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Briggs & Stratton Intake Valve or Tappet problem


dkocian's Avatar
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12-31-17, 03:35 PM   #1  
Briggs & Stratton Intake Valve or Tappet problem

I have a Husky log splitter that uses a 6.75 hp Briggs & Stratton engine. Model # 126T02-0298-B1. It was running and just stopped suddenly. Thought it was bad gas so replaced it. Could not get it started. Pulled Carb and rebuilt it. Still would not start. Spark was good. Finally checked compression and "nothing". No compression at all. Pulled valve cover off the side and saw that exhaust valve was moving up and down but intake valve was not. No movement at all. Push rod did not move the valve. I pulled the head and engine looked OK. Some carbon but not much. Exhaust valve move in and out properly. Intake valve stayed closed. Never moved. Thought it was stuck, so I removed the retainer and spring and pulled the valve. Was not stuck. Moved freely and shaft is nice and clean. No pitting. Valve seat is great. Rotated engine and discovered that the push rod for intake is not moving at all. It is obviously in the closed position since the intake valve was fully closed. If it was "up", I would try and push it down. I have seen on another post where a slight tap on the push rod freed it up and a little penetrant oil got everything back into shape. Here, just the opposite. I feel pretty certain that I either have a bent push rod (or tappet valve (Sears), or whatever they call it on these small engines) or I have a broken or missing lobe on the camshaft. Before I pulled that cover, and went to all that hassle, I thought I would check for any words of wisdom from the experts.

 
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12-31-17, 03:59 PM   #2  
Something doesn't make sense here. You say the intake valve is closed... not moving... but no compression. If both valves close, you should have compression.

I'm no expert but if you are correct and both valves do close on your compression stroke (every 4th stroke), it sounds like you have multiple problems. Yes, either the lobe sheared off the intake side of the cam or the intake tappet has broken. (That explains no movement at the valve ).

But the lack of compression when both valves are closed means you have an additional problem... a broken compression ring or something. Blown head gasket?

 
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12-31-17, 04:10 PM   #3  
With the intake closed you wouldn't have any significant compression since the air couldn't enter the cylinder. It's probably the cam lobe has gotten worn and the tappet gave out.

You'll have to go lower into the engine to get to the cam and apparatus that drives the valves. That intake valve could be stuck down, but the cam/tappet is probably messed up. The latter probably happened first.

 
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12-31-17, 04:13 PM   #4  
That makes sense................

 
joecaption's Avatar
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12-31-17, 05:27 PM   #5  
Just making a guess, I went through at least 5, B & S engines in a year on a Dr lawn and leaf vac, most lasted less then 15 min. all had a plastic cam gear that broke in 1/2.


Last edited by joecaption; 12-31-17 at 05:53 PM.
 
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