Small Engines (Lawn Mowers, etc.): mower hard to crank briggs & stratton, briggs and stratton, briggs stratton

Question
QUESTION: Hi, I have a 15.5 Briggs and Stratton ride on mower and it won’t start. I have checked the carby and cleaned it just in case and its working fine. I have good spark and have taken the coil to be tested to be sure and that’s fine too. I have checked the key in the crank and it too is sitting nicely in position with no damage at all. At this point I thought it must be the compression, as I was getting no reading on the compression gauge I have from my car tunning kit. Some adjustments were needed and I was sure I had fixed the problem. Now it is very difficult to crank. The battery is struggling and I have put it on charge. Tried to jump start with the 4wd as well and it still struggled. Maybe I have set the valves at the wrong position. I followed the user manual which said 14” past TDC and the inlet was set at .004 and outlet at .006. The crank was spining freely before I set the valves. Also I have noticed some answer to similar problems suggesting the setting to valves should be done at TDC and not ¼” past TDC.

Regards,


George Semertzidis


ANSWER: Hi George
 Checking valves at TDC is a good rule of thumb. But what you are setting them at is incorrect. Here are the correct valve specs: intake .007-.009  exhaust .017-.019. Try these settings. Let me know.

---------- FOLLOW-UP ----------

QUESTION: thanks for the fast reply. i did get the mower running with the settings you sugested. However running very rough.With the choke on it revs high and low, the governor trying desperately to adjust the flow. Backfires and I see flames most of the time coming from the exhaust (muffler is of at the moment). At slow speed it is still running very lumpy, at fast speed it just stops. Took the spark plug out and its black and sooty. It tried the B&S valve specs and same thing. Tried TDC and 1/4 “ past TDC with yours and B&S valve specs but no noticeable difference in the performance. Took the carbie off and gave it another good cleaned and blow down, it seems to be working fine. Checked compression and it’s about 73 psi, not sure what it should be according to specs. What I did notice was that when I set the valves and crank it by hand, after the first revolution the valves had no gap at the point I had just set them, but spinning the crank once more and its perfect. So every second full turn of the crank the valves are not set right. I checked the drawings of the parts manual and it looks to me that there is only one “up” position on the cam. Not sure if what mine is doing is normal or if it might be the cause of my problem. Also noticed the inlet valve moves to the open position about ½ ‘ but the inlet valve only mover about ¼’ (rough estimates) also the inlet opens slightly just after it close but I think this is the compression release tab at work. Not sure what else to do any suggestions would be great. Thanks heaps. This is my model number   283H07-0197-E1

Regards,


George Semertzidis


Answer
The spark plug being black and sooty indicates a rich mixture (too much fuel) which would indicate a carb problem. Take a strand of wire and go through every jet and port in the carb as well as replacing the needle valve. Also, remove your pushrods and make sure they are not bent. One other thing. The muffler needs to be installed.