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briggs 18.5 hp runs rough at higher rpm


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06-27-14, 05:40 PM   #1  
briggs 18.5 hp runs rough at higher rpm

Bought mower that was suppose to have carb problems ... Would start and idle fine but with a little more throttle it would start popping and sorta backfiring through carb so bought new carb... Same problem ... So I adjusted valves ... Still same thing .. I bought new head and installed it... Same problem.... I have adjusted carb in all ways possible and checked flywheel key ... I am stunned need help

 
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06-27-14, 10:39 PM   #2  
I'm pretty sure you're going to find out you have a wiped out camshaft. Remove the valve cover and watch the valves open and close while you rotate the engine. I'm betting at least one of them barely opens at all.


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06-28-14, 08:15 AM   #3  
Is this fixable or waste of time to fix

 
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06-28-14, 09:51 AM   #4  
I'm certain whatever is wrong is fixable. The question is how much money are you willing to spend especially if you will be giving it to a shop to do the work.

 
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06-28-14, 11:21 AM   #5  
It's fixable, and not too expensive if the mower is any good. The camshaft is about 90-100 bux. It will come with new lifters, but not a crankcase gasket. That's another 5-10 bux. So for around $100 you can fix it. You'll need to pull the engine, flip it over, remove the crankcase cover and pull out the old cam and lifters. Remove the valve cover so you can get the push rods out, put the new cam and lifters in, replace the gasket and put it back together. Then mount the engine and adjust the valves. Fill with oil and crank it up. With air tools and experience I can do this in 1 to 1.5 hours, so with hand tools and learning along the way, I would expect it to take 3 hours or so?


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06-28-14, 04:02 PM   #6  
Ok thanks got the part ordered will be here around the third ill post back thanks

 
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06-28-14, 11:33 PM   #7  
Did you check the valve operation to be sure the camshaft is wiped?


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06-29-14, 12:09 AM   #8  
Yes one of the first things I noticed was exhaust valve barely moved

 
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06-29-14, 12:22 AM   #9  
Ok, good. That's what I figured, but wanted to be sure.


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