ZXR7/9 Carbs/jets

[bigkev]

Evening all

I've fitted the ZX9R motor into my ZXR750 but I'm using the 750 carbs which are 38mm instead of 40mm it has massive midrange but when it gets up to around 8000rpm it farts and fucks about, if I roll the throttle on its not too bad. I've dtched the emissions crap and also the float bowl/vacuum restrictors and have tried various jets from 170 right down to 128 , ita seems to run best with 150's in so does anybody have a similar setup and what parts are you using.

Thanks

Kev

[fran9r]

It is a B model? I'd take a look at the B jetting, that would be a good base -I appreciate the carbs are smaller, but not massively.

Which 750 are the carbs from?

[Barry]

Have you connected all the hoses back up to the airbox from the carbs where you've ditched the emisisons stuff?

I'm running a 9B engine in a ZX7 chassis but with 39mm FCR's and a race airbox.

Are you able to post up a couple of pics, 1 with no airbox, the other with airbox and all pipes connected up?

[bigkev]

It is a B model? I'd take a look at the B jetting, that would be a good base -I appreciate the carbs are smaller, but not massively.

fran9r it is a B3 motor ,I've checked out the jets for the ZX9R and they are 200 mains ,bloody massive , but then the standard ZXR runs 190 if I remember correctly but thats with the float bowl restrictors on, so when I fitted the 9 motor I went from 160's to 170's , up 10 thinking that is an increase about the same as the standard jets however it was unridable so I wewnt back to the 750 jets and it was loads better! I'm thinking that perhaps the bigger pistons are creating a greater depression through the carb venturies and maybe drawing in more fuel than the 750?

Which 750 are the carbs from?

The carbs are the original ZXR750 ones and I have the float bowls piped up into the airbox so the pressure is equal in the carbs.