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Just had my Stihl backpack trimmer serviced as it was running erratically and difficult to start when hot. Did 2 hours of strimming and it ran great, even idled when refilling with fuel, which it didn't do before. After a lunch break I went back to work and after about 15mins the engine just stopped dead, now it is siezed!!! So now I am wondering why it siezed after a service and running so well, any ideas? I had thought that maybe the service guy had changed the fuel mixture (in carb, not tank) so it was running lean and hence not getting enough lub, would that be the case?

Cheers

Dave

Just had a Echo backpack blower come into my shop this pass fall what the same problem happen. After I looked up the price of parts to repair the customer could buy a new blower for less money then the repairs, which I advised and he did. Unless this is a very high end Stihl you sure would want to check that out before any repairs.

The only way it will not get lube is if you didnt mix right amount of oil to the fuel.

Whats happening when you say its seized?

pugaltitude said:

The only way it will not get lube is if you didnt mix right amount of oil to the fuel.

Whats happening when you say its seized?

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The engine just stopped abruptly and it is impossible to turn the engine over, stuck solid. I have been running it on this mix for the last couple of weeks and the same mix last winter too. I would have thought that the service guy might have checked the mix ratio as a cause of the erratic running I had before?

Thanks for the replies.

Yes, it is possible to seize a 2 stroke by running very lean. More typically, it will be a clogged port in the carb causing extreme lean mixture, or possibly a needle bearing that got loose or some debris in the combustion chamber causing damage and seizure. Sometimes, piston rings will give way and wear excessively from lean running and you will get sloppy operation that can lead to seizure.

There are a few possibilities. I've just outlined some probables. Let us know what you find. I'd pop off that head and examine the Piston, rings and Chamber.

The unexplained death of a mighty Stihl is always upsetting. I would do an autopsy.

your engine just froze mid use? can you pull the starter rope easily?
This happened to me last week and it turned out a screw got loose from the cylinder and sheared off the flywheel keys and jammed the engine. All I did was clean it up, replace the flywheel and good to go.

Re: Stihl Seized!

After moving the flywheel with a screwdriver (couldn't move it with the pull start) I popped the cylinder off, marks found down the inlet side and down the exhaust side, looks very dry! I would think it has not had any oil but I know the mix does has oil in as it is red in color (2 stroke oil is red)not the usual blue color of normal petrol, so not sure what has happened. Hoping to get new piston and back running again, the cylinder was not damaged thankfully.

I spoke with the service guy and he recons he cleaned the carb and the fuel filter in the tank, then adjusted the carb, it certainly ran faster and more evenly than previously.


Thanks for the suggestions as to the fault.

One thing I forgot to say was that the fuel mixture was made up back in March, but I would have thought if anything, some petrol may have evaporated making the mixture more oily not less. I have been running my Stihl chainsaw on the same mix with no problems. Also would have thought the time that I was cutting with the trimmer was a long time if there was no oil in the mix?

Slightly off-topic -- are Stihl products that you buy in Ireland made in Germany?

I hope your trimmer is OK.

Its not something you hear of much these days seizure from lean mix.
Yes engines do run leaner to compensate emissions which then make engine running hotter but cooling systems have been adjusted to suit this.

I would say mix has not been right at one point and basically through usage it has finally worn out.

Two-Stroke said:

Slightly off-topic -- are Stihl products that you buy in Ireland made in Germany?

I hope your trimmer is OK.

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Like everybody in the world it depends on the product you want.
top end Stihl is Germany/American production but low end is coming out of China.
Europe has a problem with chromium recycling and most countrys are at their limit by certain laws.
China and other countrys dont have these laws so production is not a problem.
So mass market equipment can be made due to large volume.
the Stihl ts cut quick is usually produced in Brazil but think they are pulling out of there.

coolideas said:

One thing I forgot to say was that the fuel mixture was made up back in March, but I would have thought if anything, some petrol may have evaporated making the mixture more oily not less. I have been running my Stihl chainsaw on the same mix with no problems. Also would have thought the time that I was cutting with the trimmer was a long time if there was no oil in the mix?

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Cool:

I would never use a home brew mixture that was 8 months old.

If you can get the STIHL PRE-MIX called MOTOMIX in Ireland, I highly HIGHLY recommend it for a home user. It is premium fuel, pre-mixed with excellent 2 cycle oil, no additives or ethanol, AND it has a shelf life or tank life of TWO (2) YEARS after opening the can. It's all I use any more. Why not? I'm not a professional Arborist or someone that runs my saw every day. I probably go through 1 gallon of fuel a year, and for the money, you can't beat Stihl MotoMix. It won't gum carbs, or cause issues even when left in the tank/carb for up to 2 years after filling the tank. Worth every penny. And I bet your saw/blower/trimmer will run better with it. Mine sure does.

My 2 cents worth. :thumbsup: