Rotate your head for increased performance and a cooler running engine.

I woke up this morning with a strange thought. Kawasaki and other motorcycle and snowmobile builders have really gotten their engine design wrong for years. Why do they always put the carburetors in back and the exhaust out front? Have I forgotten some important fact of physics that would blow this whole idea? It would seem that there would be several advantages to placing the carburetors on the front side of an engine. First, upon acceleration, the inertia of the air and exhaust would tend to flow through the engine. With the carbs out back, we have to grab the air and force it to move in the opposite direction the motorcycle is traveling. Another benefit of having the carburetors out front would be to take advantage of the high pressure build up in front of the bike. Instant ram air could be achieved with just the smallest collectors. Having the exhaust on the back of the engine would help it run cooler. With the exhaust in front, all that heat is blown back across the engine. With the exhaust in back, you would just leave the heat behind.

With all that said, I wonder if one could simply rotate the head 180 degrees on say, a KZ900? Rotate your head for increased performance and a cooler running engine. It will look strange for a while. But, the smile on your face as you blow by riders with backwards engines, will have everyone doing it soon.

I believe it is a heat issue. The exhuast portion of the head gets much hotter and having it in the front helps with cooling the head, valves, and pipe. Also with almost no cooling air the hot pipe right under your ass, I mean seat, it would be unbearable to ride. I know that they now use underseat exhaust, but that is only the muffler section, that is relativley cool compared to the header section. The Cannondale dirtbike that was built for a few years was designed as you suggested, and you see what happened to them.

I wonder if it would be a good idea for liquid cooled bikes?

heat of the exhaust would be the first issue,
The "ram" air in the front would not work as well as you think, you draw more air into the intake from the pressure neg and positive areas of the bike, much like a windshield on a car,
remember a engine is nothing more than a vacum pump

Elmer Trett did it in the 70's or 80's and the current top fuel bikes do it too. I think it would be cool for the street. Now that's a project!

I'll try to post a pic in the next thread. Larry McBride used a GPZ head. It has a supercharger on the front and the exhaust goes out the back and exits just behind the rider, pointing nearly straight up. Pretty cool...

Post edited by: 79MKII, at: 2007/11/19 13:00

here you go...

It's been done on Triumph choppers for many years to get a different look. Cooling is the issue, but it hasn't stopped Hardley Ableson.

Within the past couple of months Kevin Cameron of Cycle World magazine did his column on just this subject as to why it isn't really feasible on a street bike.

Bill

STOP stealying my ideas!

i wanted to get an old lay down frame for the track and run a 1000 engine like that, and possibly some late night cruise in's

i'd have footlong pipes blaring out the back :evil:

I guess I need to get out to the drags and read more bike mags. Thanks for all the feedback.

76LTD wrote:

I guess I need to get out to the drags and read more bike mags. Thanks for all the feedback.

Hey, it was definitely a good idea! The fastest motorcycles in the world do it, right?

i posted this question last year and someone found some really cool pics of a triumph that someone had turned the head around on. i'll try to find em

here's the post. i love the triumph pictured!
tinyurl.com/2uwnhd

Post edited by: lunchbox, at: 2007/12/01 13:21