Stihl 460

[Knots]

Have a nearly new Stihl 460 Magnum with an issue.
Saw will start every time and run fine for a few seconds and then quits. Will restart every time.
Had same issue earlier and had dealer install new factory carb and tune up.
Ran fine for approximately 5 hours and then started doing the same thing.
Any thoughts about what I should try next?
Any ideas would be greatly appreciated.
Thanks,
Knots

 

[Auto Doc's]

If you are buying store bought premix fuel in the can, it is likely bad. Pour that garbage out. I dealt with a bunch of customers that bought that stuff from a location that had a bad batch.

Take the trouble to measure and mix your own fuel using non-Ethanol gas. Mix just enough that you think you will use in the next couple of months.

The next item to consider is replacing the plug with the exact number that the machine calls for. The plug is likely glazed over and trying to clean it will do very little good

 

[outdoorpowermike]

You need to have a vac/pressure test done to confirm no internal or external leaks are present with a soapy liquid to confirm there is no leaks. Sthil Commercial saws are only warrantied for 3 months. If it ran good after carb was replaced and same issue comes back you most likely have a vac leak after engine gets to operation temp. Also check compersion is 120psi or higher. Make sure vent valve and gas cap work properley. Intake rubber leaking will do just what you are saying.

 

[Auto Doc's]

Remove the muffler and have someone get it red hot with a torch if you don't have one. That will burn out the excess carbon that tends to collect in them. I have brought a lot of 2-strokes back to life doing that.

If exhaust is carbon choked the air/fuel mixture cannot get in properly to make it run.