Jump to content

Log in or register to remove this advert

Can anyone help diagnose a Stihl brushcutter problem please?


Alpinejim
 Share

Recommended Posts

Hi, sorry if this post is in the wrong place, I'm new.

 

I have a Stihl FS450 brushcutter which suddenly stopped one day like it had run out of fuel.

I checked fuel and filled it but it would 't start.

Next I checked for a spark. There was one, although it looked a little weak to me, certainly not like I've seen on the car. Still, since there was a spark, I continued to suspect a fuel problem.

I changed the in-tank filter, the fuel line from tank to carb, the air filter and the spark plug. No start.

I checked the coil and lead and got continuity through to the spark plug cap - although it's hard to know exactly what's going on inside the coil but I checked it from the small metal tag at the back which has a wire connected.

 

Back to fuelling and I rebuilt the carb with new parts, no start.

I changed the complete carb, no start.

Now back to the spark, maybe it was weak. I changed the coil and set the gap to the flywheel at 12 thou, still no start.

I removed and cleaned the little valve that helps starting in case it was stuck causing low compression, all seems fine there.

 

I'm now at a loss to understand what to do next. I can only think that the spark is weak for some reason and not strong enough to ignite the fuel mix.

I suspected a short in the cable that goes to the handle on/off switch but, if that was so, there would be no spark at all.

The piston moves freely. Could there be a problem with the flywheel magnet? Could it degrade to the point that the spark becomes weak? I wouldn't have thought so.

 

Any help will be most appreciated.

Link to comment
Share on other sites

Log in or register to remove this advert

  • 5 years later...
41 minutes ago, Paddy1000111 said:

Apart from the above the main thing I haven't seen here is compression? Brush cutters go from freezing cold to flat out without the proper care all the time. Scored cylinders are pretty common.

I was thinking just the same, pop the muffler off and look at the state of the piston. If you have a compression gauge, it should read 150-170psi.

Not sure on the flywheel, it is possible the key has sheared but the first thing I check on pretty much all non running engines is firstly the compression, the spark then the fuel. If it isn't any of those, you just check the spark and fuel systems in more depth!

  • Like 3
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

  •  

  • Featured Adverts

About

Arbtalk.co.uk is a hub for the arboriculture industry in the UK.  
If you're just starting out and you need business, equipment, tech or training support you're in the right place.  If you've done it, made it, got a van load of oily t-shirts and have decided to give something back by sharing your knowledge or wisdom,  then you're welcome too.
If you would like to contribute to making this industry more effective and safe then welcome.
Just like a living tree, it'll always be a work in progress.
Please have a look around, sign up, share and contribute the best you have.

See you inside.

The Arbtalk Team

Follow us

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.