This is my main saw, Stihl 460. It's got plenty of miles, has taken a beating over the years, but has good compression, & runs good. Lately I've noticed at idle of I tip the bar forward, like stick it on the ground or a log, so the bar is sort of vertical it is stalling out. What would be causing that.
Nate does it just stall out or shutoff? Could be the kill switch wire rubbing somewhere and the weight of the saw against the AV mounts in that direction is causing a rub. Second would be a fine crack in the fuel pickup and the filter is pulling the crack open in the vertical position.
More than likely the carb needs a kit and is flooding it out by tipping it down and more fuel is going to the bottom end.
Does it happen regardless of fuel level? Does it happen immediately when the saw it tipped vertical or does it take a little while? Just wondering if you had low fuel in the tank and it started to sputter. Any slight surge in rpm when you tip the saw? If you start to have a fuel issue when tipped vertical (as Basod suggested with the fuel line crack), you might run lean for a bit). Cheers!
Sounds like it's got low pressure or it's flooding. My get is low pressure from a cracked fuel line. I would check all the lines first and the fuel filter. I have had a clogged fuel line in the past as well. I pulled the fuel filter and blew the lines out which fixed it. Try the free stuff first.... It's possible the carb is bad but unless your having other issues I wouldn't change that right away.
Those are indeed common failure items on any saw that's seen a good bit of wood. I would start by testing each of those (save the carb for last) and then pressure testing the saw. Nate, you asked for possible causes (and got a few good answers) and then said you want to be sure of the problem before spending money on parts. I know you have tools (hopefully a MityVac pressure/vac pump is in that collection) so here you go. Fuel filter can be checked with a vacuum pump, if it has a check valve in it, reverse the pump and apply a small amount of pressure (less than 5 psi) to test it. Pressure test the fuel line as well. While you have the pump out, you can test the carburetor metering needle to see if it's leaking, it should hold 5-7 psi without leaking down and should "pop" off its seat at a pressure specified in the shop manual for that saw/carb. If the saw otherwise runs well, I wouldn't look too hard at the carb for trouble until you have verified the engine is airtight. Speaking of which, time to block the exhaust port (piece of inner tube sandwiched in between the cyl and the muffler works well) and the intake port (similar method) then hook that pump up to the impulse line. Don't remove the line unless you intend to test it separately later or simply replace it. Apply about 7-8 psi of pressure, and then reverse the pump and put the engine under vacuum. It should hold for at least 30 seconds to be considered acceptable. If you have a leak and you're sure your test connections are tight, then you might have to pull the flywheel and the clutch to expose the crank seals for inspection. Common areas to check for leaks: spark plug, decomp valve, cylinder base gasket, crankshaft seals, crankcase gasket, impulse line and the intake boot. If I had to hazard a guess, I would say the fuel line is a likely culprit.
If it's over 5 years old I'd change the fuel line, filter, and impulse. Pull the carb apart and see if the screen is getting stopped up and how flexible the rubber parts are in it. The needle could be getting stuck hung open a little by trash.
To give examples of how these parts there saying affect running I will give my example. My 650 would lean out or blog when tipped forward or about half full of fuel. I suspected filter or line and so I pulled it and it was split right where it pushes onto the filter allow I.g it to suck air when half full or filled forward about 3/4 tank or lower. Had a poulan wild this g that would run all over the place I suspected the carb so I pulled out and the screen was plugged with sawdust as the filter had come disconnected in the tank.
Saw is a 2006 I believe. Has maybe 150 cords on it, nothing too crazy. It stalls, might sputter for a second or two. Pull the cord and it fires right back up. Doesn't seem to matter on fuel level. Correct no moonshine in the gas here, just in the cupboard. Yes I want to be somewhat sure. IE troubleshoot, not just parts replacement.
If you havent replaced the rubber or filter in the last few years I would put a new fuel and impulse line as well as filter as just PM. You can keep the old for spares if you breakdown and need to get going then...that is if there still good.
