Idle Mixture DT40

[dogscoop]

Could someone tell the best way to adjust the idle mixture on a 1985 Suzuki DT40? The manual just says screw the idle mixture screw in all the way and then back it out between 1 1/4 and 1 5/8 turns. A bit vague eh?

Does turning the screw clockwise richen the mixture? I found that at some point on screwing it out the engine starts to cough (sneeze) and turning it clockwise (in) it will start to run rough and smoke a bit.

What is the best way to find the sweet spot? This is a one carb motor...


Thanks in advance

DogScoop

 

[Silvertip]

Re: Idle Mixture DT40

The setting in the manual is a rough setting. Set them at that point to start the "tweaking process". With the engine in the water (not on muffs) start the engine and warm it up. Set idle speed to spec. Then adjust one idle mixture screw inward (clockwise) in 1/16 increments, pausing for about 20 seconds each time for the engine to respond. At some point the engine will begin to sputter, cough or sneeze (use whichever term you like). Note the position of the screw slot. Then rotate the screw outward (counter clockwise) in the same manner until the engine beings to cough, sneeze, or sputter). Not that position. Somewhere in between you'll finid the best idle. At this point the engine will likely be idling a little faster so set it back down again and repeat the process on the next carb. You cannot set mixture and idle speed on muffs as there is no exhaust back pressure so they would need to be reset again when in the water. As a final adjustment, put the engine in gear and adjust the idle speed to spec.