# Advice on Rebuilding / Tuning 2 Cycle Carbs?



## quid_non (Nov 13, 2007)

Hi All!
I have always had good luck rebuilding carbs on 4 cycle engines - put the kit in and they seem to run well. My experience on 2 cycle (mostly Stihl = Walbro and Zama) is spotty at best. Usually, I can get them to start, but not run well or optimally. Can the " experts" share any tricks or procedures they have found?

I typically dismantle the carbs, soak briefly in a degeaser bath (sometimes w/ sonication if there is alot of gunk) then dry off and used compressed air to clean the ports out. Reassemble with new (or old) gaskets, seat all needle valves closed, then back off 1.25 turns. Is there a sequence for adjusting the H, L and idle?

Thanks for sharing your help and advice!


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## glenjudy (Aug 26, 2006)

I have pretty good luck doing this:
Disassemble, i.e., remove covers, diaphragms and gaskets.
remove L and H needles, if present, usually they are.
remove metering pin.lever, spring and needle.
put carb body in small ultrasonic cleaner with warm water and a dollop of degreaser, e.g., simple green or equivalent.
run 3 4-minute cycles.
spray with a bit of brake parts cleaner(BPC), blow dry.
spray thru L port with BPC, ensure spray exits ALL idle progression holes,
spray down thru progression holes, etc.
spray thru H port with BPC, ensure spray exits main jet.
shine fuel inlet cavity with a bit of 0000 steel wool on a broken off qtip.
spray all passages with BPC, blow dry.

I never use carb dip and have really quit using carb spray cleaner. don't put air tip against carb orifices, etc.
Reassemble, occasionally they need a new metering diaphragm if old one is stiff.
always check metering lever height, rarely use a new one.

install L and H, lightly seat and back out 1 1/2 turns to get tuning started.

To each his own, different strokes,different folks, but I've had good success with this process.
hth


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## geogrubb (Jul 28, 2006)

You can go to;
www.zamacarb.com
www.walbro.com
Select the Service/Aftermarket tab, both have great info about their carbs and how to treat them. Have a goodone. Geo


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## quid_non (Nov 13, 2007)

Perfect!
Thanks ofr the advice and links GlenJudy and GeoGrubb!:wave:
Best


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## quid_non (Nov 13, 2007)

btw...
how often do any of ya'll even mess with replacing the Welch plugs? When would I know when I need to consider it?


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## geogrubb (Jul 28, 2006)

quid_non said:


> btw...
> how often do any of ya'll even mess with replacing the Welch plugs? When would I know when I need to consider it?


I don't mess with them, any time I removed one I found it to be the cleanest part of the carb so why take the chance of damaging the housing, passage way or check valve below it. After many experiments with bath cleaner(NAPA mac 6402), ultrasonic, compressed air, carb cleaner and brake parts cleaner, I use only brake parts cleaner on the little carbs and seldom change the metering arm unless it is very worn, as it has the proper height setting. Never, never, never start poking a wire or anything in any of the tiny holes, there is usually a mylar check valve in there somewhere. The Brakes parts cleaner is tough enough and it doesn't leave a residue like other stuff. Have a good one. Geo


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