CBR600 F2 road/race project info needed
 

Hello. I need some info (probably a lot of people have or are still racing on these F2s) about engine tuning :

I have a heavily modded F2 with USD forks, VFR Swingarm and I would like to focus a bit on the engine this year and finish my project. I cannot buy FCR carbs because they are more expensive than a 600RR.

I need info about F2 carbs - how to get the most of them. Is it better to change to F3 carbs ? Modding the Air box to allow Ram-Air / Cold air intake will help or not ?

On exhaust system - I need some info if anyone has done his own exhaust system from headers to slip-on? I have a welder I can use but will need some measurments. I can buy one from the USA but shipping is too much so only EU is left as an option.

I read that putting F4i cams increases horsepower and +2 ignition timing.

Anything would be helpful. Thank you in advance. I have read most of the topics here but most do not provide sufficient info or are just incomplete.

First of all, welcome to the forum. I see this is your first post. Where are you at? Where do you plan on racing? What racing classification allows the VFR swingarm on a F2?
F3 ram air could be adapted to the F2 with enough determination, dialing in the jetting would be a major pain in the rear I'm sure. I doubt the F3 carbs would make a difference. Probably better off with factory exhaust and aftermarket muffler, unless you were an exhaust builder/engineer with access to a dyno so you could try different designs etc etc. With the "off the charts" homemade exhaust you could be losing horsepower instead of gaining. As far as cams go, the F4i intake cam in place of the F2 intake cam and then take the F2 intake cam and use it as the exhaust cam. You probably wont be able to feel more power but the snappyness/throttle cripsness would be better. And you'd need slotted/adjustable cam sprockets. Alot of people like the ignition advancers.
It sounds like you did some serious mods to your bike with forks and swingarm. But I'd be willing to bet the farm that the original forks with springs and oil for your weight and original swingarm with a Fox or Ohlins shock set up for you would get your lap times down more than the USD forks and VFR swingarm.

Thank you for the welcome. We race for fun mostly - It's too late and too expensive to go in championships and F2 is quite old for that too. The reason I changed to usd forks was to have more setup options and better brakes - the 2 piston calipers just don't do much when it comes to braking.
The bike has now
GSXR750 K1-K3 Front USD Forks - upgrading to radial soon (either change the fork bottoms or change both forks)
Wheel is from SRAD750 with 320mm discs - cheap to get, a lot of aftermarket brake disc options. Using TRW sinthered patds.
VFR Swingarm was done because I liked how it looked. I could have gone with just 900rr rear wheel to use 180 tyre but I am happy how it turned out. With these mods the bike cuts corners and is responsive. Nothing in common with the squishy F2 suspension. For the rear shock I am opting for either 954 shock (mods to fit it) or gonna browse around ebay for a fox clicker.

Thank you for the much provided info - I will stick with the F2 carbs then and try to make some air intake.
I know that making an exhaust needs engineering skills so that is why I am after some measurments from an aftermarket one or will just wait for one to pop up.

I am located in Bulgaria - Eastern Europe. Mostly browsing ebay.co.uk, ebay.de , ebay.it :D


https://scontent-otp1-1.xx.fbcdn.net...12&oe=5904FAEFhttps://scontent-otp1-1.xx.fbcdn.net...9a&oe=59063300

The ram air mod, you just dont make a big intake for the air box. The float bowls need to be pressurized. If not the ram air effect will be trying to force the fuel back into the gas tank. F3s had fuel pumps to help offset this effect along with small tubes that was hooked to the ram air. Probably way more trouble than its worth and the only time it will actually help is when you going over 100mph probably. I appreciate your enthusiasium to build your own exhaust but.........If you dont have access to thin wall exhaust pipe and use regular pipe you'll be adding a ton of weight, offsetting any benefits.

Well KokoVmax did his with a tube welded to the front. I am prolly gonna try make use of the original F3 airbox or just low my radiator a bit and put two pipes above it - will try to make it possible to adjust the air income until i get it right. I have time and I can test it at the track.

About the exhaust - yes we have access and I have a welder who will make it cheap but I just found one on ebay today - MOTAD exhaust system - and will prolly buy it by the end of the month :)

I dont believe Koko's ram air was a "real functioning ram air" for the simple fact that it was never shown to be a completely sealed system inside the frame perimeter, on the other side of his homemade intake snorkel. Plus I didnt see in the pics all the hoses that supposed to pressurize the float bowls. Koko's system provided lots of cool fresh air but not "ram", very similar to the F2 original factory set up. See the two hole in your frame in the pic, thats where the air passed to the air box area from the factory fairing. The factory fairing had intakes molded into it with a tube directing to those holes but by no means was it considered ram air. And all Koko did was make fancier holes through the frame basicly.

Well actually on the F2 the air passes just above the radiator in a weird way - the air box has tubes curved down to the radiator and that is why sometimes it takes hot air from the radiator like in the picture - this is looking at the box from the top. He just rerouted the air intake so that it takes cold air when moving. :)

http://img.auctiva.com/imgdata/1/2/1...54184314_o.jpg

I tried putting ram air on an F2 back in the 90's. It was tough. Not worth the gains. You would only gain power at high speed, and you would probably gain much more (than ram air) if you put the front upper fairing back on. Naked isn't slippery, and that matters once you pass about 50 mph.

Well actually the F2 intake air is not suppose to go through the top or over the top of the radiator. There suppose to be a piece of rubber that keeps the hot radiator air from going into the air box. The intake air is supposed to come from the holes in the frame like I explained earlier. If that rubber piece isnt there your losing horsepower because the air is heated. Thats why the air comes from those holes in the frame that has been directed there by the factory fairing.

You say "he just rerouted the air intake so that it takes cold air when moving". Well guess what? That is not ram air. And just FYI a original F2 has cold air intake, not hot air intake like you said.