SX/SXi/SXi Pro Stalls at Idle

[Balduccimoto]

I just rebuilt the carbs, fixed a problem with the motor running away and dieseling, and fresh fuel lines. I bought this as a project. It's a 750 fairly stock with flame arrestor, 180 compression heads and dual keihin 40 carbs with 3 jets. Seems like it starves for fuel at idle but will run all day if I keep revving it up. The low screw was at 7/8 and I slowly turned it up 1/2 turn each time, it doesn't seem to help. High screw was at 1 1/8 and I slowly turned it up to 3. If I choke it, it will stay running. Maybe the pilot circuit is clogged? I had it sitting in lacquer over night to clean them.

 

[Balduccimoto]

I took out the carbs and sprayed carb cleaner through the idle circuits. I know the idle mixture screw controls fuel at idle but for whatever reason it's not helping me here. What's next?

 

[sxipro02]

just going off your screw settings it sounds like your jetting is way off. should be around 3/4-1 turn out tuned. if its out more go bigger, if their in more than 3/4 go smaller.

 

[tor*p*do]

was it re-jetted for the a/m air cleaner?
spraying carb cleaner will not help much: you need to disassemble the carbs
to completely clean them
guidance here: http://www.shopsbt.com/pdfs/keihincdk2.pdf

 

[Balduccimoto]

I just took them apart and cleaned them again to make sure i didnt miss something. If I clean these carbs anymore im gonna wash the metal away. This time I put the original flame arrestor on to see if it helps. Still same issue. It seems to me like I need larger jets but how much larger can I go? I have 135 main, 72 mid and 45 slow. 45 is for the idle circuit and the 72 is for transfer. Im thinking maybe I can swap the 72 into the 45 and see if I can get it to idle? These jets are for a 94 Super Sport XI.

 

[Balduccimoto]

Could the pop off pressure cause issues? I think im gonna take out the carbs and check out what the pressure is. should open up around 25 psi?

 

[OCD Solutions]

Wheres the idle screw set?

Sent from my Droid so spelling mistakes courtesy of Android keyboard.

 

[Balduccimoto]

I started from 7/8 and slowly backed out until almost 4. Mid range and WOT seem to be okay.

 

[JHD]

I think your only supposed to make 1/8 turn adjustments at a time. If you were going 1/2 turn each adjustment you probably passed where it needed to be.

 

[Balduccimoto]

I checked out the carb and did the pop off pressure. Pump it up until about 35 the needle starts to hiss. Pump to 40 and it releases fully then dribbles down all the way to 20 psi. Is this too high of a pressure and normal it should release all the way down to 20? I may try to lower the pop off pressure to about 30 and see. Some ppl say should be 25 some say 45 so where the hell am I supposed to be?

 

[Balduccimoto]

I just double checked it with a different guage and had pop off between 26-30 psi. I noticed one of the fulcrums were a bit bent so I bent it even with the other. Needles seem to have a good seat up to 20 psi where after that it starts to bleed some pressure. Everything seems healthy. Going to put fresh thick gasket with yellow silicone to eliminate any possibilities of an air leak at the base, leaning out the mixture. I'll report back soon.

 

[Balduccimoto]

No change. I put my neighbors identical carb from a 94 XI Super Sport and it ran fine. Going to dissect it tomarrow to see what jetting he has. His high was 2 1/2 and low 2 1/2

 

[Balduccimoto]

Discovered that when I rebuilt it I had put the anti-siphon valves in the incorrect order. It's supposed to be gasket, valve, metal plate. I had it valve, gasket, metal plate. I bought it all new from the dealer and put it in correctly. Runs perfect. Idk how I mixed that one up!