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Discussion Starter #1
As I have posted in other post I have been mounting a used 8HP. Briggs on my 2550 after the old 5HP. Tecumseh gave up the ghost. Well I had several bugs to work out with the new engine but yesterday I finally got it running. I cut the whole yard and it ran great. The added power was a big plus over the old Tecumseh. When I was finished I stopped the mower, disengaged the blade, and put my hand on the key to shut it off when suddenly POW! The entire mower shook. I shut it off as I was already in the motion of doing. I looked it over and noticed that the muffler was almost blown apart. I pulled the rope and notice right away that there was no compression. The crankshaft spins freely and there is no air puffing out of the exhaust. I just walked off and left it sitting there. :banghead3
 

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CalifornianGravelynator
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OMG that sure stinks. was it at wot? when you disengaged the blades did the engine rev high?
 

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That is indeed nasty, especially since you say it performed so well just prior to it's catastrophic detonation! This occurred before you actually switched off?
 

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Discussion Starter #4
Yes it blew up right before I switched it off. It gained rpm when I disengaged the blade but it was nowhere near wot at the time I shut it off.
 

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Before declaring total disaster, I'd pull the head to see if the valves may be stuck. You had a big backfire out the exhaust, and it may have slammed the exhaust valve open to where it jammed wide open [more than usual, so it stuck on residual valve guide gum].
Can't hurt. This is the exact thing that caused the installation of solenoid operated valves on the bottom of float bowls.
tom
 

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If the switch was still on,the solenoid would still be feeding fuel that's academic anyway since there wasn't a solenoid, Sounds like the Exhaust valve hung open,and the fuel found a hot spot in the muffler,but only a tear down will tell for sure.
 

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close enuff works for me
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pull the spark plug,,,with a small flash light you can see the edges of the valves trough the plug hole , move the wire to the side so you don't get zapped ,,,roll the engine over to see if the valves are both going up and down
 
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