Briggs Opposed Twin 16hp - Not runnning smooth

jgbanshee · Apr 22, 2005

I have a 16Hp Briggs opposed twin motor on a late 80's Simplicity. I finally got the motor to start and now I cannot get the thing to run smooth. I have followed the manual on how to adjust the carb. i first started at 1-1/2 turns out and adjusted more lean and it runs a bit more smooth. But then I have problems of keeping the tractor running at idle with the lean adjustment. I do have the mower on and I am adjusting the carb under full load. The battery seems not to be charging either. Does that have anything to do with the running problem.

JINMA224XR · Apr 22, 2005

Hey jgbanshee,

On my single cylinder 12 hp B&S, I have 2 carb fuel/air adjustments. One screw is for the idle mixture adjustment and one is for high end mixture adjustment. In my book it says to adjust the High Speed first after getting the engine to start and warm up for 5 min. The high speed adjustment on my carb is on the bottom of the carburetor bowl. It says to open throttle fully to full speed, and and screw in/lean till engine starts to slow, then to turn out/rich till engine starts to slow, then to turn midway between the 2 for final setting.

Next set Throttle on idle, and adjust Idle Mixture screw. 1st turn idle mixture screw in/lean, till engine starts to slow, then turn idle mixture out/rich, till engine starts to slow, then turn the screw midpoint between the lean and rich points.

Before you adjust the carburetor though,, you should make sure that the air filter is new or clean and it might be a good idea to put some carburetor cleaner in the gas, such as stabil, that you can get at WalMarts for Small Engines.

Get Your Mowers Running &
Have a nice day,
Joe /forums/images/graemlins/cool.gif

jgbanshee · Apr 22, 2005

My twin has only one screw for adjustment. It has a suction fuel pump too.

JINMA224XR · Apr 23, 2005

</font><font color="blueclass=small">( My twin has only one screw for adjustment. It has a suction fuel pump too. )</font>

Hey jgbanshee,

Does your owners manual give you any help? If only one adjustment, then I am guessing that it is the Idle mixture screw. All the small engines that I have ever owned had 2 mixture screws for adjustment of the Idle Mixture and the other for full throttle. But they may be making the new engines without an ajustable mixture screw for full throttle now.

In which case , make sure that the air filter is clean, adjust the mixture screw that you have available and then put some carburetor cleaner in the fuel tank and if that doesn't do it, The suction fuel pump may need replacing, but I've not had any experience with these type fuel pumps, only what I've heard others say. I've heard others say, that the diaphram cracks when they get age on them. But there may be a way to test it though.

Have a nice day,
Joe

CCRZT50 · Apr 23, 2005

Change the diaphram on the fuel feed for the carburator and it should provide a more constant flow of gas. My old Wheel Horse did this and once this was changed, it acted as new again.

mark1 · Apr 23, 2005

First you need to check and see if both cylinders are actually producing power.(It'll run on one) the easiest way is to pull a plug wire off one at a time while it's running. I had one that seemed to run decent but didn't seem to have what a 16 HP engine should. I found one cylinder had the valve seats so worn they were just "floppin" around and no compression in that cylinder. it was on a old simplicity (80s) Briggs and Stratton

jgbanshee · Apr 23, 2005

I have replaced the fuel pump with the kit and my compression in both cylinders is approx 105 lbs.

frank_f15 · Apr 23, 2005

ARE YOU SURE IT IS A FUEL PROBLEM? mabey electical! a bad wire? or bad valves? did you replace the fuel filter?

JINMA224XR · Apr 23, 2005

Hey jgbanshee,

Does this carburetor have an adjustment to balance the intake into each cylinder intake manifold? If so that may have gotten out of adjustment.

When you pulled the plugs to check the Cylinder Pressure, what did the plugs look like on the ceramic/color? White, tan, brown, Black?

New Fuel filter if older than about 2 or 3 years, for sure, and if that is ok, then it may be time to check out the carburetor for cleaning and the float.

Are the valves making unusual loud noise? My little 12 hp B&S, is 17 years old and the valves are making a fairly noticeable clicking noise, and it doesn't have quiet as much power as it had when it was new,, but it is still cutting grass.

I wish I had something else to check,, but I'm about out of ideas. It may be something very simple though. Just overlooking it.

Good Luck &
Have a nice day,
Joe

jgbanshee · Apr 24, 2005

The air filter is clean, the gas filter is about 1 yr old, the fuel pump was replace, the valves dont make any obviously loud noises, and both cylinders are firing. No, there is not any adjustment for each seperate cylinder. Since I know that each cylinder is firing, does this mean that electrical is not the problem.