Originally Posted by
m33g0
I tried to check everything u listed above and true is that the carburetor was opening too much during idle but the issue i observe was when i press brake the carb would close totally and the engine would stall and also i wasnt able to obtain even a 1.5mm gap so i took it out and analysis and realize that the idle screw would onli work to the max of 2mm ++ and i cant close it anymore further..should i replace the carburetor instead or ?
And if i want to replace the carburetor,can i change any 6.5mm .18 engine carburetor to it?
Okay, I'm not sure what you are trying to say but it sounds like the following:
At neutral, your idle was too far open causing the engine to "race" at idle.
Second, when you hit your brakes the throttle closed completely.
To fix these, start with problem 2. This is controled by the idle stop screw. The further "in" you turn it (this is screwing it in clockwise) the MORE open the idle will be. Sounds like you tighted it all the way down and yes, this is going to make the opening too large. Back off that screw until you get your desired opening.
At that point, you should now adjust your neutral position so that, at neutral, the carb is at the same position as it is at full brake. I usually adjust my neutral so that it takes a bit of trigger movement to get the carb to react. This way you know you won't have the carb "hanging open" a bit if you just go from throttle to neutral.
Once you have these set, start the engine and let it get up to temp then apply full brakes. Right now, the idles shouldn't drop if everything is adjusted as above. If the idle is still too high, turn the idle stop screw out (CCW) slightly to lower it. If the idle is too low, turn the idle stop screw in (CW) and the idle will come up. Once you have the idle where you want it, release the brake. If the idle "jumps up" when you release the brake, you need to adjust your throttle trim again to set neutral properly.
IMPORTANT NOTE: When the car is at idle, it should be able to freely roll back and forth. MANY times what novice nitro guys will do is set a high idle and to get it to stop moving they will set the car up so the brakes are applied at neutral to keep it from moving. DO NOT DO THIS. Check that the car will roll freely in neutral. Failure to do so will result in a melted glob of plastic where your clutch use to be.
Hope this helps.