www.zxrworld.co.uk

my bike has a "hickup" at about 4000rpm when using a neutral/part throttle,and a backfire at 8000rpm when coming down on a closed throttle,is this normal?
i've balanced the carbs,the plugs are a dark brown,so i thought it might be running rich.where is the mixture screw?
sorry to be full of questions.

dark brown wont be running rich, should be black/sooty if it was.

a tan like colour shows perfect mixture.

is it a proper misfire or more of a flat spot?

a sort of stutter,thinks about accelerating,then goes,it's doing my head in.
the plugs are very dark brown/black

Id say check the air filter but if the plugs are ok then maybe not. Might be worth checking it anyway as backfire tore mine apart on my first ZXR. Cant remember where the mixture screws are, think they are located inside really short pipes on the back of the carbs. Can always borrow my CDI if you want to eliminate that mate.

i drainded the carbs of all the fuel,my god,full of rusty/brown/dirty petrol!!!!
run a little better now but not perfect yet

until 4k rpm my bike doesn't consider doing any accelerating at all.

zxr400s shouldn't be run at less than 10k revs anyway.

never used to let the rev's drop below 4k, even when warming up it was kept around 4-6k the engine just dosnt have anything below 4k

that'll be why then,lol.
got to find time to strip/clean them,cheers for the advice guys

I try to keep my revs above 4k, seeing as thats when the altenator output peaks at.

stripped and cleaned the carbs,wow,full of rusty looking red "goo",ran the bike out today and much better,
theres still a pause/stutter at about 4k but i can only assume thats normal as its 19 years old/carb fed
(compaired to a 04 636)

try runny some redex through mate, thatll clear any toad that might still be in there, out.

i'll try the "one shot" redex.

yep that'll do, 99p at halfords

1.49,i was robbed!!!!lol