I have a B&S Lawnmower with a 5.0 158cc engine. 6 months old. Engine began reving up and slowing down while in use last month. Now will start after priming engine but will immediately die. It will keep running if I keep pushing the primer but will die when I stop. What is the cause of this.

Never once in your story did you say the vehicle when it was in
the repair shop was actually properly diagnosed,nor was any
testing done that actually found any problems

That is & was the main problem

No one has done anything but throw parts at codes

Common sense tells you most if not all of the parts replaced
did not fail,isn't possible at all

You also keep saying the problem-what problem

Codes have nothing to do with replacing parts at all

Codes as used to test systems that set the codes,that doesn't
appear to have been done

You have to know the problem,when & under what conditions it occurs & the broken timing belt may be some how related

Also the vehicle sat for 5 months with old fuel in the tank

You need a fresh start & a new shop that knows how to test
a vehicle

Have these shops actually gone for a road test before & after
any work was done & looked at data & driven 20 miles or more?

Have you driven the vehicle with a mechanic along for the ride
until it acts up,without that, you have little chance they even care
to get involved,at least the parts installers you have been to

Charge the battery start the engine and confirm that the voltage at the battery is about 14 volts with engine running . If not it is likely the alternator is bad or the electrical connections from the alternator to the battery are defective.

A significant drain from the battery can be determined by observing the battery voltage after stopping the engine.

If it is under 12 and continues to drop trouble shoot for battery drain. If you suspect the radio pull the fuse and observe.

Replace Fuel Pump .

The KAM circuit for the PCM and the a/c is on the same circuit.
If the PCM does not have memory voltage it will loose the settings every time you turn the key off.
You might want to check the fuses in the engine compartment for a blown fuse for this circuit.
Of course it could have another problem too, such as a faulty idle air control valve.

It's listed in your owner's manual. Schedule A is normal driving conditions.
SCHEDULE "A"
7,500 miles (12 000km) or at 6 months
- Change engine oil.
- Replace engine oil filter.

15,000 miles (24 000km) or at 12 months
- Change engine oil.
- Replace engine oil filter.

22,500 miles (36 000km) or at 18 months
- Change engine oil.
- Replace engine oil filter.
- Inspect front wheel bearings.
- Inspect brake linings.

30,000 miles (48 000km) or at 24 months
- Change engine oil.
- Replace engine oil filter.
- Replace engine air cleaner filter.
- Replace spark plugs.
- Drain and refill automatic transmission fluid and filter (4.7L).

37,500 miles (60 000km) or at 30 months
- Change engine oil.
- Replace engine oil filter.
- Drain and refill automatic transmission fluid and filter (5.2L/5.9L).
- Drain and refill transfer case fluid.

45,000 miles (72 000km) or at 36 months
- Change engine oil.
- Replace engine oil filter.
- Inspect front wheel bearings.
- Inspect brake linings.
- Flush and replace engine coolant at 36 months, regardless of mileage.

52,500 miles (84 000km) or at 42 months
- Change engine oil.
- Replace engine oil filter.
- Flush and replace engine coolant if not done at 46 months.

60,000 miles (96 000km) or at 48 months
- Change engine oil.
- Replace engine oil filter.
- Replace engine air cleaner filter.
- Replace ignition cables (5.2L/5.9L).
- Inspect PCV valve, replace as necessary.
- Replace spark plugs.
- Inspect auto tension drive belt and replace as necessary (5.2L/5.9L).
- Drain and refill automatic transmission fluid (4.7L).

67,500 miles (108 000km) or at 54 months
- Change engine oil.
- Replace engine oil filter.
- Inspect front wheel bearings.
- Inspect brake linings.

75,000 miles (120 000km) or at 60 months
- Change engine oil.
- Replace engine oil filter.
- Drain and refill automatic transmission fluid and filter (5.2L/5.9L).
- Drain and refill transfer case.
- Flush and replace engine coolant if it has been 30,000miles (48 000km) or 24 months since last change.
- Inspect auto tension drive belt and replace if required.

82,500 miles (132 000km) or at 66 months
- Change engine oil.
- Replace engine oil filter.
- Flush and replace engine coolant if it has been 30,000miles (48 000km) or 24 months since last change.

90,000 miles (144 000km) or at 72 months
- Change engine oil.
- Replace engine oil filter.
- Replace engine air cleaner filter.
- Replace spark plugs.
- Inspect front wheel bearings.
- Inspect brake linings.
- Inspect auto tension drive belt and replace as necessary.
- Drain and refill automatic transmission fluid (4.7L).

97,500 miles (156 000km) or at 78 months
- Change engine oil.
- Replace engine oil filter.

105,000 miles (168 000km) or at 84 months
- Change engine oil.
- Replace engine oil filter.
- Flush and replace engine coolant if it has been 30,000 miles (48 000km) or 24 months since last change.
- Inspect auto tension drive belt and replace if required.

112,500 miles (181 000km) or at 90 months
- Change engine oil.
- Replace engine oil filter.
- Drain and refill automatic transmission fluid and filter (5.2L/5.9L).
- Inspect front wheel bearings.
- Inspect brake linings.
- Flush and replace engine coolant if it has been 30,000 miles (48 000km) or 24 months since last change.

120,000 miles (192 000km) or at 96 months
- Change engine oil.
- Replace engine oil filter.
- Replace engine air cleaner filter.
- Replace ignition cables (5.2L/5.9L).
- Inspect PCV valve, replace as necessary.
- Replace spark plugs.
- Inspect auto tension drive belt and replace as necessary.
- Drain and refill automatic transmission fluid (4.7L).

Thanks for using FixYa -a 4 THUMBS rating is appreciated for answering your FREE question.

IF IT IS A BRIGG & STRATTON ENGINE YOU CAN GO ONLINE TO BRIGGS & STRATTON.COM AND ASK THEIR TECH SECTION ABOUT THE PROBLEM. FOR 3 MONTHS OLD SOUNDS LIKE DIRT OR WATER MAY HAVE GOTTEN INTO THE TANK. WHEN YOU PRIME THE MOWER YOU ARE FORCING GAS INTO THE CARB AND ENGINE AFTER THAT THE ENGINE SHOULD PULL THE GAS IN THE ENGINE, I WOULD SAY THE CARB MITE NEED REBUILDING BUT NOT AT 3 MONTHS

The bike is 6 months old, or the chain/sprockets? Either way, sounds like you need a clutch.

could be a out sinked carb or gum from sitting gas won't last long

do u have a OBD 1 scan tool? try and find one on ebay for your car, I sold mine some time back, was $400 new got $50 for it, but I fixed allot of problems like yours because it allowed me to look at real time engine data going to and out of the engine control computer (ECM)

must connect scan tool to read fault codes...sorry