www.zxrworld.co.uk

Hi folks scratching my head here as I am no bike mechanic, I am going through another mid life crisis and decided to buy myself another zxr 400 ,it has serious issues running ,when I got it ,it spluttered like mad under 5000 rpm so took it to our local bike repairer ,he took the tank off and the carb rubbers and clamps where really bad so he replaced them ,got the bike back and it's worse than ever ,it's hard to even keep it going ,cuts out when warm at every occasion ,absolutely gutted .any advise would be gratefully received ,by the way it's an l1 model but for some strange reason has no overflow res on the side ?
Thanks people

Does it idle ok? I would check all of the carb settings and set it back to standard, does it have any modifications? Exhaust or filter?

Hi mate yes it has an after market can ,a jce carbon can ,not sure what jets should be in it though ? Idles on choke ok but when warm cuts out ? Thanks for your quick reply

How do I find out what jets it should have in please ?

For a k&n filter, desnorkeled airbox, aftermarket downpipes and straighthrough can K&N air filter, sandy bike spares downpipes and a straight through can with a de-snorkled airbox still with the top silencer cover (i think it helps to stop rain getting in the airbox.

pilot air screws set to 2 and 3/4 turns out from fully in - any less and i need a touch of choke to fire up, any more and i can smell unburnt petrol on tickover.

pilot jets - K35 as standard

needles, N77S (standard) but with 3 shims underneath to raise the needle by ~1.5mm - this means that the needle doesnt block the fuel path quite so much throughout the midrange, you can test this by seeing how the bike pulls from 3k - 6k rpm in ~3rd gear and see if you need more/fewer shims, i wouldnt go for more than 5 as a guess judging by the look of the DJ needles.

float height - all set to 11mm (standard)

mains, running 100's i still needed choke so i went for 105's and it flies! you test this as you were doing by opening the choke at wide open throttle and >8k rpm in mid range gears (3rd) and checking to see if your bike picks up (still to lean), boggs down (ok to slightly rich), or does nothing (slightly lean to ok).

Wow thank you ,I'm no mechanic but I'm sure my bike garage will know what you are on about ,apparently it's an import bike but with uk carbs ? Does that make any sense to you ? Thank you

Yeah but shouldn't effect it as such, you can look at the carbs yourself, its not too difficult and it will save you some money and learn as you do

http://m.youtube.com/index?&desktop_uri=%2F

Have you thought about new plugs?

I had a similar issue once.

To be honest no I haven't ,is there any you could recommend please ?

ross46 wrote:For a k&n filter, desnorkeled airbox, aftermarket downpipes and straighthrough can K&N air filter, sandy bike spares downpipes and a straight through can with a de-snorkled airbox still with the top silencer cover (i think it helps to stop rain getting in the airbox.

pilot air screws set to 2 and 3/4 turns out from fully in - any less and i need a touch of choke to fire up, any more and i can smell unburnt petrol on tickover.

pilot jets - K35 as standard

needles, N77S (standard) but with 3 shims underneath to raise the needle by ~1.5mm - this means that the needle doesnt block the fuel path quite so much throughout the midrange, you can test this by seeing how the bike pulls from 3k - 6k rpm in ~3rd gear and see if you need more/fewer shims, i wouldnt go for more than 5 as a guess judging by the look of the DJ needles.

float height - all set to 11mm (standard)

mains, running 100's i still needed choke so i went for 105's and it flies! you test this as you were doing by opening the choke at wide open throttle and >8k rpm in mid range gears (3rd) and checking to see if your bike picks up (still to lean), boggs down (ok to slightly rich), or does nothing (slightly lean to ok).

this is my setup for my bike, expect yours to be slightly different, but in a similar ballpark depending on airfilter/downpipes/can

things to check:-
battery
spark plugs
ht leads
coils
if not then its probably carbs, pull the jets and make sure they are clean - the pilot jets have a very small central bore that easily gets clogged up with dirt/stale fuel, then set the pilot air screws turned further out than you previously had them, say 1/4 or 1/2 a turn and see what effect that has.

as for plugs there are 2 main types, double electrode CR9EK and iridium CR9EIX, ive used both, and i prefer the CR9EK, plus they are a fair bit cheaper.

i think you can also use the single electrode CR9E...but im not 100%, and i think it would perform worse than the double-electrode.

You can use the cr9e without problems apparently. But since cr9ek are the specified type stick with that.

My plugs were quite old and were breaking down.