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Just replaced both valves in a brigg 135292-1158-E1, lapped them in, adjusted intake to .006 and exhaust to .010. New head gasket properly torqued, carb and tank cleaned with new carb kit. Engine started right up but pops/backfires through exhaust. Could it be a bad valve or setting or anyone with any idea's? Thanks Bud

partially sheared flywheel key can cause backfire as well as too lean of carb setting

ILENGINE said:

partially sheared flywheel key can cause backfire as well as too lean of carb setting

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Checked key way, all good, air gap is set correct for magneto/coil, carb is a pulsa jet with just a small brass jet on the side. no other adjustment on it. Put in new fuel pump kit and cleaned carb really well but engines runs the same with the jet screwed in tight or backed way out. Could it be something in the carb that might be bad? Thanks for the quick response. Bud

Best thing to do at this time would be to perform a cylinder leakdown test to see if the valves are still leaking. could be the exhaust valve isn't sitting flat on the seat allowing it to leak.

ILENGINE said:

Best thing to do at this time would be to perform a cylinder leakdown test to see if the valves are still leaking. could be the exhaust valve isn't sitting flat on the seat allowing it to leak.

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Thanks, will give that a try. Bud

You said you replaced the valves, new or used ? You didn't regrind the seats, but lapped then in with the replacement valves? How were the valve guides. In you first post it seems like you still suspect valve problems, why? How is the camshaft, are you getting a good lift?

reynoldston said:

You said you replaced the valves, new or used ? You didn't regrind the seats, but lapped then in with the replacement valves? How were the valve guides. In you first post it seems like you still suspect valve problems, why? How is the camshaft, are you getting a good lift?

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If was fuel problems after all, changed out the carb and the engine runs great with no popping nor backfire. Thanks to all who responded as I really appreciate the help. Bud