FS56RC

[Scrubcadet10]

I don't know why... me and 2 strokes do not click. I can do 4 cycles all daaay long with no problems... give me 1 frickin 2 cycle and i can't do sheet with it.
The aformentioned weed trimmer is my personal one.... started running bad lately, after the usual yearly tune up, fresh fuel ,filter, making sure exhaust wasn't plugged ETC, i figured the carb may be tired so due to time constraints i bought a new ZAMA/STIHL carburetor from the local dealer. (cant remember PN) installed but i can't get it to run right still. new intake gaskets installed as well.
If i get it to idle good and rev up good, when i let off at full throttle it dies upon reaching idle. If i tune it to where it doesn't die when going back to idle, it will not reach full throttle... I've gone back and forth back and forth,little turns at a time... i even copied the turns of the old carb to new one... nope..... Anyone know of the "factory setting" where it *should* run....
Help.

 

[Scrubcadet10]

Found some factory settings that fish posted on here, 1.5 turns out, H, 3/4 turn out L.... did that... ran somewhat better, revved with no hesitation... idled poorly and inconsistently.

 

[Hammermechanicman]

If you put on a new OEM carb with the proper starting settings and it runs poorly i would pull the muffler and check for scoring and if P&C is good may have a leaking crank seal. When it won't rev up does it sound strained lean or rich blubbering?

 

[StarTech]

Most two carburetor are tune at idle first and then at high speed as the idle circuits also feed during high operations.

This is from the 2022 tune up guide from Stihl.

Note these are initial settings, final tuning may vary.

 

[Scrubcadet10]

P&C checks out good... will run and rev from mixed fuel sprayed into carb.... 108psi compression.
I went to the stihl dealer... talked to the parts guy.... he went in the back for a few minutes, came out with another carb, said "try this"..... I get home, new carb will not prime... verified lines installed correctly, fuel never makes it to the bulb, but it does pressurize the tank. It almost feels like the bulb builds up air pressure...
Experts?

 

[bertsmobile1]

P&C checks out good... will run and rev from mixed fuel sprayed into carb.... 108psi compression.
I went to the stihl dealer... talked to the parts guy.... he went in the back for a few minutes, came out with another carb, said "try this"..... I get home, new carb will not prime... verified lines installed correctly, fuel never makes it to the bulb, but it does pressurize the tank. It almost feels like the bulb builds up air pressure...
Experts?

The bulb does build up pressure
Pull the input line off the carb & pump the primer
Fuel should gush forth
If not the line or filter are blocked

 

[Hammermechanicman]

Is fuel filter good? Not clogged?
Pressure test the carb.
Verify carb tries to pull fuel when bulb is pumped. Remove carb and install fuel lines on inlet and purge nipples. Put line to pump side bn in a cup with fuel in it and pump bulb. Should suck fuel and spit it is out the purge line.

 

[StarTech]

Just had a similar failure here with a Walbro carb on FS74. I had to get pass the initial problems with carburetor as it needed new kit so cleaned it via USC. Welcome it primer was just sucking air and filling the tank. In this case it turn out to be a stuck main nozzle check valve. A piece of trash got stuck in it, keeping it from sealing on vacuum. Once I got it out things started working.

First check to see if the carburetor inlet is pulling a vacuum, if it is then the carburetor is fine. Otherwise try submerging the carburetor in fuel mix and prime it as this might loosen a stuck check valve. But as Bert said it can be clogged fuel inlet pickup line. Water in the fuel tend to corrode and clog the fuel filter [depending filter design].

For some reason Zama carburetors lately are giving more problems than usual. I have several primer carburetor mounted bases to fail on Stihl equipment. These cost as much as some of the carburetors when it comes to Stihl products since Stihl controls them.

Note: the initial complaint here from the customer was fuel pouring out. Well that was because the metering diaphragm had ripped. At least they didn't mess with the carburetor. Just got wait on new fuel lines with grommets.

 

[Scrubcadet10]

Is fuel filter good? Not clogged?
Pressure test the carb.
Verify carb tries to pull fuel when bulb is pumped. Remove carb and install fuel lines on inlet and purge nipples. Put line to pump side bn in a cup with fuel in it and pump bulb. Should suck fuel and spit it is out the purge line.

Filter is new OEM Stihl.
Will do.

 

[Scrubcadet10]

Submerged the carb in mix fuel, let it sit for awhile, then pumped the bulb with it submerged, it filled the primer bulb.... put it back on the whacker and it ran momentarily until the bulb was empty.
With the carb installed, when i press the primer, the fuel bubbles in the tank....
I'm stumped.....