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Rahbas

16 HP Briggs carborator adjustment

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Rahbas
I have a 16 Hp Briggs and Stratton Twin Cylinder IC engine on my Simplicity 6216 Tractor. It seems that at idle or slower speeds it runs a bit rich. Sometimes going from idle to full throttle it even emits black smoke and doesn't run too smooth for a few seconds. It runs fine at 3/4 to full throttle but I'm wondering anyone know of a diagram that tells what the different screws do on the carb. I've been able to figure out the idle speed but the other two I'm not sure on. I tried going to Briggs and Stratton's website but they don't have anything downloadable for my engine. Model number 402707. Thanks for any help

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patrician12
For the idle adjustment allow it to fully warm up,Idle it and then turn in and out the screw in the very front bottom of the carb until the point of maximum rpm is reached.There are no other fuel adjustments.They use pretty big carbs for such a small engine but shouldn't really emit black smoke.I know this sounds silly but please check the air filter and pre filter.

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Rahbas
The air filters are new. I played around with the settings. The screw at the bottom front of the carb seems to only make a differance if I screw it all the way in, at this point the engine will die. The screw at a 45 degree angle that has the visible spring doesn't seem to make any difference at all. Could it be something is very dirty inside the carburetor itself? I'm usually really good at adjusting small engines but this one is bigger than I'm used to. I don't see a bowl on this carb. Seems strange to me. I've seem to have made a difference because the tractor runs a bit worse now. It acts like it is getting too much gas and still doesn't run smooth unless it's at 3/4 to full throttle. It does run nice at full throttle. I noticed tonight that from above idle to say 3/4 throttle it doesn't seem right. It doesn't really have much of a setting in between. I took some pictures tonight of my carburetor so it may help to identify the screws. I'm rather embarrassed because it's very dirty. Thanks in advance for any help.

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BLT
The screw under the pump is the idle adjustment screw and the 45 degree is high speed screw, sorry. Warm up engine, then set both screws about 1-1/2 turns out. Start engine at idle and with idle screw and rotate slowly back and forth until you notice the engine drop off in RPM. Set your screw at the mid point. This should set your idle adjustment. And then at high idle speed do this to the high speed screw also. This should get you to corret settings.

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Rahbas
Thanks BLT, That fixed the problem. After tilling for about 1 hour though at 3/4 to full throttle it started surging. I tried readusting the carborater but it didn't help. I'm wondering if I should pick up a carb rebuild kit tommorrow and see if that helps. Sorry to be such a pain but does anyone think the surging problem could be fixed with a carb rebuild or should I look other places first?

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Rahbas
Not sure, but it looks like someone put on a new fuel filter and gas line very recently. It couldn't hurt to blow some compressed air through and replace the filter before trying the rebuild though. I'm gonna have to buy a manual for this engine but I'm trying to figure out what that rubber hose is that goes from the bottom of the engine block to the bottom of what I think may be the fuel pump. It's the line below the gas line that attaches close to the same place.

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Rahbas
Thanks very much everyone for all the help. The carborator rebuild seemed to fix the problem. It appeared that one of the springs in the fuel pump area had come loose. There was a good deal of fuel sitting in the intake manifold when I pulled off the carb. This didn't seem normal to me. It runs so much better and without all the rich smell and black smoke at throttle up. I still have some adjusting to do and thanks to lsenus, I'll be able to do that now. Thanks again

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