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Jon K.
Jon K., Small Engine Diagnostic Expert
Category: Small Engine
Satisfied Customers: 5818
Experience:  Gold certified Stihl tech, Service Manager for a rental/repair shop.Certified in most small engines
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Small engine I have a briggs and stratton Vanguard 9HP horizontal

Customer Question

I have a briggs and stratton Vanguard 9HP horizontal shaft go cart motor Model(NNN) NNN-NNNN01 Has electric start
Will not start but back fires very loud when choked. Have tried everything I can think of.
I got this motor not running here is what I have done so far.
Rebuilt and cleaned carb, currently I have a carb from the same model running motor on it just to rule it out.
So carb should not be issue.
Adjusted valves to specs in service manual and inspected, look to be working correctly
Replace spark plug
Removed, cleaned and inspected flywheel magnets and coil
Checked spark with Adjustable Ignition Spark Tester looks very strong and steady bright blue spark
compression checks good
Have disconnected ground wire to coil to eliminate kill switch problem
When turning over, sounds as it seems at times it might be tring to start but does not seam like im "close"
When I apply full choke or partial and move throttle I will get loud back fires
I have double and triple checked everything, Im fairly good with small motors, have the service manual but can not fiure this one out.
The only thing I could think of is something with the governor but I have inspected and checked the linkage, it seems to working correctly but not sure how to confirm.
Have tryed a bit of gas in carb, and carb cleaner seems like it might be trying a bit harder to start but most I get is a backfire. My gas tank was flushed out and new fuel before I started all this, and a oil change filled at proper level
Spark plug type and gap are correct
From what I can see, it is geting enough fuel but not burning until it builds up and back fires
Submitted: 6 years ago.
Category: Small Engine
Expert:  Jon K. replied 6 years ago.

Thank you for choosing Just Answer, my name is Jon and I will do my best to help you find the answer you need to resolve your problem.

Here are a few things that come to mind. First check the timing key. It sounds off to me. I would probably pull the head also and check the head gasket and the valve seats and valve heads. Make sure they are tight and seating correctly. At the same time you can check the push rods to make sure they are not bent.