Hi crossleymarko,

The three screws are the High RPM adjust, the Low RPM adjust and the Idle adjust. The High RPM adjusts the top speed of the engine, lean = fast but hot running, Rich = slow but cool running. The Idle adjusts the engines idle RPM. Too slow and it will kill, too fast and the clutch will engage. The Low RPM adjustment is used to make a smooth transition from idle to high. You adjust it so when you hit the throttle the engine doesn't sputter and choke for a few seconds as it try's to transition to high RPM.

Properly adjusting a carb is a bit of an art. Experience is the key. The carburetor must be in good condition to make the engine run well. If the carburetor is dirty and in need of a rebuild you will never get it adjusted well. If you are not familiar with the procedure used to tune a carburetor you should consider taking the tool to a repair shop to have it tuned. You can quickly ruin an engine if you accidentally adjust it too lean even for a few seconds.

If the idle cannot be adjusted to that the clutch no longer engages then I would suspect a problem with the clutch itself. One of clutch pads is probably stuck.

I hope this helps you out. Good luck with your repair!

-UtahAV
-Mark

Thanks for the reply Utah, i did find that the problem was the clutch, 1 of the springs had snaped on the plate. there are 3 screws on the carb but only 2 are adjustable when the case is on. i have read that the ts400 has Intelli carb only L and LA... so would u think this carb is off another model? or is the H screw just hidden now..

thanks again..

Mark

It is probably a variation of an "EPA" carb. Every few years the EPA changes the requirements for how clean the emissions must be on gas powered equipment. Part of these changes have forced engine manufactures to adjust the carb at the factory and then cap the adjustment screws. On most current 2-cycle carburetors the Hi and Low screws are capped. Only the Idle is still adjustable. On your carb the Hi adjustment screw is likely capped so it cannot be adjusted.

-UtahAV
-Mark