zama carb on the weedeater

[park ranger]

I have a Stihl weedeater a FS 75 and it revs up only  when the choke is closed about 1/2 way.  I sure can't see any mix screw besides the low speed (LA).  The screen on the muffler is clean. The air filter is clean too.  I looked for a capped off mix screw but couldn't find one.  Is there one?  Thanks, Eric

[KEEP CUTTING]

Sounds like you looked at the simple things first, which is good. I'd look at the fuel filter and line just to eliminate them. Then it's time for a carburetor rebuild. If you have never done one, you can go on the Zama web site and down load lots of info and diagrams to help you. Looking at their cross-reference, this is what it says you have.But I'd verify that by the # on you carb.

Zama # C1Q-S56
Stihl # 4137 120 0604

They have an exploded view of this carburetor and it shows a fully adjustable carburetor.

[Al_Smith]

Kind of the same thing came up on another web forum concerning another older Stihl weedwacker .In doing a web search of this carb in question it's been infered that it was the same type used on the FS 80 model .

My dealers list of IPL's does not show the FS 75 model but does the 80 .The carb for that model is not listed as to maker but seems to be the same as listed for that previously mention model from the other site .Know according to some knowledgable people that model in essence was a thing made for Echo .

If that in fact is the case with the subject of this thread it is indeed one odd ball contraption .The thing has a slide throttle which resembles the Amals used on British motorcycles .Cutting to the chase though while that carb seems to be no longer available the rebuild kits still are in supply .

[KevinE]

Hi PR, the LA screw is the idle screw, if you can't find H & L screws close by, the carb jets are not adjustable on it. This is easily fixed, as Stihl run carbs with adjustable jets on most other trimmers. Just get a hold of an old carb off an FS80, FS85 or similar & put a kit into it before you put it on your trimmer & Bob's your uncle!  ;)

You should be able to pick a 2nd hand carb up at most mower shops that work on them, but if not, PM me, I've got 7 or 8 old carbs sitting on a shelf in my shed waiting kits put in them. You can have 1 for the cost of postage.

Cheers,

Kevin............

[park ranger]

Thanks for the info. I got my motorcycle carb put back together today and its running great.  So tomorow I'll sit down with the zama.  thanks again

[joe_indi]

What you seem to have is a single screw carb on your FS75.
This screw does not control fuel, rather it controls the air.
The more you turn it clockwise the more you unscrew it and the leaner the mixture gets(low and mid range)
To get it to standard setting you need to turn it anti-clockwise it the stop. Then turn it twice clockwise.
At this setting if everything else is okay, the weed eater should run without any problem.
But, in case you think its running lean other than the usual filters the item to check is the metering diaphragm.
With age it tends to become a bit stiff.Once this happens the inlet needle does not activate correctly.
Its happened to my FS74.
Joe