Briggs and Stratton engines SUCK! STAY AWAY FROM THEM! I am a mechanic but it sounds that either someone had the wrong pulg in there or the connecting rod broke in your engine! I HATE BRIGGS engines! I work on too many that fresh out of the box something internally goes wrong and briggs blames it on the person that bought it!

According to the link below, it has a Briggs 31Q777-0305. You can download an IPL from Briggs for the various part#'s. Finding a replacement engine should also be simple. As long as the PTO dimensions match, the only other thing is that you MIGHT have to swap the flywheel & stator from your old engine. Here is a link that might be useful: Engine

Yes, 31P777. We now need to consider 2 things that could be affecting this problem. First, when the engine does its "crank a bit" act...........do you mean it acts like it wants to crank but just moves slightly and then stops turning? If you wait a minute it will repeat that? and it might finally catch on and run, sometimes? If that is what it is doing, I suggest that the engine is probably past due for its recommended annual valve adjustment. Have the valves ever been adjusted in the time you have owned the tractor? But, if the action you are seeing/hearing produces a "rapid fire clicking noise" from the starter solenoid for a few tries and then finally does nothing............I suspect that the battery is not being recharged when the tractor is operated. If recharging with a battery charger, or boosting from a good battery produces a dependable cranking, that sort of points toward a problem in the engine charging system. I see that the tractor has a manually engaged PTO system. If there was an electric PTO clutch you would also be complaining that the deck would not stay engaged, and that would be a symptom to weigh in on the non charging scenario. It is real easy to determine whether the charging output is OK. All you need to do is read the battery voltage while the engine IS NOT running and write down the voltage on paper. Battery voltage at this point should read at least 12.3 volts and might even read 13 volts if it has been charged recently. Next, start the engine and run it at full throttle. After running for a minute (and while it's still running at high RPM) check the battery voltage again and write down the voltage on paper. The voltage should read at least 13.7 volts and hopefully as high as 14.3 or so. If you do not observe at higher voltage at max RPM compared to the not running battery voltage, your charging system is defective.

Sounds to me like the valve clearance may be too close. When engine heats up, valve doesn't completely close. Walt Conner