[LiLBull]

any body here ,running on the street or track a full fairing.was wondering about side/cross winds.driving with one on.I do lov ethe look and think its what Ill put on the new cr750 street replica.Besides Id like to hide that wide motor a bit.

Im so far behind ,that I think Im in first.

 

[joe c]

eeesh, thats a can of worms. windage is definitely a problem. but it is even without a fairing. id say the advantage is minimizing frontal area and disturbing airflow off the rear in a specific way. really only useful at speed. id say most guys here, at least for the track dont use a fairing. but i could be wrong. but alot of guys here dont use them cuz they run "short tracks" mostly. there is definitely some advantage to having a fairing on something that will do close to 100 mph in first gear though. (even though thats illegal, right?) then again modern bikes have so much shit to hide under all that plastic. so its kinda 2 fold. for racing, at least vintage bikes, it has as much to do with economics and usefulness, as anything else. something thats going to get crashed alot, or beat up, isnt worth the trouble. especially if its not going to be utilized like at a place like louden where you dont have alot long drafting or where headwinds are a big issue. but then roper has one, turk has one, jb runs one on his "50". but again that is like saying thats why they are so fast. when its not really the case. for the street on a vintage bike, it would be more about looks than anything else id think. and fairings are cool looking.

jc


aaron, send my wheel.

 

[Hoofhearted]

It really is a can of worms. It has been said that a fairing won't help aerodynamics under 70mph but, will add about 4mph to the top end. When I was road racing I would dump the fairing for short circuits but on the longer road courses a fairing was a definite advantage. The only current knowledge of fairing I have is El Mirage dry lake. Its a 1.3 mile run to the lights. My Norton "naked" ran 121.3 and with no changes other than to add a fairing (Peel Mountain Mile replica) it ran 124.9. The only conclusion I can come to is that it does help the top end. Apart from that fairings do look cool. I'd post a pic except I don't know what the hell I'm doing and Geeto has to edit it very time. Ahh what the hell. He's probably sitting in front of his computer with a beer waiting for me to screw up. I'd hate to disappoint him

jc

I meant to say a CB750 would look just too cool with a replica works fairing from the 60s. Espcially with the four meggas in flat black.


Edited by - Hoofhearted on Apr 08 2007 3:39:28 PM

Edited by - Hoofhearted on Apr 08 2007 3:42:43


Edited by - joe c on Apr 08 2007 4:10:03 PM

 

[joe c]

is that your starter? there are people here who might be interested in the details of that thing if you have em.



jc


aaron, send my wheel.

 

[Geeto67]

A lot of old bikes have wind issues but cb750s have notorously bad coefficients of drag. The bike has the hp to pull past the 120 mark in more aerodynamic package but even with a really light rider you can't seem to pull past that because the wind is just holding you back. I am a big guy and with me riding it is like the bike is two up. I can get to 100mph no problem but every mph after that is an uphill battle and the clutch usually gives up first. If i tuck down and put my nose between the gauges I usually get about 110-115mph indicated.

A properly tuned, kitted (836) cb750 making 70-80 hp with a cr fairing (or even better a green meanie kawasaki fairing) should see 135mph -140.

I've seen fairing cb750 dragbikes do 120 in the 1/4 but that is not a lot of room.

something to keep in mind you want a fairing that will blend with the rider. Old bikes have probems with this where there is a gap or the rider sticks out past the fairing. Ideally you want as small a gap as possible between the screen and the helmet, and even a smaller gap between the riders legs and the fairings.

I used to know this drag racer with an gs1100 in a laydown who used to tape himself into the bike with duct tape during tuning sessions. Said it was worth 1-2mph on top end and had the data to prove it. he would tape the helmet to the widscreen and his right leg to the fairing and use the left to inch the bike along. closed up any gap he could.


Edited by - Geeto67 on Apr 08 2007 4:19:09 PM

 

[joe c]

head down on my 550 ive seen 110 on a smooth road. it picks up between 5 and 10 once my head is down. i got scared and backed off. thats with a stock speedo and stock wheels with stock gearing. it was up at redline though so i dont know how much more it really had. nor do i know how accurate my speedo is up at that speed.

also, the 750 seems to be alot taller than the 550. it just seems alot bigger all around. so that would seem right to me. i bet the 750 is really pushing alot more air.

jc


aaron, send my wheel.

Edited by - joe c on Apr 08 2007 4:19:03 PM

 

[jbranson]

I've been giving a quarter fairing a second thought. While skiing this year on some toll roads out in Colorado I was once again amazed at the tremendous difference in speeds if you just tuck down. And we are talking speeds of only around 10 mph. You'd slow to a waking speed standing up...go up to about 10mph in a tuck.
JohnnyB

 

[joe c]

thats a perfect example. never even thought of it but youre absolutely right. do you think the fact that youre sliding versus being pushed makes a difference?

jc


aaron, send my wheel.

 

[Hoofhearted]

Joec, Yes thats what I have to use. Bad knees, 14:1 comp., and 35 deg. fixed igniton prevent me from kicking it anymore. It a Harbor Frieght special. A $12 dolly, a 5.5 hp Briggs and Stratton and some 1" sq. tubing. The Briggs is a fixed throttle motor. What it was designed for I don't know. When I built it I had the(Harbor Frieght) wheel mounted on the crank but it wouldn't grab the rear wheel and spin it. Too high rpm. I took a bit of 1/4" alloy plate that I bolted to the crankcase to carry a 4:1 reduction chain drive. That worked a treat. If anyone want exact details pm me and I'll take some photos and send them. Its really a simple build.

 

[Hoofhearted]

I noticed, with that fairing, how quiet it was when tucked down. Some of the incredibly fast bikes at El Mirage have the hp to run well over 200 but their problem is grip. Drag is the killer. The perfect example is an overheard conversation a few years ago. Rick Yaccoucci was running a 200+ Suzuki. I had run and was waiting to be towed back. Rick ran and pulled in beside me. When his mechanic arrived to tow him back Rick asked "How fast?". His mechanic said "207" Rick "Dang!! I couldn't get it to hook up. It was taching 225". Rick was running without a fairing. With a fairing he could run approx. 10 mph faser. A fairing will help punch a hole in the air and smooth things out a bit. Getting the air off you is just as important. Check out the bike in the background of the photo I posted that Geeto didn't blast me for screwing up. Building bikes is a lot easier than posting photos.

 

[LiLBull]

I was feeling the twin 450 is small width,but when you look at the 750 it looks aggressive do to its width then you have four exhaust in front, wider frame just seems better to slip cover it all in some
glass fairing just to tidy it up aerodynamicly and esthetics are just a huge plus. Think of any exotic car take the body off you have ugly and drag.Pop that sexy streamlined body on and Bamm you have a body for speed and looks when parked.Its what I think the 750 begs for a tailored clothing.

Im so far behind ,that I think Im in first.

 

[UngaWunga]

Reminds me the first time I raced Mosport. Down that long straight, the wind noise was crazy... until you got in someones draft. They it got eerily quite, the rpms would climb, and you'd either have to back off the throttle or pull out and pass.

And that's without a fairing.