my 1999 m750 has always been super sensitive to choke position

unless its recently ran & is still warm it needs choke to start

with the choke on it wants to idle at 3000>4000rpm.....

if you try to back choke lever off a hair to lower revs it falls on its face & stalls

Any ideas appreciated....Thanks
Sheldon

Difficult on the internet. How does it idle when warm?  Open air box?  Been jetted?

bike is box stock

it idles smooth at 1000rpm after a few mins of running

thanks
Sheldon

your choke piston may be damaged. 
when they are ruining the starter starts to do a little anything. 
just change the two choke pistons. 
also check your carburetor membranes.

1000 rpm warm idle is a little low.

Approximately how many miles on the bike?

+1 on setting the hot idle speed up towards 1100-1200. I've always gone on the higher side of good. If it runs ok otherwise I would check the slack in the choke cable at the carb end and I'm curious about the idle mixture setting and pilot jet sizes. I run the smooth and economical 37.5 pilot jets in my 99 750 and it's a bit cold blooded, so I run a slightly richer idle mixture setting.

If your local fuel is ethanol laced it will effectively lean your mixtures for any given jet size.

If the bike still has OEM jets it is real cold blooded.  Us bikes are particularly lean.  On a real cold day you would need a long warm up.  I don't remember the pilot jet size but that was different as well as a really lean idle.  As koko said, 1100-1200 RPM, if jetting is stock 3 turns out on the mixture screws, ideally you want to get the bike on an exhaust analyzer and shoot for 3-6%.  If that doesn't help you then want to delve into the carbs.  This way you can check everything and throw a jet kit in at the same time.  I don't remember the jetting on my old sevenfiddy, maybe koko can make some recommendations.  Might be time for needle jets anyway.

Hey Sheldon, what kind of climate in your parts and does the regular fuel have ethanol?

Using my admin powers...

Sheldon is in Canada, and his fuel is likely E-10.

 

Well I guess step one is up the idle rpm and check idle mixture. If idle screws are 3 turns out or less then try 3 1/2 - 4 turns. Test and get back to us.

Thanks Everybody....some good input

I'm just outside of Toronto so have Chicago-like weather

Where possible use non-ethanol gas

Bike only has around 15,000 miles.....have some long awaited bike trips planned this summer so want to get it sorted out

It's extremely cold blooded but as soon as you get a mile down the road it runs like a champ

My carbureted 1999 M750 feels a bit sluggish beside my kids fuel injected 2002 M620 but I'm told the 620 has bigger valves etc

 
For sure then turn up the idle speed a little and check the idle mixture adjustment. Set idle mixture adjustment at 3 1/2 - 4 turns out and aim for strongest, most even sounding and fastest idle when warm.
That 620 has injection and higher compression, but same size valves. I'm sure they improved the ports and combustion chambers by then.

Great you two can ride together .

3 1/2 to 4 it is, forgot I changed my pilot jets.