Miss in the 870

JHH

Member
We got a miss in the 870.
About 1600 hrs. on a complete overhaul. About 100 hrs. ago she started what sounded like an exhaust valve leak that you would hear when you shut it down. Removed valve covers and found one valve with little clearance, adjusted and worked okay. Now it started missing on a cylinder when it is worked hard for a while, if you throttle it back it stops missing after a bit. Pulled valve covers again to check lash and one exhaust valve is at .010 cold. Any clues as to what is going on here?
 
Or, the spring is so relaxed that the valve is floating when revved up. I'd pull that head & investigate before you break what is left of a pounded valve or seat & do internal damage.
 
Pulled heads on the 870. Looks like there was a soft exhaust valve seat in number 3 hole, recessed obout .065.
Number 3 exhaust valve
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Number 4 exhaust valve
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Dirt will do that. 870's used 2 different Air Filters, some had the short, some had the long. Make sure you don't have a short filter stuck in a housing meant for the long element. Good luck.
 
(quoted from post at 13:51:19 11/17/12) Dirt will do that. 870's used 2 different Air Filters, some had the short, some had the long. Make sure you don't have a short filter stuck in a housing meant for the long element. Good luck.
Good observation, funny thing is if it was dirt it all went into the one hole. This 870 has a turbo and a 970 air filter.
 

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