I'm thinking about adjusting some things on my carbs while I have them out for another project. MY 97 CBR has a yoshimura pipe, K&N, and a Factory Pro Jet kit. Currently for main jets, I have 140 (out), and 142 (in). Fuel mixture screws are turned out 2 turns. Needle height is set to #4 from top.

The problem is my bike runs great when cold, but once warm has what I think is a rich spot at cruising speed (40 mph @ 4K) It just feels sluggish. Above that rpm and below are fine. It is also fine at that rpm when cold. My plan was to put the needle height at the 3rd position from top and try that. However, I was wondering if I should leave the fuel mixture screws as is?

Thanks in advance

 

Tuning carbs isn't a "Turn xx times" and *bingo* thing. And like I said in another thread: all our bikes have their own unique personalities. Because of maintenance, riding patterns, geographical location and other factors what works for my F3 may not work for yours.

Here's a good guide for tuning your carbs: Carb Tuning Guide - Symptoms and Troubleshooting

 

Before you go and start changing things, I'd put it on a Dyno. That way you'll know, rather than think you have a rich spot, or a lean spot. It's usually less than $50 for a baseline run on a Dyno. Here in S. Florida I can get it done for $40. They make 3 or 4 runs and it shows RPM, MPH, Torque, HP, and Air/Fuel mixture. My wife's F3 was set up just like yours, and it ran much better with a paper filter (oem) rather than the K&N. It had full V&H system (now scrap metal), Factory Pro Jet kit, 142 and 140's, 3rd clip on needles.