Ajusting 2-stroke Carbs

[darrenc]

For those of you with 2-stroke saws, blowers, weed whackers, etc. Do you tune your own equipment (i.e., adjust your carburetor), or do you take it to a shop? For those of you who adjust your on carbs, I’m wondering what your technique is, assuming you have the standard High, Low, and Idle adjustments.

On another note, I have an inductive tachometer for my 4 stroke Honda mower. Could I use this on my 2-stroke? I’m assuming my magneto-sparked 4-stroke mower motor sparks on each 360 revolution of the crank, just like my 2-stroke. Is this a faulty assumption?

 

[SPITMAN]

set high speed mixture then set low speed mixture, adjust idle speed and repeat

 

[SPITMAN]

Warm engine to operating temperature. Set high speed mixture then set low speed mixture. Adjust idle speed. Repeat process a second time to narrow the impact of mixture change from high to low speed. BTW, this is all done with a clean carb and clean airfilter installed.

 

[blano]

The ls should be et before the hs because the ls actually effect the hs some what.

 

[Kestas]

Can you explain in more detail on how to set the high speed mixture? They say with a chain saw you're supposed to iterate between cutting and adjusting in 1/8 turn increments until you get the best operation. I have yet to develop a feel for this technique.

 

[Blue99]

Madsen's logging supplies has a detailed description of the Hi-Lo screw adjustment procedure for chainsaws.

Carburetor Adjustment Applies to any of the air cooled 2 strokes with Walbro,Zama style carbs.

Mike

fixed link for you,mark

[ October 11, 2003, 08:12 AM: Message edited by: rugerman1 ]

 

[Cujet]

On many modern 2 stroke engines with fairly lean jetting, I like to adjust the High Speed screw about 1/16 of a turn rich from maximum speed. This allows good throttle response and the ability to get the engine off choke more quickly. However the engine should not be tuned (so rich) to the point of misfire under full load. Often it is a fine line.

Chris

 

[darrenc]

Thanks again for the replies everone.

 

[eljefino]

I've found on my ratty equipment that the high speed screw is most important for curing that off-idle bog. I turn it counterclockwise until the bog just disappears. If you have to "feather" the throttle to get from idle to high speed you're way out of whack (but a common 2-stroke sickness). Prepare to readjust if you run a new batch of fuel/oil that isn't exactly like the old.

 

[eljefino]

Oh, and your magneto 4-stroke should spark every time. But it'll only do work half the time, the other half is a "waste spark".