hi i have a 1992 cbr600f2 in good condition. it has 18k miles on it and it runs like a champ. i've had it for two weeks now and i ride it easy around the city but on the highway hits 130 likes is nothin. however, when idling after i get off the highway it gets really jumpy and often stalls. also, it does not like to start cold. takes 5-10 seconds sometimes and playing with the throttle. if i start it and ride around she runs fine (for the most part). its mainly after i get off the highway and hit a couple lights. the RPMs are steady at 1400 and every couple seconds jump real quick to around 1500-1550. after it stalls, i wait a minute and when i go to start it again its very difficult to start back up. but after i get it started and take off it runs fine for a little bit then the idle gets jumpy again. but when it decides to run good, the bike starts in 1 second when its warm.. its frustrating because sometimes it runs great and idles great and other times the idle is jumpy and other times the bike just dies at idle.... im thinking its just one cylinder/carb because of the slight jump and how ofter it happens. then sometimes it will just die (especially when im in the city and the temp starts getting up around the 75% mark, but still well within the normal temp)

im going to check the plugs tomoro and the air filter but its just frustrating because it runs so great on the highway and even when im just moving around town. and most of the time the idle is great its smooth and its great but then it just gets jumpy sometimes. i tried opening the gas cap and that didnt help so i dont wanna think its a vaccum problem? it could be a vaccum problem in between the carb and the intake like a loose screw i will check that soon. just looking for any feedback if anyone had a similar issue. thanks a lot

 

It sounds like you are starving for fuel. It could be any number of reasons, but I'd probably start off with cleaning the carbs.

 

ok thank you. do you think it could be as simple as adjusting the fuel/air screw? i cant find that screw on the carbs and can i get to the inner carbs (2 and 3) without a special tool? thanks

 

found the fuel/air screw doubt thats it. fuel pump and petcock are good. ignition maybe? i put in some carb cleaner we'll see if that has any effect..

 

An easy thing to check is the fuel filter.

 

the fuel air screw (pilot jet) is only for 1/8 throttle or lower. After 1/8 throttle, the main jet takes over and the pilot jet adjustment has virtually no effect on the fuel air mix. So if its only happening at ilde and doesn't correct with throttle input, it could be your pilot jet. Also, hard starting is a common problem with a dirty pilot jet, so you may be on the right track.

Generally, adjustments aren't needed to the pilot jet, but cleaning is. If you do decide to clean the carbs, make sure you note where the pilot jets are. Slowly turn them in until they bottom out and count how many turns. This is where you want to return them after you clean the pilot jets. Generally, they are about 2 turns out from bottom. Be careful not to turn them too tight though, just gently seat them. If you crank them too tight, you can damage the needle and seat. You could probably remove the pilot jets and clean them, and shoot some carb cleaner through the pilot jet port. But nothing compares to actually removing the carbs an cleaning them. Be sure to keep them on the rack though. You only want to remove the float bowls, remove the main jet and the air jet, clean them and re-install. Also spray out the bowl and main body if there is tarnish. You may need to use a small piece of wire to thoroughly clean the jets though. They tend to get pretty gummed up with tarnish and its hard as a rock. Just be careful not to use anything harder than the jet itself. a single strand of copper wire from a piece of wire works ok, but it can scratch the jets, so be careful. Also remove the pilot jet and clean that as well.

Its also a good time to inspect everything at this point. Make sure the floats are adjusted properly and the needle and seat are seating correctly.

You mentioned the carb boots, and they can crack after time. You can take some carb cleaner with the bike running and do quick little spurts around the carb boots. If the engine revs up, then you have a vaccum leak in one of the boots. Just be careful as carb cleaner is extremely flammable, use sparing amounts.

Ignition problems usually arise in high rpm situations where its more taxing on the ignition system. Its always possible its ignition related, but it sure sounds like a fuel problem.

 

thank you very much for your responses. so i cleaned the sh*t outta the ground (the opposite end of the negative battery terminal) and i never heard the bike start so quickly in my life. i also put in some sea-foam carb cleaner. the idle has improved and i didnt touch the pilot screw or anything as mentioned above.

but now i have a new problem

(all of this is done while in neutral) if i roll on the the throttle everything is ok but right when i get to about half thorttle the bike nearly dies. if i go slowly its right before i hit 6k rpm. it will nOT go above 6k rpm no matter what. if i try the bike will just completley shut off. if i keep the thorttle there for a second the bike will just turn off. its so weird... im thinking a bad coil? the idle still isnt perfect but its much better and it starts better but now its this throttle issue. i cant even put it in gear and start out because when im releasing the clutch i cant even get enough throttle to get going. so i thought maybe i put in a little bit too much of the carb cleaner. so i put in 2 more gallons of super and still the same thing..

starts fine. idles better. but now i cant go near or passed half throttle. bad coil????

oh and as far as fuel goes, i took the fuel line off and pressed the Start button real quick and plenty of fuel was coming out. full pressure. so the petcock and fuel pump seem to be good. so i rueld that out.

i doubt its plugs because all 4 would have to be bad, the bike is just compeletely dying. so im leaning towards bad coil. any suggestions? im actually going to go test the coil and see what omes reading im getting. (taking this fuel tank off for the 10 fuc*ing time today...)

 

oh and where the hell is my fuel filter? i cant find it anywhere and i cant find it anywhere in the service manual.. anywhere.. its not in the fuel tank (i dont think?) because gas flows when i took the petcock off. and its not in the petcock thats just the fuel pump. then the fuel just goes to the fuel line..so where the hell is the fuel filter

 

coils are both good. throwing 3.4ohms or resistance between the terminals... now what

 

the manual actually says 2.5-3.1 and mine are both throwing 3.4. theyre a little warm tho because the bike was running about a half hour ago. normal or is that too much resistance?