Has anyone opened their pilot screw a notch (say an 1/8 to 1/4 turn) on each carb to improve cold starting and slow speed riding.

The reason I ask is that my bike runs a bit shaky at slow speeds in first gear. I corrected this problem on my Honda VTX1300 by doing just that. It has a fuel enricher (vs. a choke) which tends to foul the spark plugs, so opening the pilot screw fixes the problem. They tend to make the bikes run a bit lean out of the factory.

I'm not sure if I can make the same assumption with the four carburetor CBR.n

 

I can't speak to this, as I didn't receive my bike with a stock setup. Some goon took the carb screws out to 4 turns to try and compensate for the filter and exhaust they slapped on. They had no idea what they were doing.

I have heard however that a jet kit isn't needed to make these bikes livable. I've heard something as simple as shimming the needle up a bit helps

 

That's really interesting because that's exactly what I did with my single carb VTX. There's something a lot of VTX owners do known as the SCAR method (named after some guy) where you shim the main needle with a small washer to tune the carb after installing an aftermarket airbox and pipe. We also open the pilot screw a bit regardless to make it start and idle better.

I just wasn't sure if the same rules applied to the CBR. If so, then probably shimming the needle isn't necessary because although I have an aftermarket pipe, just changing to a K&N filter isn't considered opening the airbox. The plugs looked a pretty good tan colour too, so I don't think it's running lean at the needle.

The bike actually runs pretty well at all throttle positions except slow speed and it's not even that bad, just a bit bothersome.

With the VTX, once you change the airbox and pipe you have to either shim the needle or install a bigger one, or your carb will be starved for gas.

 

When you adjust the screw does it make your MPG worse?

 

I haven't adjusted it yet on the CBR, but I believe the change in mpg would be minimal with just a pilot screw adjustment. If you put a larger main jet in than that could definitely decrease mpg.

 

Not always. On my bike rejetting gave me better fuel effecient. My bike was overly lean and therefore required wringing it out to just get it moving. Lots of wasted fuel for no power delivery. Rejetting helped significantly. Also, leaning out my pilot mixture that was way off helped. You'd be amazed how much difference the pilot mixture can make over the course of a full tank of gas!

 

Ok, so I finally got around to removing the left side panel so I could access the 4 pilot screws, albeit, the #4 carb screw would be easier to get at from the right side.

Nice thing with the CBRF2, the pilot screws take a simple slot screwdriver to adjust, as opposed to the stupid d-shaped tool required for later models.

I screwed each one in to the set point and unscrewed it to 2 1/4 turns (I'm in Canada - stock setting is 2 turns) and what a difference.

I have a lot of experience fooling with the single carb on my VTX1300, but was hesitant to do the same with the 4-carb CBR. The result is nothing short of impressive: better idle, better low rpm torque, and seemingly better performance overall.

It would appear that Honda tunes the carb slightly lean (emissions control?) like all of their bikes.

My recommendation is that if you are having an issue with rough idle, poor starting and lack of low rpm (2-3,000 rpm) power, consider a 1/4 counterclockwise (in addition to stock specs) turn of your pilot screw.

Based on the performance, I would say I got it right. Spark plug analysis (yet to be done) will confirm.

Performance at higher rpm seems to be good. My next step may be to shim the main jet a bit with a washer, but only if I can get more air flowing into the carbs.

 

that will improve low speed riding and cold starting..i did it on bolth mine...