2001 M750

[scaudill]

My Ducati runs rich in the mid range.  The needles are not adjustable, only one groove.  Would lowering the float level 0.5, 1.0 mm help?  The needle jets look OK, round not ovaled.  I know needles and needle jets are available,  before spending $ on needles and jets is that a possible fix?
Sterling

[koko64]

I would set the float levels to 14mm, check the size of the pilot jets and replace the needle jets if they have done substantial miles. Substantial can be a low number in some circumstances.

[scaudill]

I do have the floats set at 14mm.  Took of the carb tops today and to my surprise there was a 1mm steel washer under the E clip and nylon spacer. So I removed the washer and put everything back together.  When the weather warms up I'll give it a try.
The Ducati parts book shows the nylon spacer and washer but I didn't remember them.  Anyway looking forward to the test ride.
Thanks,  Sterling

[koko64]

What size pilot jets are fitted and how many miles on the needle jets?

What rev range exactly in the mid range do you think is running rich?

[scaudill]

Exhaust are straight thru with fibre glass packing.
main jet 140
pilot jet 37.5
starter jet 70

seems rich at speeds 45- 50 mph, I don't remember rpms.  May be able to ride a few miles this weekend.  I'll get back with some more info.
Thanks sterling

[scaudill]

Oh forgot, speedo indicates little over 9000 miles,  I presume that is the needle jet miles

[koko64]

Exhaust are straight thru with fibre glass packing.
main jet 140
pilot jet 37.5
starter jet 70

seems rich at speeds 45- 50 mph, I don't remember rpms.  May be able to ride a few miles this weekend.  I'll get back with some more info.
Thanks sterling

I would fit Factory Pro needle jets as I'm suspecting them. The pilot jets are not causing the issue thats for sure. 37.5 are on the smooth/leaner/fuel economy side of good and I'm running them in my 750. CCW was selling them to remove the lumpy low speed issues. The 37.5's are not as snappy as 40's or 42's, but smooth and fuel efficient.
Do you run pods or an open airbox? The 140 mains are on the rich side of good for an open airbox. They should be fine. Note: Your fuel supply may vary your results as I'm in Australia.
Ensure that the choke cable isnt too tight on the carb bracket.
Also some mild flooding can also cause similar symptoms.

[scaudill]

I'm running a stock air box with K&N filter.  I'll check the choke cable.  Hope to take a ride the afternoon.  I should be able to see if dropping the needles 1 mm helps.
Thanks again

[koko64]

If your airbox is stock and the airbox lid snorkels are in place then your main jets are quite rich also. If your main jets are Mikuni jets (marked @140), they are what I would consider using with an open airbox on the rich side.  If they are Dynojet jets marked  YJ140, they are approximately equivalent to genuine Mikuni 130 jets.

So assuming you are running Mikuni 140 main jets (which are stock for a 900), and your needle jets are 9000 miles old, you have two over rich circuits.  Stock needle jets are a brass colour. If your needle jets are a silver/chrome looking colour they are likely to be Factory Pro nickel plated items that wear well.

For reference, Dynojet suggest their DJ 148 (Mikuni 138) main jets for an open airbox with K&N filter and open slip on pipes.

[Howie]

If your airbox is stock and the airbox lid snorkels are in place then your main jets are quite rich also. If your main jets are Mikuni jets (marked @140), they are what I would consider using with an open airbox on the rich side.  If they are Dynojet jets marked  YJ140, they are approximately equivalent to genuine Mikuni 130 jets.

So assuming you are running Mikuni 140 main jets (which are stock for a 900), and your needle jets are 9000 miles old, you have two over rich circuits.  Stock needle jets are a brass colour. If your needle jets are a silver/chrome looking colour they are likely to be Factory Pro nickel plated items that wear well.

For reference, Dynojet suggest their DJ 148 (Mikuni 138) main jets for an open airbox with K&N filter and open slip on pipes.

Great detective work

[scaudill]

Took a test ride the other day.  Bike started and ran fine until it got to operating temperature.  Popping and hard to keep running, was able to return home.  So I was thinking rich, my Ducati friend Mike (1979 Ducati SS bought new) thought lean.  Before I buy needles and needle jets, I'm going to raise the needles using Mikuni (or home made) needle shims. Weather is warming up, so I have several other projects.  So stay tuned, bad selection of words.  Anyway I'll post soon.
Sterling

[greenmonster]

Hit the kill switch when running in trouble RPM range.
Look at the plugs, they`ll indicate rich/lean.

Is it smokin when poppin? Poppin-lean, rich more like smoking-boggin.
Try a ride without lid or snorkles. Less problems-you are rich.
When it starts jerkin, can you do full throttle roll-ons?

What reasons did your friend have for thinking lean? Your reasons for rich?