www.zxrworld.co.uk

I've got a zxr 400 and it's been off the road for a while, recently got it back running again and it runs fine up to 5000revs but then Boggs down all the way up to 10000revs and then it will go like f*** after it's got past 10000 revs, it will rev up fine all the way through when it's in neutral or when the clutch is in so the fault only happens when the engine is under load, I have had the carbs off and given them a clean but starting to think for what it's worth I may as well have them off and clean again. I've spoken to a carb specialist and he doesn't think adjusting the carbs will solve it, the spark plugs have all got a spark and have been out and cleaned but I do have new ones to fit. If anyone's came across this fault before or has any ideas to try any input would be appreciated thanks.

Buy some m3 washers from ebay, fit 2under each carb needle to richen the midrange and let us know if that fixes it.

A good carb strip down sounds like it would be in order, does your problem change if the bike is cold or warm?

I'll try cleaning it and if I get no luck I'll give that a go thanks, no it's the same wether it's hot or cold.

Fitted all the new parts (fuel filter, spark plugs and battery) it runs better but still not right, if when I ride it I put the choke on it will run as it should but obviously cut out when I come to a stop. Really stuck with where to go next, any ideas will help.
Thanks

if it runs better with choke on at idle then you need to richen your 4 mixture screws (screw them out counterclockwise at 1/4 turn increments and test the result).
if it runs better with choke on between 5-10k rpm then your midrange needs to be richened (use the M3 washers to raise the needle height).
if it runs better with choke on from 10k up to redline then you need larger main jets.

what exhaust/downpipes/airfilter have you got, what are your mixture screws currently set to, what are your float heights set to, and what main jets are you currently using?

if your floats are too low you are going to get lean symptoms across the mid to high rev range, alternatively you might have an air leak between the carbs and the engine. what is your idle rpm set to, and when was the last time you balanced the carbs?

During going to fit washers went Into more depth of cleaning the carbs while they was off, took the jets out and found a bit of gunk in one of them, I didn't fit the washers as I was sure this would solve my problem, put it all back together and it seems to run fine. Thanks for your help