rpm racebikes. I know there was a letter he posted from someone who did the 65% port height method on a Harley but it is easy to make a Hawg breathe better.

[Wayward Son]

it all depends on the cylinder head.

[Redrodent]

I measured the ports on my E model. They're very, very close to the size Mototune recommends. My TLS took about 5 packs of epoxy to shape. There was no improvement on the dyno, but it improved the torque curve alot.

[jha07]

I measured the ports on my E model. They're very, very close to the size Mototune recommends. My TLS took about 5 packs of epoxy to shape. There was no improvement on the dyno, but it improved the torque curve alot.

So you measured the E's port diameter and they are 65% of the valve diameter?

[Redrodent]

Yes, see, your old over weight iron dinosaur really is cutting edge 😢 Within 1 or 2mm, if I remember correctly. I was going to try the DRZ first, since it was a single, but after checking there was no reason too. For reference the TLS needed about 8-10mm to fill.

[Wayward Son]

just fyi ron hamp (RHC here on TT) says with a big bore cylinder a drz head is better than the honda head.

ron makes 60hp out of crf 450's with stock bore. 😢