Mystery engine issue i cant solve

[Scrubcadet10]

yep, spark plug gap is spec'd at .030"

https://bsintek.basco.com/BriggsDocumentDisplay/default.aspx?filename=flmvwHX-nfBhU7y

 

[Walker1940]

Hello everyone!

(Pictures attached)

I'm trying to fix my neighbors mower for him. He just got a used Ariens zero turn with a Briggs motor. Its in great shape but we cant get the motor to run right. Below is the list of new parts we've put on...

- new carb set to factory specs
- fuel pump
- fuel filter
- spark plug
- filter
- oil and filter
- air filter

The mower is near-impossible to start when cold. The choke/throttle has to be all the way OFF and it backfires through the muffler and carb constantly until it warms up all the way. It WILL NOT start with the choke/throttle up even a little bit. If we can even get it started, once it warms up it runs halfway decent but not perfect. We've fiddled with the carb adjustment screw a lot and nothing seems to make it any better, only worse. We're running out of parts to replace and ideas to fix it. Hence, the forum post. Any ideas or suggestions would be greatly appreciated!

Please let me know if you have any questions or need any additional details. Thanks in advance everyone!

Timing. Has Magneto moved?

 

[Scrubcadet10]

Timing. Has Magneto moved?

magneto shouldn't move, but it is possible for the flywheel to move from its relative position on the crank if the key is sheared.

 

[Mark99]

Might check the key for the flywheel and crankshaft,if its broken .Older machines would have points and condenser,that go bad but not so much on newer equipment.

 

[vonrick33]

Hello everyone!

(Pictures attached)

I'm trying to fix my neighbors mower for him. He just got a used Ariens zero turn with a Briggs motor. Its in great shape but we cant get the motor to run right. Below is the list of new parts we've put on...

- new carb set to factory specs
- fuel pump
- fuel filter
- spark plug
- filter
- oil and filter
- air filter

The mower is near-impossible to start when cold. The choke/throttle has to be all the way OFF and it backfires through the muffler and carb constantly until it warms up all the way. It WILL NOT start with the choke/throttle up even a little bit. If we can even get it started, once it warms up it runs halfway decent but not perfect. We've fiddled with the carb adjustment screw a lot and nothing seems to make it any better, only worse. We're running out of parts to replace and ideas to fix it. Hence, the forum post. Any ideas or suggestions would be greatly appreciated!

Please let me know if you have any questions or need any additional details. Thanks in advance everyone!

Sounds like you have a break in the spark plug wire. Won't crank if there's no spark. Replace the ignition coil.Gap the settings with a business card.

 

[VRR.DYNDNS>BIZ]

i would check your valve clearance...
View attachment 56487

I agree with his suspect issue.