Semi-pointless tech Q about MC engines - Kawasaki KLR 650 Forum
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post #1 of 9 Old 02-11-2010, 03:26 PM Thread Starter
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Semi-pointless tech Q about MC engines

For over 100 years, motorcycle engines have literally always had the
carbs behind the engine and the pipes sticking out of the front.
(This much we already know.)
Since high school, one of my buddies n' I had wondered about the whole ram-air thing on the musclecars of the 60's-70's and why, why, why don't bikes
have the carbs out front with cool fresh air getting crammed in them at speed? The natural vaccuum behind a forward traveling MC would greatly help exhaust gas scavenging too.

I'm still wondering 25 years later why don't the rockets especially have a huge scoop feeding the carbs or injection tunnels right behind the front wheel?
Obviously the pipes are curved back both for scavenging and to keep hot pulses from cooking us on hot days.

The only real answer we could ever come up with is to keep the entire engine at a relatively constant temperature throughout the block. The front/ intake would be MUCH cooler than the rearward facing exhaust valves and headers.

So why not get a turbo effect for free when at freeway speeds?

Enquiring mind(s) wanna know. Plus, it would look kinda cool on streetbikes with a big, gaping chrome shark mouth/ funnel behind the forks.

Thanks in advance to any techies with real world knowledge who wanna take a stab at this, or novices on engineering like me who wish to take an educated guess in the dark at why.

CheapBoredAndCuriousWithCabinFever
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post #2 of 9 Old 02-11-2010, 04:20 PM
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I got no idea (maybe cause the wheel kicks up water/grit/etc?), but, if I haven't mentioned it, I have been plagued with a Q lately, too. It has been gray and rainy a lot. Why don't cars' headlights automatically run all the time like MC's?

Bonus Q. (sorry)




"In a car you're always in a compartment, and because you're used to it you don't realize that through that car window everything you see is just more TV." R. Pirsig

PPMC #1.
Soon, we ride.

AKA JD Mader or you can call me "Dan" just not early for dinner.

Click my handle for a link to my homepage/blog...which has nothing to do with MCs. Free literature and music! Viva La Revolucion!
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2008 KLR 650
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post #3 of 9 Old 02-11-2010, 04:50 PM
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I saw one done that way, at the Seattle International Raceway drag strip in the early seventies. A small low slung three wheel trike/cart type thing with a Kawasaki 750 triple engine with the cylinders on backwards, the carbs right behind the rider's head, three expansion chambers pointing straight out the back. Big wide but low back tires, motorcycle front end. I don't remember the times he turned, but he smoked everything but the funny cars and rails, and they didn't beat him by much. Something like maybe a six second quarter mile?

Seems on a production motorcycle there would not be space behind the front wheel for an airbox and carbs.

The way the modern inline four bikes are with the carbs on top of the head and the airbox where the tank should be is pretty close.
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post #4 of 9 Old 02-11-2010, 04:57 PM
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I saw several guys running Yamaha TZ250 roadrace bikes in the late 70's with reversed cylinders for the obvious "benefits" that it would afford. Problem is that carbs need smooth airflow coming into them. Having them out in front with velocity stacks would cause all kinds of problems when drafting another bike or side winds came up. A carb actually works very well in a box. Ram air isn't all it's cracked up to be unless you can make sure you always have smooth air coming in. Good question though....

John

Farkled probably WAY too much, but good 20' footer for sure. '96 KLR, '06 HD VROD, (girl friend hauler), '05 HD Electra-Glide, heh it's a HD and I'm old now ;-) and I'm proud of riding a 800+ pound bike at my age :-)
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post #5 of 9 Old 02-11-2010, 07:25 PM
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I have a question too....


at what point do Flys turn over and fly upside down to land on the ceiling?

- Joe

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Quote:
Originally Posted by larryboy
come awn... it's not far...it'll be fun..

sorry I can't....... I'm fishing today
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post #6 of 9 Old 02-11-2010, 09:03 PM
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Quote:
Originally Posted by Lockjaw View Post
I got no idea (maybe cause the wheel kicks up water/grit/etc?), but, if I haven't mentioned it, I have been plagued with a Q lately, too. It has been gray and rainy a lot. Why don't cars' headlights automatically run all the time like MC's?

Bonus Q. (sorry)
they do in Canada. since about 1996 manditory from the dealer. you just gotta get your country in line and conform to the greatness of canada. and adopt the metric system while u are at it. (i know u have a 10mm wrench in your tool kit, lol)

02 klr - heated vest and grips, corbin dished, EM doo, petcock mod, MB PCV mod, stainless oil filter, bash plate, mayher hand guards, low mount fender, power socket, tall windscreen, jardine exhaust, jetted, studebaker shifter, magnetic plug, airbox mod, k&N, kenda knobbies, DIY pelicans, HID light
96 zx11 - bone stock - saving for a collector plate
2011 BMW f800 GS - [email protected] crash bars, altrider skid plate, barkbusters, kako, aeroflow med, heated corbin, wolfman, kenda big blocks
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post #7 of 9 Old 02-11-2010, 09:07 PM
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Quote:
Originally Posted by doc3toes View Post
they do in Canada. since about 1996 manditory from the dealer. you just gotta get your country in line and conform to the greatness of canada. and adopt the metric system while u are at it. (i know u have a 10mm wrench in your tool kit, lol)
Dude, if you only knew how much I agree with this. I contemplate moving to Canada on a regular basis.




"In a car you're always in a compartment, and because you're used to it you don't realize that through that car window everything you see is just more TV." R. Pirsig

PPMC #1.
Soon, we ride.

AKA JD Mader or you can call me "Dan" just not early for dinner.

Click my handle for a link to my homepage/blog...which has nothing to do with MCs. Free literature and music! Viva La Revolucion!
-------------------
2008 KLR 650
RIP DM - Soon, we ride.
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post #8 of 9 Old 02-11-2010, 09:10 PM
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Quote:
Originally Posted by doc3toes View Post
(i know u have a 10mm wrench in your tool kit, )
I use a 3/8ths wrench I smashed a lil with a hammer to make it fit tighter.

- Joe

HighSpeed Hiker- DV o5'
Quote:
Originally Posted by larryboy
come awn... it's not far...it'll be fun..

sorry I can't....... I'm fishing today
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post #9 of 9 Old 02-11-2010, 09:19 PM
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Quote:
Originally Posted by theotherbigjoe View Post
I use a 3/8ths wrench I smashed a lil with a hammer to make it fit tighter.
hummm, are u sure that isnt your foreign affairs policy? smash it until it fits, lol. Joking, USA is a great big brother.

Not to hijack this thread ....

If you do a search for 'ram air superbike' you get all kinds of stuff on the zx bikes and the hiabusa. This might really make me seem like a tard, but my zx has 2 openings in the front farring that are 'ram air intakes.' honestly i dont take my ninja apart (even though i have the KLR stripped to the bolts). so are these really ram air systems or not?

02 klr - heated vest and grips, corbin dished, EM doo, petcock mod, MB PCV mod, stainless oil filter, bash plate, mayher hand guards, low mount fender, power socket, tall windscreen, jardine exhaust, jetted, studebaker shifter, magnetic plug, airbox mod, k&N, kenda knobbies, DIY pelicans, HID light
96 zx11 - bone stock - saving for a collector plate
2011 BMW f800 GS - [email protected] crash bars, altrider skid plate, barkbusters, kako, aeroflow med, heated corbin, wolfman, kenda big blocks
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