Carb Help!

[Mike Lenz]

Restoring my KTM 100 from a fire (ktm 175 bottom end and Sachs 100 top end). Using a 84 type 2 28mm Bing. Wont idle down right away and then does but when I then give it throttle it wants to die (too rich or lean). It seems like its starving for gas cuz it doesnt really load up when that happens, but I started off running the jetting from a 1980 125 as a base to start from, so it cant be starving, can it? needle is one notch from all the way down. Bing tuning manual says if wont idle down right away most likely have an air leak between cylinder and carb.  Will double check, but I dont think I do. I even cut a little notch in the front bottom of the slide like we use to do for bottom end response. I also tried the older "ringed" needle and matching needle jet. Nothing helps! Help!

[Mike Lenz]

It is a new 26mm spanish Bing you can buy on ebay for about $300. I opened it up to 28mm but I made sure all the idle passages were open again. hopefully not a carb issue itself!

[Mike Lenz]

Once it drops down it idles ok.  Its when you try to give it gas off idle that it tries to die and you have to do some fluttering with the throttle to get to raise up.

[wfopete]

Sounds like you may have a air leak causing a lean condition.  While the engine is running and showing the condition you speak of, spray some starting fluid or WD40 around the carb where it goes into the engine.  Don't be stingy with the fluid, really soak down these areas. Spray around the base gasket too. Listen to the engine RPMs.  By doing this, if you have a air leak in the area you introduce fuel to the leak and the fuel richens the mixture which should cause the engine to drop in RPM until the fuel source is gone. You could have a leak at the crank seals also.  A crank seal leak on the clutch side typically results in excessive smoke from the exhaust while if the leak is on the ignition side, it will suck air giving you the condition you described.