'99 M750 carb issue

[MotoPsycho]

I tried to search for it but I'm having trouble finding what I need. So I'll ask the experts.

The whole time I lived in Indiana, my bike ran like a champ. I moved to Hawaii last summer and it runs fine but won't idle to save its life. I don't know a whole lot about carbs other than a basic idea of how they work. I can tell you I adjusted the idle up a little and it helps some, but every time I go for a ride I have to leave the choke cracked a little to keep the RPM's up and it's fine. I'm idling about 1K after the last adjustment but now I'm getting a little popping just off of idle. That usually indicated a lean mixture, right ? Also if I blip it a little bit, it holds just over 1K and then drops and dies. I'm around 22K miles and have never touched the carbs. They were balanced at the 18K service a couple of years ago. First thing I plan to do when I get a chance is pull the plugs and see how they look. I know how to read plug color. I've only turned the idle adjustment screw a total of 1 1/2 turns a quarter turn at a time. I also looked up elevation where I was and it's only 60' above sea level and I'm maybe 100' above now so I'm not so sure that's it other than air quality being MUCH better here. Please help.

[ducpainter]

Are you sure you're turning the idle adjustment and not the synch screw?

It doesn't make a lot of sense, to me anyway, why your location would cause this.

[memper]

A hanging idle is usually a sign of an air intake leak.

[ChrisK]

Yeah, like Ducpainter said, you could be turning your sync screw on accident, it's really near the idle speed screw. If you need to sync your carbs up as a result of accidentally turning that and not the idle speed screw, it's very simple to build a DIY manometer and sync them up.

[MotoPsycho]

Thanks for the ideas fellas. From what I remember seeing when I had it apart a few years ago, the sync screw is up in there a little bit. The idle screw is way easier to get to from under the airbox with a regular screwdriver. I'll get my spotlight out and look up under there again to make sure I have the right one. If the sync was indeed turned by mistake, I know where to tap the intakes. I still have the hose connections. But, what vacuum range does it normally operate under? Like 10-12" mercury vac ? I worked in a distillation plant for 15 years so this makes sense to me.

[Howie]

Thanks for the ideas fellas. From what I remember seeing when I had it apart a few years ago, the sync screw is up in there a little bit. The idle screw is way easier to get to from under the airbox with a regular screwdriver. I'll get my spotlight out and look up under there again to make sure I have the right one. If the sync was indeed turned by mistake, I know where to tap the intakes. I still have the hose connections. But, what vacuum range does it normally operate under? Like 10-12" mercury vac ? I worked in a distillation plant for 15 years so this makes sense to me.

You aren't looking for a number.  You are looking for equal vacuum.  At least to me, the synch screw is easier to reach.

Try looking here for screw locations:
http://www.ducatisuite.com/carbsynch.html

I prefer mercury sticks or something like a TwinMax to a vacuum gauge.  Either you need two matche gauges or you need to go back and forth from cylinder to cylinder

[ducpainter]

One of the screws is black and the other is plated.

I wish I could remember which was which.

[MotoPsycho]

IIRC when I had it apart, the sync screw is in between? The slot in the bottom of the airbox that a screwdriver runs along to the zinc played screw is for idle I hope because that's the one I turned.

Once we move into our house I can get my manual out. It's just irritating me right now because it's not right and I can't find a logical reason for it. It being right other than it sitting for 5 or 6 weeks. No different than Indiana winters to me though.

[MotoPsycho]

The cam the throttle cables are connected to has a little arm(sort of) sticking off of it. The screw I turned touches that arm from what I can see. That should be the idle adjustment. I should just pull the pin and get some FCR's and be done with it already.

[Dellikose]

Linked from Ducatisuite:

[MotoPsycho]

Yep, that's the one. I never thought of it until now. The more I turn the screw the more it pops. I wonder if it's not leaning out but if its loading up. Is it possible I'm going the wrong way adds need to back the screw out? Looking last night, there's not much left in that spring before its compressed for the screw.

[ducpainter]

That screw only controls idle speed...not mixture.

[MotoPsycho]

Here's why I asked that. When I got the bike it already had a K&N filter on it. I don't know if it was jetted. Before I went +2 on the rear sprocket, it was acting like it was trying to flood at 55-60. That's normal highway speed. Twice it did flood. It totally fell on its face and reeked of gas in the exhaust. From what little I know about a carburetor, when it does that you hold it WOT and crank it a little at a time. I had a IH Scout that did it to me all the time. I did that on the side of the road with my bike both times and it fixed it. Added the +2 rear sprocket and it shifted the RPM's up enough it stopped. Or so it seems. The 4 or 5 track days I did the damn thing ran reallly good. But the rubber band in the motor was getting stretched pretty tight. Fast forward to now. If the RPM's are 2000ish or up everything is normal. Idle is just shit. That's what's confusing me.

[ducpainter]

How many miles on the bike?

[MotoPsycho]

I said 22k before but it's just under 21K.