Confirmation of Diagnosis?

[Columbo]

Hey all.

Having some issues with the ZXR. I've had a think and I'm fairly certain I've diagnosed everything but I'd like to hear your opinions before I take it into the workshop and ask them to un-f*** it.

Revs hang at 2.5k RPM
Get 70 miles to a tank
Massive flatspot below 5k RPM

Carbs were balanced by a local workshop since I didn't have the equipment. I think they may have set the mixture screws wrong and this is the cause of the issues.

Any thoughts before I go down to the workshop and ask them to fix it at their expense?

[ross46]

Main jet fallen out of the holder on one carb, happened to me

[Columbo]

Main jet fallen out of the holder on one carb, happened to me

All jets are in place.

[ross46]

wHat size jets? Are the float seals all working as they should and floats the correct height? Would say its just carb problems, but then the 70 miles to a tank im not sure about what mods are you running? Try returning it to base settings as far as you can. Is the fuel pump shutting off? No fuel leak? They may not be connected, been caught out by two seperste problems looking like one before..

[Columbo]

wHat size jets? Are the float seals all working as they should and floats the correct height? Would say its just carb problems, but then the 70 miles to a tank im not sure about what mods are you running? Try returning it to base settings as far as you can. Is the fuel pump shutting off? No fuel leak? They may not be connected, been caught out by two seperste problems looking like one before..

Running 95 Jets
Float heights set correctly
No Leaks
Pipeworx can
Haven't investigated the fuel pump. Its meant to slow down once the bike is running, isnt it?

I'm thinking the carbs ARE balanced since it runs nicely but perhaps the mixture screws have been turned too far out?

[banner001]

float heights set correctly is no indication that the fuel level is correct (you need a length of tubing to check the level of the right hand carb, then drain it into a ~50 ml container and check the quantity of fuel, repeat for the other 3 to make sure they have the same quantity - and therefore level, of fuel), have you checked the overflows to make sure you dont have a fuel leak.

i rag mine about, am running 105 main jets, k&n air filter, 3 shims on needles to richen them and an aftermarket can, and i get ~140miles to a tank...i would be thinking fuel leak.

these bikes always have flatspots around 2-5k rpm, its the transition period from pilots to needle, you can try adjusting the pilot or checking to see if a bit of choke clears it/makes it worse.

[captain orange]

Vacuum slide diaphragms spilt/damaged? quite common?.

[Columbo]

Vacuum slide diaphragms spilt/damaged? quite common?.

Holes in the Diaphragms would stop the slides from rising. Wouldnt that mean it was using LESS fuel? In anycase, i'll be taking the carbs off and having a good look around. Gotta get christmas dinner out of the way first.

Merry Christmas all!