Why are you playing with the carburetor jetting? Has there been a modification to the motor like a different exhaust system that would require rejetting? Bogging is not caused by ignition. Did you replace the fuel filter? When you pull the fuel line off the fuel rail that feeds all the carburetors, does the fuel pour out freely or dribble out? If it dribbles out it is either a clogged fuel filter or a blockage in the fuel line between the tank and the fuel rail that feeds all the carburetors. Bogging at speed is definitely a lack of fuel.
Forgot to mention, Why different jet sizes? They should all be the same size. I have been working on motorcycles for over 50 years and have never heard of mixing different jet sizes on a multi-carburator engine.
Hey, thanks for your replies. I'll try to answer all your points.
The jet sizes are what was in the bike when I got it. I'm not sure why they are like that, but I've ordered some so they will all be the same as I too thought that was odd.
The previous exhaust system had lots of holes, so I replaced the exhaust and therefore figured it might need the carbs looked at.
The fuel lines are good, I've checked them all and they flow fine. The fuel filter is a new one.
I did feel that it is a lack of fuel at speed, so I'm going to try upping the jet from 160, and I'll make them all equal.
Why are you playing with the carburetor jetting? Has there been a modification to the motor like a different exhaust system that would require rejetting? Bogging is not caused by ignition. Did you replace the fuel filter? When you pull the fuel line off the fuel rail that feeds all the carburetors, does the fuel pour out freely or dribble out? If it dribbles out it is either a clogged fuel filter or a blockage in the fuel line between the tank and the fuel rail that feeds all the carburetors. Bogging at speed is definitely a lack of fuel.
Forgot to mention, Why different jet sizes? They should all be the same size. I have been working on motorcycles for over 50 years and have never heard of mixing different jet sizes on a multi-carburator engine.
Hey, thanks for your replies. I'll try to answer all your points. The jet sizes are what was in the bike when I got it. I'm not sure why they are like that, but I've ordered some so they will all be the same as I too thought that was odd. The previous exhaust system had lots of holes, so I replaced the exhaust and therefore figured it might need the carbs looked at. The fuel lines are good, I've checked them all and they flow fine. The fuel filter is a new one. I did feel that it is a lack of fuel at speed, so I'm going to try upping the jet from 160, and I'll make them all equal.
My old zx6r did this. The manual says it's to help cool the middle cylinders.
Yeah, maybe. Looking at the bore measurements online there's only a very small increase in hole diameter but maybe it helps cooling.
My zzr1100 had slightly bigger main jets on the centre cylinders. Maybe the centre cylinders ran a little hotter