***"What will removing the kill harness from the coils and do a test run tell me?"*** That was brought up due to the fact that the ignition system here (in vee twins) is configured as 2 separate magnetos...........joined together into a single kill wire circuit, for convenience when shutting down the engine. With magnetos, you must ground one leg of the primary coil circuit in order to "kill" the spark generation. A problem or obstacle arises when you have an engine configured with multiple cylinders and multiple magnetos. The focal point in this is that in order to kill both magnetos with a single kill wire circuit, you gotta join the kill wires from each magneto together so that both mags are killed simultaneously when a command to stop the engine is issued. This "command" might come from the ignition key switch when the machine operator turns the key switch to OFF, or.......the command may be issued by one of the safety interlock switches or relays (depending on the make of machine). The problem or obstacle when simply connecting the kill wires from each magneto together in the form of a "hard wire" splice is that connecting the kill wires together will cause serious and detrimental operating effects on BOTH magnetos when the engine is running. In theory, the kill wires can be kept separated from each other by providing a separate kill wire circuit for each magneto..........and running the pair of kill wires all the way to a specially designed key switch having 2 individual kill wire terminals (1 for each mag) which remain completely separated from each other until the key switch is turned off. Now, that in itself is a bit more complex than the single wire system that is industry standard.............but it gets worse. Because in modern OPE, there is a safety interlock system, with multiple switches wherein each switch can issue the command to kill the engine spark.............each switch would have to have double circuits for the magneto kill function, or a master relay for magneto kill having 2 separate circuits would have to be employed. All this double wire stuff and special switches in various locations could conceivably add hundreds of dollars per unit built to the OEMs cost of manufacture, and that cost would be passed on to the consumer. To overcome this obstacle, Briggs overcame the problem by connecting the kill wires together with 2 diodes, so that the separate magnetos stay separated electrically from each other during normal operation (and therefore do not interfere with each other's spark making business). In this manner, the kill wire function can be controlled by the same simple type of switches now in use. Now, for why this is something to be concerned about if you own one of these Briggs engines. Occasionally, one of the diodes can become defective. If becomes defective OPEN, there may not be any noticeable difference in how the engine runs, but when trying to stop the engine, one cylinder may continue to have spark. If this is on an engine that has a fuel solenoid, you might not even notice that you have a cylinder still getting spark, because the fuel solenoid stops main jet fuel when the key is turned off, and the pilot jet fuel is not enough to keep the "live cylinder" running against the dead cylinder load. But, if one of the diodes becomes SHORTED, or any sort of continuity in both directions develops, there will be some problems in how the 2 cylinders run. Tomplum's suggestion of isolating the magnetos from their kill wires is a way to determine if there is a problem of 1 cylinder being dead. But to separate the mags from their kill wires properly, you must disconnect each wire from the magneto itself, and that means taking off the flywheel cover. If you remove the flywheel cover, put it back on before running the engine or you will overheat it because with the cover off, there is no air flow across the cylinders. You will also have to choke the engine to a stop if running with the kill wires removed. This post was edited by mownie on Wed, Apr 9, 14 at 13:21

"using catch can, test for fuel flow to carb inlet by cranking engine. Be careful of fire." I would point out this will do no good as the engine has a fuel pump built into the carb. As mentioned way back up on this very old thread, check the vacuum impulse line from the engine block to the fuel pump. This will be the bottom line, gas line is on the side IF you took the fuel pump apart, did you find and properly replace the 2 tiny springs? I can send you a Service Manual for the engine IF you like. Address below, put in proper format and remind me the engine model number and what you want. Walt Conner wconner5 at frontier dot com

Capmbell35, Thanks for the post!! Especially the part on the valve adjustment. I own 3 Craftsman tractors and was having power issues on all of them. So far I adjusted valves on 2 of them and they now run like NEW!. MY 18.5 plowed through 5' high cow grass like it was not even there and no more bogging down. I too maintain my tractors very well and all have been VERY good machines. (FYI, the new craftsman tractors have lost their quality according to many reviews (2013)). The valve adjustment was simple (15 minutes). I would suggest adjusting the valves while engine is warm-hot. Adjusting procedures on the internet neglect to mention this. I include a link on how to adjust...... You saved me tons of money and time in trouble-shooting! Thank you again for posting and details on the fixes!!! Here is a link that might be useful: How to adjust valves on the B&S 18.5 Engine

I take it the warranty out by years? IMO that's why they put time limits cause they know most people won't put to many hours or do any maintenance on or in two years. When it won't start that's when you need to troubleshoot it. IMO first I would do would pull the plugs see if you getting fire at the plugs (pretty blue spark, no orangish and of course no spark) It you got spark spray carb. cleaner down the spark plug holes and see if it will start up on the carb. cleaner. If it fires of the carb. cleaner and dies you still have carb. issue or compression lost. I afraid you going to have to take the heads off and look in the comb chamber at the cylinder walls, valves and head gaskets. seems like your problem occurs after the engine heats up and of course that would be the ideal time to take compression when it quits also. my guess would be cracked head, or something causing it to loose compression, that;s why you need to take the compression when it dead, if you got 130 PSI or more then IMO the bottom end, valves are good but that IMO don't over rule the head gasket or cracked head. I would also take the cooling fin covers off and see if I see any sign of leakages before I go tearing it apart. there alot of engines that will fit Based on the shaft size and length Course it easier to get the same type engine (HP number not that important but hookups are. if they are the same then HP don't matter as long as it close to what you've got. Most problems with going with different brand are the muffler and starter setup and throttle cables arrangement and brackets and of course if it will fit under your hood cowl. For the price of honda you can get you another used mower. and fixing the old one if you can do it yourself would be the best choice money wise IMO.