What do you think about reducing Port diameters?

[Christian_K]

I just found this via google...
http://mototuneusa.com/homework.htm
http://mototuneusa.com/think_fast.htm

Is that total BS or what do you think about it?

Thanks and best Regards, Christian

[SWR]

A lot of people say it's not done correctly and that it can be done in a better fashion, which is true.. but yes, a lot of ports these days are too big. So Epoxy has become yet another tool for more power.

[roadrunner]

I just found this via google...
http://mototuneusa.com/homework.htm
http://mototuneusa.com/think_fast.htm

Is that total BS or what do you think about it?

Thanks and best Regards, Christian

Great link Christian!

[Christian_K]

Thanks, but isn't what he describes the total opposite of what is generally taught?
And might it even be the case only for very high RPMs, as he describes it primarily for Bike engines that rev past 10.000RPM?

-Christian-

[roadrunner]

Thanks, but isn't what he describes the total opposite of what is generally taught?
And might it even be the case only for very high RPMs, as he describes it primarily for Bike engines that rev past 10.000RPM?

-Christian-

I would think that it depends on the individual engine, from what I understand intake velocity is very important for good cylinder filling!

[loudandproud]

I know numerous R1 owners that have had this professionally done and the results were noticable. On the dyno it wasnt dramatic but they noticed alot more midrange.

I never rode one before and after so I cant vouch for it.

[crazyman]

An old briggs and stratton and a new briggs and stratton 5hp both have like an inch port, where a 5hp honda has a 1/2" port. I'm of the school of thought that velocity is key, which is why IMO 305 heads on a mildly cammed 350 run so well.

The honda revs quicker than a briggs too. All stock push mower engines. The faster an engine free revs, the faster it will accelerate under load, IMHO....

[jed]

If I rember right There is no mention of horse power.
The comentary is on how much better the bike felt and pulled comming out of turns and it was easier to ride due to throtle response ECT.
IF the ports were to big to begin with, making them smaller and increasing the velocity would produce exactially what he says.
Erland can probably speed to this, he does a lot of cycle heads.

[SWR]

If I rember right There is no mention of horse power.
The comentary is on how much better the bike felt and pulled comming out of turns and it was easier to ride due to throtle response ECT.
IF the ports were to big to begin with, making them smaller and increasing the velocity would produce exactially what he says.
Erland can probably speed to this, he does a lot of cycle heads.

There's a dyno sheet... and they do gain hp.

[sc2dave]

a different idea here,but,has anyone done this to their m/c carbs or knew someone who did? I can't find anyone who has!! http://www.thumperfaq.com/downloads/JamesNOW!.pdf .more free horsepower!!