I've had a Stihl FS45 line trimmer for a couple of years, and when it is running, it is the smoothest running weedeater I've ever used.  Problem is, its a PITA to actually get running.  No matter what I do, I cannot seem to get the thing cranked without flooding the carb and cylinder.  It doesn't matter if you use the choke or not, the bastard wants to flood out.  Lately, the only way I have been able to get the thing to run is to hold the throttle down and pull the cord until it starts. Problem is, this method requires me to pull the plug at least once to dry the cylinder out.  Now, once you get it going and warmed up, it typically runs great....if you can get the bastard cranked.  I've pulled the carb and cleaned it, which hasn't seemed to help.  Any suggestions?

Zama carbs suck but you can get a new one for $25.    Easier than rebuilding it.

Pull the screen out of the exhaust. I had a Stihl leafblower at work that did the same thing, ran like a beast when it finally started, the spark arrestor was plugged solid.  

Have you changed the plug lately, even if it looks clean they can still go bad.

It has the bulb, and it seems to be working fine.  I typically only pump it enough to fill the bulb, and then try cranking.  My other trimmer, a straight shaft Stihl 55, its considerably easier to crank.  All you have to do is hit the primer bulb a few times, switch the choke on, pull a couple of times, switch off choke, and it will fire right up.  

have you been running ethanol gas in it?

Read pages 22, 23, and 25 in the user manual.  The Stihl has a specific startup procedure to start and if you do it, it will work perfectly.  I have had several people complain about getting them to run, but once I showed them the procedure they work everytime.  My father was even given a brand new FS45 that the owner couldn't get running, I started it within a couple of pulls.  

The reason you can only get it to start with the throttle depressed is because it is supposed to start that way.

Flip stop switch to the I position
Squeeze the throttle and lock so the throttle stays wide open
Set the choke open
Prime at least 5 times(I prime until the bulb is full and give it another pump or two)
Pull cord until it starts then dies
Turn off choke and pull cord until it starts
Once it is running, squeeze throttle lever to disengage the tongue and settle to idle speed.


I have had my FS45 for over 7 years, and never winterized it or added fuel stabilizers other than what was in the oil.  The carbs were finally gummed up this spring, I cleaned the carbs and started using AmsOil Saber at 1:100 mix and she is back to running beautifully.

This, early carbs didn't have the ethanol rated sealants on the welch plugs in the carb. The metering diaphragm also gets hard and it will keep the inlet needle open causing it to flood. Look on the side of the carb, there will be an laser etched number that begins with 'S' eg. S53A, S58A etc. You can PM me with that  and I'll tell you what the current revision p/n is and you can go to your local dealer and buy a replacement. It's a simple 5 minute job to replace it and the new carb will be less than $30.



 

it killed the carb on our 4-stroke Stihl trimmer.  Lots of varnish.

non-ethanol gas=runs like a champ

I have a FS45, the carb has been ruined twice because of ethanol gas.

Have a new carburetor put on and use premixed fuel, Motomix from stihl and nothing else.

Its expensive but will last a year without destroying your carb.

My FS130R Trimmer will flood if you use the primar bulb.  But it will always start on one pull if you don't.  So, if you haven't , try running it without priming.  I do the same thing on my Stihl Chainsaw....

I don't have a choice here for non ethanol but I am running the Lucas fuel treatment for ethanol in all of my lawn equipment

Great thread.  I have the same trimmer/problems.  Learning a lot here.

I have the 55, I have to lock the throttle down to get it to start (per the manual)... Funny enough, I bought a Stihl edger and they seem to have done away with that feature.

I have found the pulling the cord slowly and few times, then giving it a yank seems to really help things get started.

My Stihl trimmer's button failed last year, I had to pull the spark plug cap to get it to stop.

Try to find you some non-eth gas, as others have said.

I just wish I could find some string that doesn't break so easy.

This is exactly how I start all of my Stihl tools.  Also make sure you use nothing but premium/hi test gas in it.  I also use fuel stabilizer in all of my stored gas.

Thanks for the suggestions, I'll give it a try tomorrow.

This.





 

This!

I have the FS130, first two years ran ethanol gas in it, always a bitch to start. Each year had to put in new spark plug in to boot.

Then I found some ethanol free gas, happens to be the closest gas station to my house even; starts on second or third pull. Last 5 years not a problem to be had, same spark plug this entire time.

The local Stihl dealer refers people to the ethanol free gas stations.