NotTaR of small Gasoline Engines and Rotary Lawn Mowers : Adjusting the carburetor on a 2 stroke e..  
 Copyright © 1994-2007, Samuel M. Goldwasser. All Rights Reserved. Reproduction of this document in whole or in part is permitted if both of the following conditions are satisfied: 1. This notice is included in its entirety at the beginning. 2. There is no charge except to cover the costs of copying. I may be contacted via the Sci.Electronics.Repair FAQ (www.repairfaq.org) Email Links Page.

    << Setting engine speed |  Index  | Instant troubleshooting c.. >>

Adjusting the carburetor on a 2 stroke engine

This is generic advice but probably a good place to start. It assumes that there are 2 adjusting screws - idle and high speed mixture.

(From: foxeye@www.compumise.com).

I would start with them both backed out from the closed position to 2 turns open, for starters. One should be idle mix and the other should be high speed. Crank the motor, get it warmed up. You may have to fiddle with the throttle and or choke until its warmed up. Then slowly turn in the low speed jet, until it starts to die, then back it out another 1/4 to 1/2 turn. Then hold the throttle wide open, and slowly turn in the high speed, until it really starts to smooth out and rev high, and start screaming, then back this out until it starts to run rough or slow down, and then turn it back in to midway between these two positions. Keep playing with the low speed needle until you get rapid immediate response from the throttle, and good idle with the idle adjustment. Then play with the high speed needle, but always back it out from the setting about 1/4 turn or so, from where it runs the smoothest. This setting of backing it out will allow more fuel when under a load, and keep your 2 cycle motor from running too lean. Put a load on it and just tweak the settings just a hair at a time. If you're in the ball park it won't take much adjustment either way to make a difference. Better on the rich side than lean side. Also make sure your oil / gas is mixed at the proper ratio. 99% of 2 cycle motors are adjusted the same, no mater what brand they are. Most will start and run with both screws open 2 turns initially. Just don't close the high speed off any more than necessary no matter how well it runs.