Carburettor Rebuild…

So,

I decided that it might improve the WOT(Wide Open Throttle) running by giving the ZX9R B carbs a rebuild.

As a bit of a grounding I watched this fellas videos on  You Tube.

Here’s what I found during the rebuild process.

The inlet manifold take-off pipes for the Megajolt MAP (Manifold Absolute Pressure) sensor were a bit loose – one was off completely – I pushed them all on tightly.

The float heights in the carbs were not even – they should all be 14mm, only 1 was – I reset them by bending the little tags on the float.

I increased the jet size to 1.6mm as per many recommendations. To richen the mid throttle range I raised the needles by adding a washer below each needle stop.

a few little back bits were found knocking about near the jets and needle valves – maybe plastic or hard rubber, i cleared these out.

After a clean up and rebuild – refit – I put them on the car and started it, but fuel came out of every orifice (even the venturi).

Stripping them once more drove me to replace the float needles and seats – reading through some forums I heard that the varnish in worn carbs keeps these things sealing, and that after cleaning this off – if they are worn troubles can arise.

I also replaced the float bowl rubber gaskets to ensure good sealing.

They looked glorious;

2nd Try – the carbs went back in quickly and the car started 1st time, alas though they still leaked fuel – from the overflow pipes – I remedied this by dropping the fuel pressure through the Filter King to around 2psi – at 3 psi the fuel must have been pushing the float valves open.

I found at part to  mid throttle the car is feels like it has more torque and the exhaust note is wetter – this I think is due to raising the needles.

It was still unhappy at WOT though – so maybe going for different main jets once more is the key.

I’m looking forward to balancing them and giving the car a good test in some dry weather to get an opinion.

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