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Chris727

Briggs problem, carb or timing?

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Chris727
Hi, I have a 16hp briggs I put in my 17GTH-L last year. It developed a problem after using it only a couple of months, it will run at 1/3 throttle but any faster than that and it will sit there and cough and sputter or want to die. I tried using 3 or 4 different carbs off other good running tractors and it always does the same thing. I thought it might be a spark problem so I tried adjusting the points but this did nothing, also tried a different condensor. When I bought the engine it had a magnetron on it and ran poorly because the flywheel was not repolarized. I converted it to a kohler coil with the internal resistor. The wiring is a little goofy so I'm wondering if this is a spark problem, fuel problem, or an internal problem. Any ideas? Thanks in advance. Chris

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HubbardRA
It sounds like the main jet in the carb is partially plugged. It needs to have the varnish cleaned out of it. I have needed to clean the jet in my generator twice. I just cleaned the main jet in a relatively new push mower last week. These new fixed jet (not adjustable) carbs tend to clog up the main jet if fuel is left in the for any significant amount of time without usage.

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BLT
Also disconnect your fuel line at the carb and then with some air blow backwards into tank. I had this problem today. I used lung power and at first nothing happened and whatever was there, let loose and got blown backwards. That means later I have to take out tank and shake it up side down.

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D-17_Dave
Does pulling the choke on when it starts this problem help any? If so you are starving for fuel, clean out the fuel supply. Changing a carb off an engine jetted and adjusted for a smaller cubic inch engine will likely result in the same lean mixture condition. To properly diagnose a carb. issue you must first try adjusting the main and idle jets per the repair manual instructions. You can also be loosing compression due to a sticking valve or bad valve not seating properly. You said you swapped the cond. Did you swap out the plug with a known good one? Those are the 2 easiest things to change and they both can give you nightmares chasing odd symptoms. Slowly step through each issue and I'm sure you'll find the problem.

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Chris727
Update: Got some more time to work on it today and it is definitely not the fuel line or gas tank causing this problem. I got a perfecty clean tank (one of those light colored ones you can see inside of) and used it as a temporary tank with a short piece of fuel line (no obstructions). The engine still ran the same, only wanting to run at 1/3 throttle. I think its going to have to come out of the tractor to fix this. I also checked the compression and it has about 105 psi. I probably should take apart the carb again and re-adjust the points again, could it possiby be anything else?

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Chris727
New update. I cleaned the points, were a little oily, and put in a brand new spark plug and it started easier, and ran a little better, still can't get the carb adjusted to run more than 2/3 throttle but thats better than before. I'll try cleaning the carb and making points adjustments and hopefully that will do the trick. Thank You. Chris

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