I know Stihl has a terrible rep for starting issues especially on a hot day but I’ve found the reason (for me anyway) on the 4 mix kombi’s
If you are having the same prob which I know at least a few are by what’s written on here then you will kick yourself for how simple it is
We have two 4 mix kombi’s and never had starting issues.. nearly always first pull hot or cold, but eventually became hard to start.
Anyway after trying everything
( I even rang Stihl and spoke to a technician who thought maybe was ignition module but I knew it wasn’t as both kombi’s had issue. Dealer didn’t fix anything either)
... plug/valves/carby clean/exhaust etc.. realised it was just a blocked air filter..
But the reason why it gets blocked is the issue. It seems to be the breather from the fuel tank is vented to just behind the air filter... so if fuel travels back up the line it gets soaked reducing airflow to engine.. making hard to start (not to mention robbing power)
Seems to be two causes.. if you fill up the tank too much it can force the fuel up the line when you put the lid on .. also hot weather makes the issue worse due to heat expanding air/fuel pushing fuel up the line even more.
That explains why it is even more harder to start after a couple of jobs as the air filter gets more soaked as the day goes on.. even quicker when temps are warm. I’m guessing that usually not as bad the next morning as the fuel evaporates off.. but over time as it uses a 2 stroke mix the oil builds up in the air filter making it worse and obviously doesn’t evaporate.
The worst thing is I always cleaned the air filter but you cannot see the fuel oil inside.. so the whole time I ruled out air filter as the problem.
I realised the problem when I pulled the cord a billion times and it wouldn’t start.. pulled the air filter off .. started first pull
Anyway to fix I soaked the air filters in degreaser and they are as good as new. To stop them getting soaked I fill up before a job (so they aren’t sitting in the toolbox with the heat forcing the fuel out) and when I fill up most importantly don’t fill all the way to the top.. have to leave some air in there.
I find you still have to wash the filters but this problem is now gone. also keep a spare clean filter to swap over on the go.
I’m assuming a couple ppl on here who said they had probs with starting after filling up and also another said that fuel leaked out in the toolbox are caused by the same issue.
(note if your breather valve isn’t working this will also cause this prob)
Also another thing with the 4 mixes if you’ve had them for a while and haven’t adjusted the valves make sure you do as you will find heaps easier to pull the cord to start as it has a mechanical decompression. standard feeler gauges dont fit the Stihl so you can either get your dealer to do it for you or what i did is ordered the valve adjustment kit.. its about $10 and includes gasket / washer and special feeler gauge. i just reuse the gasket and washers and keep the new ones as spares.