Bike Carbs - ZX6R & 1800 Pinto

[davidimurray]

I'm running an 1800 pinto, with a set of ZX6r bike carbs and Megajolt. I'm currently setting up the idle but run into a slight problem - let me start at the start -

ZX6r carbs have been respaced to suit the pinto by myself. I aslo took the opprotunity to strip and clean the carbs. Following rebuilding I set the needles one groove lower and the idle jet screw 3 turns out from their home position. I also blocked off the air corrector nozzles as this seem to be the reccomended advice.

Got the engine fired up nicely and now the cooling system is finished I've started some tuning and longer engine run times for testing.

The carbs have all been balanced using a pair of vacuum gauges. I then checked the timing and set it to be correct with the Megajolt. Finally I set the the idle to about 8-900RPM using the throttle stop screw.

Following all this I noticed the car was running very rich so I stuck a borrowed CO meter up the exhaust - to be confronted with a reading of 8%

Since then I've moved the circlips to either end of the needle grooves and screwed the idle screws in until they are all shut - with hardly any affect. When the engine is running, the diaphragms in the carbs are just 'bobbling' from their rest position and I can see fuel coming from the main jets. This is the same across all 4 carbs - even with the needles set in their lowest position (highest groove) there is still fuel coming out of the main jets. Best I've managed to get it down to is about 6.8% CO, but the engine will rev easily and quickly off load to the redline. After idle there is a big puff of smoke from the exhuast but this quickly clears once all the rubbish is blown out of the exhaust.

This seems to suggest that the idle circuit isn't doing anything and that the main circuit is doing all the work. I've checked the float height once and set them I what I though was the correct 17mm with the bowl off and also double checked using a clear tube from the dot on the carb body. Also when the ignition (pump) is on there is no sign of any fuel passing through the jets without the fuel running. The pump is a ZX6R pump to match the carbs

It seems to me that the 'bouncing' diaphragms seems to be the issue, but what do I do about this? I've checked the diaphragms and the little o-ring in the top caps and they all seem fine.

Has anyone got any advice on what to do next? All help much appreciated.

Cheers

Dave