bo dawg 517 #1 Posted June 11, 2022 (edited) Ok the 520 started running crappy end of last year and the work load gauge was close to 100%. Had to run choke partially on to run better. So I got it out this year and figured I clean the carb and put new spark plugs in and new gas filter. Started it up and still running like crap and work load gauge now at 100% just running. I pulled the plug one at a time to check for spark and the rear one was clean as new and good spark. The front one was soot covered and seemed like weaker spark, but did spark turning over. What is causing the soot? Also I noticed if the beather cover is on it will barely run till I pull the cover lid off spitting some gas out the top. What causes that? Edited June 11, 2022 by bo dawg Share this post Link to post Share on other sites
lynnmor 7,814 #2 Posted June 12, 2022 Check the compression, let's see if you have an engine to work with. 2 Share this post Link to post Share on other sites
JoeM 8,334 #3 Posted June 12, 2022 Sure does sound like a vacuum leak. Might try to spray, with a straw, on the intake manifold seam and see if there is any difference in the clean plug cylinder. If the manifold leaks it will draw all the fuel to the opposing cylinder.?? 2 Share this post Link to post Share on other sites
Kevin Bowley 140 #4 Posted June 14, 2022 In many cases of a pressurized crankcase, it is a valve or blowby issue. Try just barely pulling the oil dipstick out while running and the breather installed and see if it is pressurized via oil being pushed forcefully out of the dipstick tube. Check the compression in both cylinders, if the one with an oily plug has low compression, then you may have a valve seat that has come loose or a guide has slipped. It is caused by compression leaking into the crankcase overwhelming the breather and plugging the breather with oil. However, the "power percent gauge" is simply intake vacuum. Hi equals low power (throttle plate nearly closed creates high intake vacuum) use and little or low vacuum (throttle plate fully opened creates low vacuum) equals high power load percent. You should have an air filter light which compares outside atmospheric pressure to the pressure/vacuum on the inside (carburetor side) of the air cleaner. That light will come on when there is a high deferential between the atmospheric pressure on the inside of the filter is high in relation to atmospheric pressure on the outside of the filter. If you look at the bottom of the air cleaner, you will see a small vacuum hose which makes that measurement based on millibars of pressure/vacuum. Share this post Link to post Share on other sites
