Spitting misfire

[1340fxd]

Stripped and sonic cleaned the carbs on my KZ1000 and rebuilt with kit from Z-Power. Fitted K&N pod air filters. Got air jets from zed1015 and increased main jets from 107.5 to 112.5.

She fires up and runs really well except for a spitting misfire when cold and coming off choke. This goes as the engine warms up but appears to be lurking occasionally in the background. What should I try to get rid of this please?

[zed1015]

Assuming all the valve clearances are in spec, spitting back through carbs is a sign of a weak mix or possibly an air leak on one or more of the rubber intake boots.
Try tweaking the mixture screws to richen up the pilot mix.

[1340fxd]

Thanks for that and yes, valve clearances just been done. I guess the rubber intake boots don't last forever - do they become porous?

[Pigford]

They tend to crack/split. For £40, if they're old, well worth changing.

If the spitting goes when motor up to temp, it may just be it's a tad lean as Rob says.

[000zeds]

They tend to crack/split. For £40, if they're old, well worth changing.

If the spitting goes when motor up to temp, it may just be it's a tad lean as Rob says.

http://www.z-power.co.uk/z900-z1-z1a-z1 ... t-z1-z1000

[Pigford]

They tend to crack/split. For £40, if they're old, well worth changing.

If the spitting goes when motor up to temp, it may just be it's a tad lean as Rob says.

http://www.z-power.co.uk/z900-z1-z1a-z1 ... t-z1-z1000

https://www.ebay.co.uk/itm/Kawasaki-Z90 ... Swv0tU7IGU

[marmck]

Assuming all the valve clearances are in spec, spitting back through carbs is a sign of a weak mix or possibly an air leak on one or more of the rubber intake boots.
Try tweaking the mixture screws to richen up the pilot mix.

Similar problem on me Z1 , just to clarify is to richen in or out Ta!

[zed1015]

If it's an air screw on the side then it's out to weaken.

[1340fxd]

Problem found and all very silly. I had fitted new fuel pipe obtained from Z-Power which is black and flexible (to replace the clear stuff that had turned hard as nails).

The issue was that the pipe bend became a kink when the temperature rose and the fuel pipe became even more flexible i.e. a few miles into the ride when engine heat had built up a bit. I have now used kart fuel tube which is clear and less prone to kinking - problem solved!

[zed1015]

It's always the little things that cause to most problems.