Carb Screw to Jet Size Ratio Question

How many turns out on the carb mixture screws is equal to 1 jet size? Also does this ratio apply to the Mikuni 'I' series carbs also?

The stock setting for the low speed screws on the GP800 is Front - 2 1/4 turns out & rear 1 7/8 turns out. If I increase the pilot jet size can I turn the low speed screws in?

YES YOU CAN PUT A BIGGER JET IN AND SCREW IN YOUR ADJUSTERS AND GET THE SAME PERFORMACE. BUT YOU WON'T GAIN ANYTHING

Call Jeff at NOVI and tell him I said to call 828-687-7555. I beleive it is two turns out per 5 points on jet size. You want your low speed mixture screws to be between 3/4 and 1 turn out for optimum jet/air screw setting. Jeff will know for sure.

Chris Bullock

Before you buy.

Thanks! I know I won't gain anything in WOT performance but the boat loads up pretty quick at idle so I was hoping to correct that by going up on the pilot jet & in with the screws. Someone just told me it was 1 jet size = 1/2 turn on the screws, does that sound right?

I might be wrong, but I beleive that the people who wrote the mikuni carburator book have a different opinion than the one last stated.

Chris

Before you buy.

yes that sounds correct

Chris

Before you buy.

The stock carbs must have fine threads, instead of coarse threads to be 2¼ turns out from the factory. 2 turns out with fine threads equals about 1 turn out with coarse threads.

If it's loaded up now, why not start turning in on the low adjuster till it bottoms out to zero turns out? Then if it is still loading up, you will need to rejet, to a smaller jet. Are you sure it is the lows that are too big?? The highs being rich will make it load up too, on a full throttle grab from and idle. While on the trailer but in the water under load, lean down the lows and see if there is a change in the idle? if it get worse, go the other way and richen it. Get the best Idle quality by adjusting the lows. If it still 4-strokes from a full throttle grab, lean the highs down!!!