Hey, I've played with many-a-carb before, but never rejetted one...

Instead of buying new jets, could I not just take a very small set of drill bits and carefully bore out the holes in each jet one size bigger and test each time until the bike runs smooth?

Any opinions and experience with this is welcomed, unless you dont know wtf you're talking about!

 

Don't ever do that.Jets aren't that expensive individually.

What's on your bike now?

My F2 racebike had the clip in the top position,one carb needle shim underneath the clip.40 pilot jet (stock is 38) ,122 main (stock is 132,I think).Paper air filter,ran awsome and made 88.7hp on an eddy-current dyno on pump gas.I had this done at shop here in Atlanta,and went out and whooped ***!! (til the motor finally gave up,after 13 years)

Oh oh oh.Almost forgot.You have to get the air mixture screw adjuster right also.That I haven't looked at yet (maybe this weekend).I have to make a tool for it.It's the d-shaped thingy on the bottom of the carb.

I'll let you know as soon as I do

 

Bike started to run like poo when I cut andstraightened the air box intake tubes, and put an aftermarketslip-on muffler on.

Strangely enough though, I used to get 200KM per tank, when I got new tires, chain and sprocket I lost 20KM off my tank and started to only get 180KM.

Now, since I've added the pipe and airboxmod, I've lost another 20-30 km off my tank and I'm hitting reserve around 150-160!

How the heck can I lose 40-50 km's per tank fuel efficiency with new tires, chain, sprockets, pipe and airbox mod??

I thought good tires were supposed to improve fuel efficiency, changing the sprocket sizes to +2 on the back and leaving the front stock would reduce it a little but not 50 km/tank.

Changing the pipe and airbox would make it run LEAN which means LESS fuel! So I dont know wtf is going on...

I do need to be re-jetted though

 

Not quite.On paper or in theory,yes.

These bikes need efficiency to get the most out of them.Car math won't always work.

Put the airbox back like it was.Make sure the rubber thing is in place also (it's what is in front of the snorkels on the airbox).

Stock gearing works everywhere.Revving doesn't hurt these bikes,as long as it's under load.A 520 chain and sprocket kit will help you with what you want.

New springs in the carbs will help too.

What tires are you using?

 

Metzeler Sportec M3's, stock F2 size.

I got a bit better throttle response out of the bike by shortening the snorkels, the way they are stock pulls air from a relatively dead area... cutting them right down forces more air into the airbox.

I'm not an engineer or anything but it just makes sense to me that this would be better, I was told to do this by somebody with much more experience than myself that also raced an F2.

It's not my intention to tell you you're wrong, I just dont feel that's the cause of my problems, I appreciate the help!

I prefer the gearing the way it is over stock, I could care less to do 250 km/h, how it is right now is perfect for the riding I do (very twisty technical roads)

Carb was rebuilt recently, so springs and gaskets etc are all good...

 

Put an ega snorkel on it,I bet it's way off.

The airbox snorkels pull from an area that is less turbulent.On the F2 the air will push outward on the bodywork and screw up the airflow when you get higher in the rpms if you don't use the rubber shield.Moving the airbox snorkels messes it up also.

My racebike was like this.I straightened it all out and it ran better,the ega snorkel doesn't lie.

 

I think the L shape in the snorkel slows down air flow and also causes turbulance inside...

Can you get a picture of what you changed on yours?

I still have my rubber shield installed, but the airbox now looks like this:

http://img524.imageshack.us/my.php?i...1170972lw0.jpg

http://img524.imageshack.us/my.php?i...rinsidezr5.jpg

My theory was that more air would be crammed into the airbox, and the long tube pertruding inside the airbox was holding the air inside longer than necessary so cutting that off made the air more readily available.

I'm an amature and I have no high tech testing devices so I could be wrong, but it makes a sweet sound and I did notice a bit more crisp response so who knows!

 

The opposite,actually.Your airbox is pressurized.The only time you remove/mod the airbox is to install flatslide carbs.And they are a pain in the ***.I had those too [:@]

That's with your current jetting.Remember your gas guzzling problem?

Mine has all the stock parts on it.Paper air filter too.The more of the former racebike carb pieces I install on the streetbike,the better it runs,much like my F2 racebike did.And it was perfect.

My racebike now has an F3 motor in it.


I spent alot of money learning this....

The guy I bought my F2 racebike from had "modded" it in several ways.He swore it was fast.I took him at his word.Uh boy...........

It ran ok,but I started noticing "un-Honda" like things happening while riding it.I popped it open and there were mods done that I thought would do well for the bike.Then it started running "funny".Not bad,but not proper either.

I ran the bike down to MSP Cycle here in Atlanta.The questions I got were" Where's the rubber thing?" , "Still got the stock snorkel?" , "This f*cks up your top end" and so on.I went and got the stock parts for them.I said "Fix it" and then left.


Of course I had to know what they did.They showed me the dyno runs and why what they did was important,and I'm relaying it to you here.The jetting is listed above.Picked up 1 1/2 hp and a smoother powerband.All the stock airbox pieces were back on the bike.Off to the next race I went.

The bike ran really well and was easy to ride.Didn't fight it at all.And the flatspot @8k was gone,and so was I.All stock motor and carbs my friend.Got my first win of that year.

 

Alright, thanks... I'll revert my airbox and see what happens.

With my aftermarket exhaust will I still need to rejet?

 

Yes.

The jetting is listed above for a Two Bros full system after being ironed out.I'm moving all the carb internals over to the street bike,and as hoped for,it's running better and better.

Bets of luck and keep us posted on your progress.