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Discussion Starter · #1 ·
HI, I HAVE A 96 900 MONSTER WHICH HAS RECENTLY STARTED TO FOUL PLUGS WHEN RIDING IN TOWN OR TRAFFIC, SEEMS TO RUN OK AT SPEED THOUGH I HAVE NOTICED A LAG WHEN THROTTLE IS LET OFF AND THEN PUT BACK ON AGAIN QUICKLY. IF I CLEAN THE PLUGS EVERYTHING IS FINE AGAIN UNTIL BIKE GETS UP TO OPERATING TEMP AND THEN SAME AGAIN FOULED PLUGS, MAINLY REAR CYLINDER. BIKE HAS RECENTLY HAD NEW EMULSION TUBES AND NEEDLES BUT PROBLEM HAS PERSISTED. WHAT WOULD BE THE BEST WAY TO LEAN OFF THE MIXTURE AT LOW REVS? BACK OFF THE IDLE MIXTURE SCREWS OR ADJUST THE NEEDLES A NOTCH? ANY HELP OR SUGGESTIONS WOULD BE VERY WELCOME.
PAUL
 

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Paul,

Please take off your caps lock.

I would verify that the emulsion tubes and needles are the correct parts for the bike. If so, it could be the vent tubes to the diaphragm housings are kinked. That will stop the slide from lifting, and cause plug fouling.

If that isn't the cause you could go in to the carbs and verify correct assembly and needle adjustment.

Did you do the work yourself?
 

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Let us know what you find.
 

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Discussion Starter · #5 ·
just tried vent tubes, pulled them out of little triangular box and sucked and blew through them, you can actually hear rhe diaphrams move when you blow and you can taste petrol fumes when you suck. is there anything in the triangular box that can block?
 

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Not that I know of.
You may be making more vacuum than the engine. Are you mechanically inclined?
I would lift the tank, pull the airbox lid and filter. Start the bike and rev the motor. You should see the slides lift. If one lags it could be a restriction,kink, in the hose.
There are other possibilities. The enrichment valves(choke) could be stuck open. You could have a bad diaphragm. It is also possible the mech might have made a mistake and the needles might not have been installed properly.

It does seem odd that this appeared after some carb work.
 

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try an open airbox.. if you are curious, take off your airbox cover and use some twist ties or other retaining straps and ride the bike.. .. just make sure the airfilter is held in place.... you may get lucky here as most people have to rejet and all to run an open box... it may solve it... do you have carbon deposits on the inside rim of your exhaust pipes and are they aftermarket. it may have been set up for aftermarket and when they changed things they set it for stock.. but is it is running rich, as i assume you mean by fouling, you must have smaller more restictive cans on it.
 

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Discussion Starter · #8 ·
the bike is bog standard and i should have made it clear that this was happening before carb work, i will carry on with yor suggestions. the bike goes into ducati manchester on tuesday so one way or another it should be solved, will let you know the outcome......many thanks paul.
 
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