Why is it?

[hughnique]

That every time you put something petrol away working it refuses to start a week later, all that pulling on that piece of rope fair on knackers me in seconds. I thought I would have a clear out of stuff I am getting too old to use so Rotovator and generator, stuck in the back of the garage come out first. My son was over last week so he provided the muscle and we eventually got both items working and advertised for sale, having put fresh petrol in and a buyer interested I thought i had better fire them up, a soaking wet sweaty tee shirt later tells me they have no intention of kicking in to life. I don't seem to have much luck with any of this petrol stuff whether it's these two items or chainsaws , strimmer's or anything else.

[Polarengineer]

I believe the biggest problem is the addition of ethyl alcohol to the petrol (E10). Which, in my machines, seems to ruin the elastomer parts. I now use expensive fuel from stihl for the two stroke items and they start easily. My honda strimmer is 4 stroke and is never a problem starting.
Ethyl alcohol is best served with ice (in the form of Vodka)

[OTBC]

The best thing to do, to start these machines "first time"....

Remove the spark plug. Put some neat petrol into the chamber ( I use a syringe....5ml will do). Put the plug back in. Press the "pump button" at least 10 times & pull the cord.

It does work!

[Doug]

OTBC,
Yes the best way, been doing that for many years.

[niemeyjt]

Modern petrol is contaminated with ethanol.

Best option is alkylated fuel like Aspen - if you have deep pockets.

Otherwise, as above.

[RobertArthur]

From the Stihl website:

If you haven’t used all the fuel in it when you come to put it away for the winter, you should make sure you do the following:

When the engine is cool, safely drain the fuel tank.
Put the fuel cap back on and attempt to start the machine. Repeat this until the engine no longer coughs.
Store the machine in a secure place away from children.

[Headers]

We now use the stihl fuel after a week of frustrating non starting machines and a bill at the repairers. That e10 stuff is awful.

[Hotrodder]

I have quite a few petrol powered tools and most of them are quite old. I use RobertArthur's method and it works 99% of the time. I am not in the position of using Stihl's off the peg special petrol given the crazy price. Later manufactured engines are supposed to be resistant to the new rubbish ethanol contaminated petrol but you don't know until you've laid down your cash if they will survive or not.

[Mangetout]

I use ordinary 98 petrol + Sthil additive and my strimmer, chainsaw and hedgecutter starts first time. I know at some point I will have to get someone to service all this stuff plus the mower but whilst it's working I leave well alone. Perhaps I'll try to learn about basic mechanics during the winter months. I wish I'd let my husband teach me when he was still alive but, like lots of things, you never think you'll find yourself needing to know.

[RobertArthur]

After one expensive Stihl fuel year I changed to 98 fuel and the special Stihl oil: 17 years later no problems.