The clip is mounted in the throttle slide and it's basically a kind of stopper. The 3rd setting is the needle clip setting.As you twist the throttle, the carb lets in more fuel by moving the needle in/out of the bore of the main jet, the needle lifts as you twist the throttle, this needle is adjustable and can be lifted or dropped by moving a clip up or down at the top of the needle shaft.
2 stroke tuning forum full#
All you need to do is to locate the slow idle screw and turn it fully closed (whilst at the same time counting how many full turns so that you can turn it back if you want to) and then open it 1.5 full turns and then try that.
2 stroke tuning forum manual#
I'd look to see if the slow idle screw is set correctly as per the manual - its usually around 1.5 full turns from fully closed on many scooters but check your manual to find what's right for your carb, and starting to diagnose the air/fuel mixture from this idle setting will cure many problems. One direction will make the bike run better at initial pull off so keep winding the idle screw that way until all seems right. Pause here and then do another half turn. If the engine bogs or labours for a second before it revs, then wind the idle screw in half a turn and try again, if this makes it worse wind it back and go past where it was originally. It's easy to diagnose that the idle mix is wrong when you quickly twist the throttle from idle to full. Roughly speaking if your scooter revs up and down on its own it will be weak, if the scooter ticks over unevenly and lumpy it will be too rich. When you're happy with the main jet then go onto the idle mixture setting, you need to be able to set this so that the engine idles correctly for a long period without stalling and also without the engine revs rising and dropping. A splash of petrol will likely come out but its not too much, just put some paper towels down over the engine first, and also make sure that the engine isn't red hot. You'll need to undo 2 screws to get at the carb (one fastening the carb to the inlet manifold, the other fastening it to the airfilter box though this screw may be replaced by a cable tie on some scoots), then turn it up side down and remove another 2 screws holding on the carb bowl. It is best when setting the main jet to start rich, and come down one step at a time to get it correct. The higher the number of jet, the richer it is.
2 stroke tuning forum trial#
You'll have to do this main jet swapping on a trial and error basis until the colour of the plug is correct when its inspected. Then when you've swapped the main jet try plug chopping again and assess the colour/condition again. The main jet can be found in the float bowl at the bottom of the carb. When you see the results of your plug chop then its time to swap out the main jet for one either bigger or smaller, go bigger if you want the carb to be richer, smaller if you want it to be leaner. Here's a link with more detailed instructions.
If its black or/and overly oily then its too rich, if its pale and whiteish then its too lean, you're looking for a medium brownish colour (creamy coffee colour) but if its a tad rich (slightly darker brown) then thats ok too because running too lean will risk seizing your engine. This means to run the scooter at WOT for a few blocks and then cut the engine dead, remove the spark plug and have a look at its condition. Tackle the Main Jet first - do some Plug Chops. From 3/4 to Wide Open Throttle (WOT) the main jet size is the one to look at. From 1/4 throttle to about 3/4 throttle the needle position comes into play. From idle to about 1/4 throttle you are mainly looking at adjustments to the idle mixture screw To do this well you have to understand what parts of the carb do what but the general gist of it is that 3 adjustments cover 3 parts of the rev range. On a stock 2-stroke carb there are three main ways to adjust the carb settings/mixture.
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