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Ranwell1, Small Engine Technician
Category: Small Engine
Satisfied Customers: 10304
Experience:  I Own a Lawn Mower Sales and service business (37years). Have 2-cycle and 4-cycle certification.
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I have an briggs n stratton 31A607 It is blowing air back through

Customer Question

I have an briggs n stratton 31A607 It is blowing air back through the carborator instead of sucking any suggestions?
Submitted: 5 years ago.
Category: Small Engine
Expert:  cameronsmallengines replied 5 years ago.
The timing being off can cause a poor run, no run, and the backfiring. It would also cause the spark to ignite the air fuel mixture in your cylinder before the intake valve is closed which might explain your blowback through the intake.

Before we check your flywheel key for proper timing, how was your air gap on your coil set? I use a business card, or repair tag between the coil and the flywheel magnet for me air gap. Double check your air gap before proceeding further.

Lets check your flywheel key. If its sheared or partially sheared, it will cause your timing to be off. If you put a new coil on it, then you are familiar with removing the blower housing already, so I won't run through that part with you. Remove the blower housing, and then remove the nut that holds the flywheel onto the crankshaft. Now remove any washers that were between your nut and the flywheel. Your flywheel key slot in the crankshaft, and the corresponding slot in the flywheel should now be exposed. Inspect the key for a shear or partial shear and let me know what you find.
Customer: replied 5 years ago.
Im checking it
Expert:  cameronsmallengines replied 5 years ago.
I'll be looking for your reply, no rush on my end.
Customer: replied 5 years ago.

The fly wheel and the fly wheel key were in good shape the magneto was put on with the card given by b&s in the package. It still will not start

Expert:  Ranwell1 replied 5 years ago.

I really hate to butt in here but the problem is NOT the timing or the flywheel key in this instance.


The actual problem is that you have either a valve that is not closing properly or needs to be adjusted or you have a bent pushrod or a valve guide that has popped out.........




The next most likely possibility is that you have a blown head gasket. These engines blow head gaskets very regularly.


The head gasket almost always blows between the piston and the valves. This will push compression past the valve guides and into the other parts of the engine...causing some of the problems you are describing.


This engine is most likely going to have to be taken to a good shop for repair, unless you are a good enough mechanic to do the job yourself.


Here is the

Briggs & stratton Single cylinder OHV service manual

I hope this helps.


If you need any more help with this, you can contact me here at this question...even after you have hit the "ACCEPT" button to pay me for this answer.


Please click "ACCEPT" or I won't get paid.

You may also consider sending a bonus if I have been helpful, Please leave POSITIVE feedback for me as this is how I'm rated. Remember, a neutral is nearly as bad as a negative. If not satisfied, contact me and I will make it right. Thanks


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