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If you put a WT-603 carb on your Cobra motor scooter and now it will not start is there a way to tune the screws like remove one and then put it in after you got one tuned right?

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November 05, 2008 8:12PM

Put the old carb back. Playing with the setup you have named may well fry the engine. Lonnie ---- It can be done, but without the engine running, it is very difficult to tune these carbs. You'll have two needle adjustments to make, the idle and main (high speed). The idle screw is on the throttle side (closest to engine), the main is on the choke side (closest to the air cleaner). It won't run at all if either of these screws is removed, but a good starting point is to close these needles completely (not too tight, or you'll damage the needle seats!), then back them both out 1 and 1/4 turns. This is a very rich setting, so it should get the thing at least kicking. Once you have it running, you can turn them back in, leaning out the mixture, but not more than .5 or .75 turns, otherwise you risk a dangerously lean mix, which will blow the engine, gauranteed!