Trouble Getting Going

[krista]

Leaving work now. Need to buy steel reserve and some bulleit rye on way home to try and answer.

[Speeddog]

Not sure why the slow jets fell out, but I'd wager that you didn't get 'em tight enough.
Perhaps you were interrupted while working on the carbs?
Don't overdo it, they're small brass parts.

As I understand it, you've got two reasonable-performing combinations:

6. 165 mains. 60 slows. 5th needle position. 1 turn out on fuel screw. 1.5 turns out on air screw.

12-A. 165 mains. 55 slows. 5th needle position. 2 turns out on fuel screw. 1.5 turns out air screw.

Those two are not so far apart.
Pick one of those, and from what you're describing, my thoughts are to make adjustments to the air screw, 1/8 turn at a time.

I can't over-emphasize it.
Be methodical, make one change at a time, write down the effects.
Try to keep the environmental part of it the same, so you may need to restrict your testing to roughly the same time of day.

I've found that the overlap of the effective zones of needle clip/air screw/fuel screw makes it a bit of a drawn-out process.

[koko64]

Wow, fell out. Never heard of that. That'll richen it up .
At least thats a red herring to ignore.
Nearly there.

[brad black]

my thoughts., ignore as desired

don't discount the impact of needle root diameter on a roll on issue.

tune the pilot jet for idle only.  everything above idle is mixture screw, air screw and needle root diameter.

try to keep the mixture screw and air screw close to as delivered / 1 turn out area.

i always use resistor plugs too

[ChrisK]

Thank you, you three, for staying tuned in!

Speeddog, point taken, be methodical.  

Brad, I don't think I'd ever choose to ignore your advice.  

So, since it seems that for proper idle with 60 slows, I have to use zero or less turns on the fuel screw, and with 55 slows I have to use two or more turns... I am going to go ahead and order 58's. Those seem like they'll be the proper middle ground I need, right?

From what I've been hearing from everyone, the pilot jets only really affect idle, correct? Unless of course they make the beast with two backsing fall out... So, while I'm waiting for those jets, is it safe for me to address the performance at cruising throttle? I know that's not perfectly methodical, but if the pilots only affect idle, I don't see why it would be a problem.

So, assuming I go with Speeddog's advice of toying with the air screws 1/8 at a time, my first inclination is to turn them out, leaning out the mixture. I say this because I believe I hear some popping at cruising speed, which would be caused by a rich mixture. Also, just spitballing, what about needle position? I know Brad said to not count out root diameter. This isn't root diameter but what if I tried the 4th needle position instead of the 5th, thus leaning out the mixture at that 1/4 to 3/4 throttle 'cruising' range?

Brad, a few posts back you suggested maybe trying an EMR or EMS needle instead of the stock EMT. Doing that would make the root diameter smaller. Does that mean richer operation?

I know I know, I'll only change one thing at a time. But what do you guys think?

[krista]

Looking at the to contemplate needles and ChrisK's description, I ended up reworking the graph to focus solely on the needle selection for the Ducati dual FCRs:



The area you're trying to affect at is the transition from the diameter to the L1/clip region. You're pulling up the needle via the clip to add gas there.

I agree with Brad, try EMS needles.

Do not even think about EMR. Needles make a big change and you do not want to ever skip steps in that table.

[ChrisK]

God. Finally got ahold of the proper compression fitting... 40 psi in one and 50 psi in the other. Aren't they supposed to be 140ish?

make the beast with two backs. Why not right?

[krista]

Ducatis never really do compression tests well. Squirt in some WD40 and hold the throttle all the way open.

[ChrisK]

That'll be a day or two now, I had to borrow the correct fitting. Of course Ducatis don't do compression tests well.

[koko64]

With all the modifications to my M900, the EMT needle was fine until I really started messing with the airbox. I had to go to the EMR after adding a litre of capacity, modifying the velocity stacks and raising the filter. Making the airbox bigger really changed everything.
Dunno what to expect with the W motor. I'd like to see what 58 slow jets and some tweaking of the SAJ screw does before changing needles.
Certainly be interesting to see.

[Howie]

Wide open throttle and four complete revolutions, warm engine. 

[koko64]

How did you go?
What compression reading you get?
Looking forward to see how many turns of the IMS you need with 58 slow fuel jets.
It's a good test of the theory.

[ChrisK]

I was busy all day yesterday and the place I borrowed the tester from is closed today so I won't be able to look at it till tomorrow.

When I originally tested I didn't hold the throttle wide open, only got about 40-50psi.

[ChrisK]

Okay that's better. Warm motor, little squirt of WD-40, throttle wide open resulted in 150 psi in one cylinder and 155 in the other.

Whew.

[ChrisK]

Should add in here that I'm still waiting on jets. I ended up not ordering until yesterday, but I went with Ca-Cycleworks this time. They were $4 cheaper than Jets-R-Us for the assortment I needed, so kudos to them.

I have 58 slows, and EMS needles on their way, as well as that 160 main that I snapped in half, just so I have a pair.