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MTF newbee
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Discussion Starter #1
I have an LT16 with the Briggs flat twin. The left cylinder is not putting out as much as the right. The exhaust pulse on the right is much stronger than the left and the left plug gets fouled. This happens on my BMW flat twin when the carbs are not syncronized, but the Briggs has only one card. What could be causing this?
 

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Things that cause different power output: 1)valves, 2)rings, 3)ignition, 4)leaky intake and 5)possible obstructed muffler. A fouled spark plug, depending on the type of fouling, indicates either a too rich mixture or oil leaking internally and coating the spark plug causing misfire. If the fouling is more 'dry and flaky' it is generally rich mix. If it is 'greasy and wet-looking, and doesn't dry out...' it is likely oil fouling.
tom
 

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You are correct that that fuel system is probably not the problem.You can check compression,(roughly) by removing the plugs,and turning the engine with the starter,and put your finger or thumb over the hole,you should be able to feel the difference,if there is a large difference. There could also be a loss of voltage on the weak cylinder,due to coil problems,or "leakey" wires,a cheap "spark tester" can sometimes be used.
 

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MTF newbee
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Discussion Starter #5
I figured it out. I ran a compression test. One cylinder is at 90 PSI the other is at 0. I must have a stuck valve. I don't think that there is a hole in the piston. It is amazing how well this thing runs on one cylinder. I got it from my uncle and who knows how long it has been this way.
 

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I figured it out. I ran a compression test. One cylinder is at 90 PSI the other is at 0. I must have a stuck valve. I don't think that there is a hole in the piston. It is amazing how well this thing runs on one cylinder. I got it from my uncle and who knows how long it has been this way.
More likely a loose valve seat. That can be repaired IF it hasn't been run so much the block it wallowed out in which case, junk. Plugged cooling shroud often caused loose valve seat.

Walt Conner
 

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MTF newbee
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Discussion Starter #7
I would think that I would have some compression with a loose seat. I really have 0. The machine sat for more than a year before I got it.
 

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With just a loose seat, you would. What usually happens is that when the seat comes out of place, it won't go back in, and holds the offending valve (usually exhaust) wide open. This, of course, is if you're lucky. If not, you could have a broken rod with only one piston moving.
 
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