I have a 1991 1000F, I removed my airbox and put on 4 K&N filters, the bike starts and idles fine, so I took it for a ride about 30 min. of stop and go in new mexico heat she dies at a light while ideling, starts back up and I am just carefull at every other light not letting her idle down, then about 1 hour later shile driving the freeway for about 30 min seems like she has no lower power have to shift down and acually ride at a slow speed, or constantly change my speed, every time I try and keep a constant speed for to long a get sputtering..
Could I need to rejet, is it from the crank case breather not being conected I just left it open, should I block it off. like I said high end power she good, low end power is severly lacking

 

Well the first thing you should do is throw those K&N filters over the nearest fence - these bikes don't like them, much better with the standard airbox, and fit a K&N single cartridge filter. The turbulence inside the fairings is something they don't like.There's also too much heat inside the fairings to run the little filters.
Not sure what else is wrong - hard to tell from here, but reconnecting the breather is a good idea.Replace your airbox and see if the problem goes away - I think it will.

 

great ideas, but my bike is a streetfighter no fairings, and the airbox is sold to the highest bidder which wasnt much, Ya this bike runs hot REALLY HOT always has, maybe ill have to build a heat shield or a custom airbox type thing, thinking with the free flow of air going to have to rebalance the carbs and maybe do a rejet.

 

ok so i havent tuned the cbr yet...im not running the air box either...but im running a intercooler...but i have done this on a suzuki katana 600 that was converted to a fighter which everyone says it will never work...it takes a bit of tuning BUT you can get it to work..most want a drop in kit but your never that lucky...your problem is when it gets out of the idle circuit its soo damn lean its just going to bog....im not certain what its running for stock jetting...or if you have a jet kit in or what....what i had figure out on my katana ( i had a dynojet kit in that) the stage 1 jet kit had which the largest jet was a 118 which i had went and got a few different jet sizes and ended up buying a 134 for the out and 132 for the inner carbs and lower the needle one clip

based off my tuning the carbs on the katana if you did say buy a dynojet kit and put it in..this is basing this off of my personal experience if you bought the stage 1 kit you would require a jet of 134 for your inner carbs and 136 for the outter carbs, but i would buy 4 of each 130 to 136 for tuning

of course this is be basing this of of personal experience

 

well the reason i say to run a smaller size on the in's is because stock they do the reason they do this is because the inner cylinder heat faster which you want a even heat across the board and i did a look on dynojet's site an they say without the airbox you need to run jets in the 140 range

 

Sounds to me like the engine vacuum isn't right, and isn't keeping the petcock open. So the engine is starving for fuel. I've never put a vacuum gauge on it to see how much it needs to open the petcock, but it's probably not that much. To bad our CBR's don't have a petcock with a PRIME position that just lets the fuel flow.

 

Ya great advise all...Now I need to begin my search for the jet kit, I was figuring it would need to be rejetted after I noticed the problem, was hoping to run into someone that had done this mod, I guess I will keep posted and maybe a write up after I get it all figured out, was also thinking vacuum but it all worked great before the mod, wasnt sure about the crank case breather hose going into the airbox had anything to do with it.

guess how much the highest bidder was for my stock airbox with the K&N filter.........10.00 smiley face slapping himself