Run for cover... Another Jetting Question!

[PitterB4]

I know that carb questions from novice wrenches like me get old but...

I've mentioned here several times that, when it's cold out, my B4 has a bad flat-spot in the 4-5k range.  It got way worse when I went to my modded airbox (which I have since removed and gone back to the stock one).  So, I figure I'm lean on my needles and raise them one notch.  The flat-spot is gone but now I seem really rich - lots of tailpipe soot and it seems to bog every once in a while if it's warm and I'm cruising at that same rpm range (<1/4 throttle).  So, my thought is that I could drop the two inside needles back down and leave 1 and 4 where they are - thinking that the inside cylinders don't get as much cooling and run hotter and therefor need to be leaner.  Does that make ANY sense or am I way out in left field?

Before I do it, I'll pull the plugs and have a look at them but I was just wondering if this was at all reasonable.  I'd love to get on a dyno with a tailpipe sensor too but I don't think I'll have an opportunity b/f the rally.  

Any and all help is appreciated!!!!!!!  

[gsxr400 racer]

insides run leaner because of less air ne to be richer how about a washer for a half a needle raise.

[Thief400]

Rob have you changed your thermostat to get your engine running at a consistant temp.

[PitterB4]

Rob have you changed your thermostat to get your engine running at a consistant temp.

Nope - what would you suggest?

[terrebandit]

I've never heard of anyone who has staggered the needle settings (diff clips) before but I suppose that it might work.  I can't believe that there would be that big of difference between your carbs.   I would add a shim (half a step) to the leaner running cylinders and see what happens.   It is common for guys to stagger the jetting (i.e. main jets).  The inner cylinders run hotter and therefore can take a slightly larger main to make them run cooler.  If your headers show a pretty even color, that would indicate that they are running about all the same temp.  If you have a couple blue pipes and a couple gold pipes, I would consider doing what I suggested above.

Dave

[PitterB4]

Thanks all...  Dave - North American B4s have black coated pipes so, mine are all the same color   .  

An update:  I rode to work yesterday.  Going home (first 80 degree day of the year - 50 mile trip), it was really bad stumbling all over itself.  I had to run a gear lower to keep the RPMs up above that range.  Assuming the plugs all look about the same, I'm just going back to the middle postion and put-up with the flat spot when it's cool out.  When I get back from the rally, I'll play around with the modded airbox, larger mains and different clip positions.  Right now, I just want reliability for the rally.

[interfuse]

I just put in 110 mains, with middle clip position... I'll let you know how it goes if my petcock ever arrives.

[PitterB4]

I just put in 110 mains, with middle clip position... I'll let you know how it goes if my petcock ever arrives.

What other perf mods do you have - exhaust, airbox, air filter, jet kit...?

[interfuse]

Full Yoshimura exhaust, K&N air filter and jet kit (I think, it was installed when I bought the bike had 97.5 mains in rather then 102.5 that where stock).

I haven't tinkered with the air box.

[Bandit]

On my old gsxr750, there is a flat spot in the 4K rpm, the problem turns out to be the worn emulsion tube, I have to keep dropping the needle to solve the problem, eventually I decided to junk the dynojet kit and put back the stock jets.