butter fingers

[lahamm36]

I have a weedeater sst25 string trimmer, the only it will run is to have choke in middle position. I took
the ZAMA carb apart and cleaned,also tried parts from another.still no help.I tried carb. from another trimmer.
It worked. When you press prime bulb it seems to draw air from inside of carb. I don;t see a check valve
any where. Can any one help me. Thanks!

 

[lahamm36]

Ihave a weedeater sst25 string trimmer, the only it will run is to have choke in middle position. I took
the ZAMA carb apart and cleaned,also tried parts from another.still no help.I tried carb. from another trimmer.
It worked. When you press prime bulb it seems to draw air from inside of carb. I don;t see a check valve
any where. Can any one help me. Thanks!

 

[kebo]

That's telling you that the air fuel mixture isn't right. Check to see if the fuel filter is clean. Maybe the original carb needed adjustment? Also, is the air filter clean??

 

[alchemysa]

Assuming the parts are OK then it sounds like its starving for juice and you need to adjust mixture screws. The attached pdf describes carby adjustment for a typical trimmer engine with a Zama style carb.. (pages 12 - 14.)

(Incidently this pdf is for an Atom lawn edger. An Aussie design, very simple in appearance but the best edger you'll get. Much lighter and easier to use than those bulky multi wheel jobs)

 

[E/S]

That sounds a lot like a bad fuel pick-up filter in the tank. Try draining the tank and blowing back through the feed line into the tank. It will probably be really restricted.

E/S

 

[alchemysa]

I have a weedeater sst25 string trimmer, the only it will run is to have choke in middle position. I took
the ZAMA carb apart and cleaned,also tried parts from another.still no help.I tried carb. from another trimmer.
It worked. When you press prime bulb it seems to draw air from inside of carb. I don;t see a check valve
any where. Can any one help me. Thanks!

Regarding the primer. Theres a 'check' valve in the primer. And note that it doesn't pump fuel INTO the carb. It sucks it FROM the carb and returns it to the fuel tank. (The fuel enters the carby from the 'other' side). So its normal to see bubbles coming from the carb at first as you describe. Also note that the fuel hoses are different sizes. The one between the carby and primer is usually a smaller diameter than the 2 hoses in the tank. Often its a yellow color. It will suck air if you use the wrong diameter hose.

Primer bulbs don't last forever. If you doubt its quality then replace it. The primers seem to be just about 'universal' so any mower shop will have the one you need. About $10.

 

[alchemysa]

I just discovered that Zama Carbs provide an excellent free 16 page Technical Guide you can download. Covers just about everything. Its about 2.5 meg.

USA Zama : Service Tips

 

[jdfire]

For more information check out Youtube for videos on rebuilding these simple carbs. There are quite a few of them. I recently rebuilt the one on my trimmer and it works great. The parts are cheap and it's pretty easy to do, so it may be worth a try. Good luck.