Briggs bends pushrods

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  #1  
Old 07-18-08, 05:29 PM
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Briggs bends pushrods

Hi, I'm a new forum member and hope someone can give me some expert advice. I've got a 1 year old Briggs & Stratton Intek (31P777) on a rider that only has about 150 hours on it. It bent the intake push rod a few days ago under normal operating conditions. I installed a new pushrod per the shop manual and checked valve clearances, etc. The motor ran great...for about 15 seconds. Then it bent the push rod again. What should I look at now? Sheared key?

Thanks.
 
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Old 07-18-08, 09:45 PM
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You may have a valve that is sticking or binding in the valve guide, or there may be excessive carbon build up on the piston and causing a conflict between the valve and the piston. In either case I think it might be a good idea to remove the head and check the valve that this is happening to.
 
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Old 07-19-08, 06:51 AM
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This MAY be covered by warranty unless user induced causes are present, more later. Unless you are using the engine for commercial work the warranty should be two years. Briggs have had some problems with push rods but mostly on 40000 series engines from what I see.

The normal suspects include valve clearances too loose, valve sticking or dragging in guide, overspeeding or rocker is cracked/bending/come loose. Rare but not unheard of are broken spring/retainers disengaged, seat out and hanging valve open, foreign object in combustion chamber the valve banged into, broken valve.

Another cause is old fuel. Not old enough to prevent running but old just the same. Varnishes up intake valve stems. When they cool they stick. If bent push rod is on intake valve, look for varnish build up on intake valve stem.
 
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Old 07-20-08, 11:10 AM
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Thanks

Thanks for the replys. I pulled the head off to check some of the things mentioned and discovered that one of the rocker arm studs had backed out a coupel of turns. Don't know why I didn't see it the first time I adjusted the valves but everything appeared to be ok at the time. Motor runs great now. Really appreciate the advice.
 
  #5  
Old 07-20-08, 03:54 PM
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Glad you got it figured out, thats great!
 
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