Stihl 046 ran but wont after shut off

[MonkeJoe]

I recently bought a 046 off a guy, it ran well then i tore it down to clean it up, rebuilt the carb, changed plugs hoses are okay, It never gave me a problem always started up in 4 or so pulls, Anyways i came around to adjusting the carb got it all dialed in ran it for a few minutes worked great then i shut it off and if wont start back up, Spark looks fine, just doesnt want to pop off though. Any ideas

 

[huskydave]

Did you replace the fuel filter, it could be clogged up. Did you try another plug? it could be fouled. I would start by replacing those items, it probably needs it anyway and they are cheap. If that doesn't work then check the impulse/fuel lines for cracks or pinholes. When I get a saw to work on I dump out all the fuel and replace it with fresh premix, this is one of the main problems with non runners that I see all the time. Often times the fuel has water in it or it is stale, the first thing I would do is get some good fuel in it.

 

[MonkeJoe]

Did you replace the fuel filter, it could be clogged up. Did you try another plug? it could be fouled. I would start by replacing those items, it probably needs it anyway and they are cheap. If that doesn't work then check the impulse/fuel lines for cracks or pinholes. When I get a saw to work on I dump out all the fuel and replace it with fresh premix, this is one of the main problems with non runners that I see all the time. Often times the fuel has water in it or it is stale, the first thing I would do is get some good fuel in it.,

Brand new OEM fuel filter, spark plugs brand new, the impulse lines seemed relatively new so i figured theyd be alright to run, I got lazy and ran that sef premix so maybe thats a big part of my issue, Perhaps im flooding the carb? It also doesnt feel like im getting much compression like i was last time i ran it. I tried starting it again after i wrote the post, got it to turn over for a second but that was it

 

[huskydave]

ok, that changes things, if the compression drops off a lot on any engine it won't start. Pull the muffler and look at the piston though the exhaust port and take some pictures if you can. Pull the plug and turn over the engine slowly and inspect the piston. Where did you have the carb screws set? how many turns out from all the way seated?

 

[MonkeJoe]

ok, that changes things, if the compression drops off a lot on any engine it won't start. Pull the muffler and look at the piston though the exhaust port and take some pictures if you can. Pull the plug and turn over the engine slowly and inspect the piston. Where did you have the carb screws set? how many turns out from all the way seated?

I saw the piston when i had it apart before and shrugged it off I cant even hang it by the starter rope it just drops instantly, Might end up needing a new top end, the High screw was out a ways maybe 3-4 turns and the Low was about a half turn. Pistons got a good scoring on it

 

[huskydave]

it must have leaned out somehow, this could have happened several ways. Bad crank seals, carb intake boot leak, wrong carb settings, bad fuel, improper oil mix. Your going to have to find out what happened and fix the issue before rebuilding. pour some of the fuel into a clear cup and take a good look at it, does it have dye in it? does it look cloudy? does it look like straight gas?

 

[stihltech]

vacuum and pressure test a must before tear down. No magic wand here . Diagnose problem and fix it. Or do it over.

 

[ZeroJunk]

"ran well then I tore it down"

I love it.

 

[Gord404]

Well if all you have the cylinder off I would bolt it back on a and don't need a piston in it, plug everything off and do your test, I usuall wrap a piece of copper wire around the wrist pin bearing, if its still on the rod, so I have it on hand when I rebuid- imo