Stihl FS 45 string trimmer whisperer needed!

[IndyDave]

Help! :smile:

My Stihl FS 45 string trimmer will only start when it's "cold". When I say cold, I mean when the heat from the engine is at ambient temperature. Like today, it's 84 degrees, and it will start once the trimmer is down near ambient.

Once "cold", it then demands full choke to start. For that matter, it want's the choke and nothing but the choke to keep running!

After it has started I have to leave it running at full throttle. Let up on the gas at all or fiddle with the choke position and it goes dead in a flash.

At this point I have to just put it aside and come back later.

I will be downloading the manual and looking through it but some tips, tricks, tribal knowledge and potent hexes would be appreciated. :wink:

 

[Trick1]

The only thing I can think of is a hole/ crack in your gas line or bad primer bulb, it sounds like it's getting to much air and full choke brings the fuel air mix to a start condition. Hope this helps

 

[bertsmobile1]

:welcome:

The first thing to do is pull off the muffler and have a good look at the bore , piston and ring.
IF there is scoring, particuarly on the ring then it is either a full rebuild or recycling time.
I mention this because you can run yourself ragged sorting out your fuel problems and still be left with a dud trimmer.

Obviously you have a fuel delivery problem
Unfortunately that can be anything from the fule cap to the impulse line from the crankcase or anywhere in between.
Without a vacuum / pressure tester you are really left with substitution with a known good part.
So start by clamping the shaft in a vice so you can work on it.
If you have a bicycle holder, they work well .

From here what you do will depend upon your motives.
If you just want it fixed quickly then buy a new fuel filter and lines. They will come complete with the grommet ready to fit
Buy a new impulse line, it is unique to Sthil
Buy a new carb, they are not much more expensive than buying the rebuild kit and these cube carbs are very difficult to clean & repair.

If you want to tinker then start at the fuel cap and work your way through.

I have assumed that you have checked or replaced the air filter already.

 

[enigma-2]

I would suspect a clogged jet in the carb. (Do you use gas with Ethanol?)

I would put some Sea Foam in the gas, run until hot and shut off (allow the Sea Foam time to disolve the clog).