Backfire kills v tek 20 h.p.?


Old 01-09-08, 04:49 PM
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Join Date: Jan 2008
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Backfire kills v tek 20 h.p.?

Should read: Intek v twin 20 hp. Recently my mower backfired upon shut down. It was the first time it has done so. A few days later i went to start it and it turned over very quickly as if it had lost all compression. It did start, but would only idle with misfires occuring when i throttled up. Any ideas as to what could have happened? Its as if the valve timing slipped but gears don't slip. Thanks for any help you can give me!

Last edited by johns111; 01-09-08 at 05:35 PM.
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Old 01-09-08, 08:18 PM
Join Date: Sep 2007
Location: Cottage Grove, MN
Posts: 239
Kind of a tough one to start with here. I'd first make sure both cylinders have compression; A gauge would be ideal but you can ground the plug leads and stick a finger in the spark plug hole of each cylinder and crank the engine over. If both cylinders push your finger out then look to your ignition system for a fault. It is possible the bad backfire could be due to a faulty magneto or a bad spark plug too.
Old 01-10-08, 09:37 AM
Join Date: Nov 2007
Posts: 128
Remove the spark plugs and valve covers, look closely at the
rocker arms and pushrods while turning the flywheel by hand.
Check the rocker arm studs for looseness, and if you have
a set of feeler gauges, check your valve clearances. Look and make sure all of the valves return to the same height,
I think you problem is likely in this area.

Old 01-14-08, 06:09 PM
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Join Date: Jan 2008
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UPDATE! I pulled the valve cover off of the side that I suspected was the problem cylinder. The push rod dropped out as I pulled the cover off. The intake valve was pushed in about 1/4 inch. Grabbed a hammer and a piece of wooden dowel and tapped the valve further in. It did not spring back at all. Sprayed WD-40 on the stem and tapped it all the way in and pryed it out with a screwdriver. Repeated this until it freed up. Poured motor oil on the stem and worked it some more. Reassembled the motor and it fired right up!!!!! I mowed the lawn and it worked great the whole time. A local repair guy told me that if it sat unused for a long time the valve could jam up from lack of oil. I guess it was just bad luck on my part as the mower had sat for about 9 months without running.
Old 01-14-08, 07:51 PM
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Good news, and thanks for the update. Good call Fish!

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