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Discussion Starter #1
2001 Monster 750 Dark
Factory Pro Jet Kit
  • 15mm float bowl height
  • 42.5 pilot
  • 145 main
  • #2 clip on needle jet
  • K&N pods
  • Stock headers with carbon slip-ons
Bike starts (temps have been in the 90s past few days) but when choke is applied, makes no difference. In order to get the bike warmed up, requires holding the thottle open a bit.

After a few minutes, however, a blip will take the idle up to 3k RPMS.

Idle will NOT settle down... it stays up.

Adjusting the idle screw will get things to a lovely purr.

The latest attempt to change this had me following FactoryPro's recommendation:
  1. Turn idle down to 1000 RPMS (where the bike bucks and, in this case, repeatedly pops from the exhaust — obviously lean)
  2. Turned the fuel mixture screws out to 3.5 brings the idle up a bit (1100) but popping / light backfiring continues
  3. Applying choke just reduces the idle slightly
Was going to lift the floats to 14mm next but thought I'd hit this group up for ideas.

Suggestions, team?
 

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for that kit the standard setting is supposed to be 14mm from the center of the larger rectangular float
I know others with that kit have raised it to 15 mm to lean that setting
what is your elevation above sea level??
 

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i leave the float levels as std and check the fuel level against the indicators on the carb bodies.

i'd expect to have the idle mixture screws at least 4 turns out, but i'd check the co.

145 main is big for a 750, but shouldn't affect idle.

std 42.5 pilots, or ones with holes in them?

usually when they hold up it's because the underlying issue have caused it to pick up the ignition advance, so it's either under 1600 or over 2800. i'd wind the mixture screws out and the idle screw down.

maybe it has a vacuum leak? do the slides move and return correctly?
 

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You can turn the mixture screws out at least 5-1/2 turns and they are still affecting the mixture .
Since the enricheners aren’t making a difference you may want to check them. They should cause a change.
Watch the vacuum slides when you blip the throttle. Are they moving in unison and returning in unison ? Check the hoses and those little cans in the hose, everything clear, not kinked or collapsing, not plugged ?Stock hoses are thin and prone to kink if not routed right. This affects the slide movement. I replaced mine with fuel line and fuel filters.
 

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Discussion Starter #5
As always with this forum, THANK YOU for your patient and well-articulated thoughts.

@duc96r — For some reason, I never allowed myself to turn those fuel screws out more than 4 turns... After patiently working with the bike, I got her to a perfect idle by turning them out 5 1/2 turns. Took her for a successful test ride.

But of course, later, when I tried to start her and had the choke on, she sputtered and refused.

I knew that 5 1/2 was imbalanced.

So, went up a size for the pilot (she's at 45 now) and because her top end in the previous ride was utterly lethargic (she'd pull...but... it... took...forever... to... get... to... 8K RPMS) I switched the main to a whopping 147.5

She was very easy to set for idle, and the test ride was pretty smooth across all ranges, with the only exception being a full-throttle roll-on in 2nd gear being a tad boggy, so I think my No. 2 clip position needs to go to No. 1.
 

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That bike might be tuned to run fairly smoothly below 4000 rpm, but that is not the engines happy place. My carby will run smoothly down to 1500 rpm to putt across my yard , but you can’t grab a big handful of throttle as there is no accelerator pump on the carbs to help out.
If you feel you must ride around below 4000 rpm and grab a handful of throttle, transplant a Sportster engine into it.
 
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