Hello all, I have a 2006 briggs and stratton 18.5 HP [31N707] engine that came off a craftsman. We put it on a small ariens zero turn. It worked very well for awhile, then got it where it wouldn't run unless the choke was on. Eventually it quit running all together. After this my dad parked it and it sat for 2 years.
I decided to try and fix it for him this year. There was water in the gas, so I took that tank off and drained it and dried it in the sun for a few days. I put it back on put in fresh gas. I also replaced the carb and all fuel lines and vacuum lines and filters. I put the choke on and started it and it ran for about 10 seconds, I took the choke off and now it's back to not running at all again. Tried tinkering with the air/fuel mix a bit, still no luck. If you feed it gas directly into the carb it will run. It has good spark, everything else seems to be functioning, I have no idea what else to do. I'm about to pull my hair put. Any advice on next steps would be greatly appreciated. Thank you.
Also, on these valves. The 31xxxxand 33xxxxx and most of these Briggs engines set with the Piston one quarter inch past top dead center so going down in the bore at least one quarter inch after top dead center when both valves are closed on the compression stroke, and even better if you want to go an inch or two down because it's irrelevant after that point until you get all the way to bottom dead center....and most of them sat at 004 - - .006 intake and .005 to .007 exhaust.
There are not a whole lot that set at .005 for both except your Kohler courage.
Since these numbers are also close it often works for people so then they just decide that that's the proper spec when it's actually not.
Also, since they wear loose when you pull these valve covers off you typically find them in the at least .010 to .012 range if not looser. The intake is more important than the exhaust because that's where your ACR works off of and it will be hard to crank over and act like it's bouncing back against the rubber band wall if your intake valve is too loose.
The black smoke you mentioned though is NOT indicative of the valves being out of whack. Technically, only being hard to start is indicative of the valves being out of whack. If the thing is running the valves are good enough for all intents and purposes but I would hate to see them too tight but that would only happen if someone adjusts them too tight because they don't wear tight.
Valves being tight is what burns them because they only cool when they're closed.
But other than being hard to start, if it's smoking or low on power or anything else.. it's not the valve adjustment.