My Argo Response with 18HP Vanguard engine was running rough, had little power, backfired under load... I decided to check the valve clearances. At 1/4 inch past TDC the clearnaces all measured 0.012-0.018" - way too loose. I set them to about 0.005" and the engine ran a lot better (good power, no bogging on turns, smooth idle...)
Then, about 4 hours (run time) later, it started running bad again (same symptoms). So, I pulled the valve covers off again and found that there was no clearance in any of the valves. The springs were always somewhat compressed.
So, I adjusted them again. This time, before I put her back together, I pulled the starter cord a few times and then re-checked the clearances. They were too loose! I re-adjusted a couple times before I could actually spin the engine and not have the clearances change. Once I was able to do this, I put it back together and ran it, but it still runs poorly.
Tomorrow, I will recheck the clearances as well as try to pull off the black plastic cap over the carb adjustment screw (in case the cold weather is causing a lean condition that is confusing the matter).
I am wondering if I need new valve springs, or if the valves are sticking. Either way, I have never fixed either problem, so I would appreciate any suggestions.
By the way, one more oddity is that when I pulled the spark plugs, each one was half "dark gray" and half "new". These had about 4 hours on them.
Thanks in advance.