# BRIGGS 18.5 HP OPPOSED TWIN I/C RUNNING ON 1 CYLINDER



## double low turtle

Hi all, l am new to the forum and need some advice where to go next in repairing the engine of one of my small tractors made by MTD around 1998. Husky model 14BS843H131 sold by Tractor Supply Co. It has sat in my basement about six years since being started. It had a bad starter and solenoid which I just replaced along with a fresh battery.









The engine is a Briggs 18.5 HP opposed twin I/C. Model #42A707 Type 2238 E1 Code 9801155A.









I have since drained the tank of old gas and added a gallon of fresh non ethanol fuel. Also changed the oil. It has the three screw fuel pump carburetor of which I cleaned and rebuilt, replacing the fuel pump springs and gaskets, carburetor gaskets and needle. All passages and jets were cleaned and flowing freely.















The seat and bowl are clean.















The float in good shape and set correctly.









The engine starts easily but will run only with choke in this position (almost closed) when at idle speed. Otherwise it will die.









When I increase the throttle fully and open the choke the engine is surging or as some say hunting. 









Everything seems to be correct on the carburetor as far as I can tell. Took fuel pump and carburetor apart multiple times to recheck and doublecheck. I hooked up a small auxiliary gas tank and line to rule out the original tank and lines and saw no difference in performance.









Continued -------------
 

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## double low turtle

Next I checked for spark on each cylinder. Both had fire. Left/right oriented from seat operators position.

Left:








Right:








Next I removed plugs. There condition as shown. 









Next reinstalled plugs, each plug is firing. Then I removed each plug wire with engine running. Upon removing the right plug wire no difference in performance, upon removal of left plug wire engine dies. Aha!

Next did compression check on each cylinder. Both checked out at around 110 psi.









So my conclusion is something is wrong with right cylinder. But what? Maybe not getting fuel/air to it. I guess I need to remove intake manifold and check for obstruction. Maybe intake valve not opening, figuring valves are not stuck open or seats loose due to compression check is good. As I said previously, it sat for a long time without turning over. Please advise what is my next steps to go from here? Any advice is appreciated.​


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## double low turtle

OK, removed intake manifold. No obstruction found there. Air flows freely.


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## Michael G Pearson

I'm guessing intake valve. Compression test only verifies valves are closed. Easy adjustment to make unless it's a push rod issue. Good hunting.


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## Michael G Pearson

Pull the valve cover off and turn the engine over to make sure the valves are moving.


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## bbirder

Hi double low,
watch this video. Shouild solve your problem.


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## double low turtle

Thanks to both of you for your replies. Once I removed the intake manifold, I could look into the port where the manifold was attached to the right cylinder. Inside I could see the intake valve stem for the right side cylinder. By turning the flywheel by hand I could observe the movement of the intake valve. Every other revolution of the flywheel the valve would open and within a half revolution close again as designed .
You can see the shiny part of the intake valve stem exposes from the guide when the valve opens 









and then recedes back into the guide when the valve closes. 









This verified all is well there as Michael suggested. bbirder, I believe you are right on figuring the coil should solve my problem. I was thinking the coil should be my next step after seeing the valve opening and closing. When I checked for spark earlier with the tester I did notice the light flashing on that cylinder was not as bright. I probably should have scrutinized it more at that point. I did not ground the plugs for spark as in the video. I got a pretty good jolt removing the wire with the engine running. My bad for assuming, forgoing the pun. I have a parts twin in my boneyard to get a spare coil from and try out when the sun rises.
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## double low turtle

Pulled the coil from my boneyard, today. Looks pretty weathered and rusty. Don't have much faith in it. Also pulled the left cylinder cover as it is missing on the Husky.







Cleaned it up best I could.







Installed cylinder cover and replaced coil. Set coil gap at .012. Fired up engine and both cylinders were working. Definitely was the coil causing the dead right cylinder. Engine was running better but still had a miss and popping ever so often like a slight backfire. Right cylinder exhaust was a good bit hotter than the left cylinder exhaust pipe. Figured left cylinder was hitting intermittently. This coil is bad too. Ordered a new coil. Should get it sometime next week. The saga continues.


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## Longhorn294

Michael G Pearson said:


> Pull the valve cover off and turn the engine over to make sure the valves are moving.[/QUOT only OHV engines have valve covers. Opposed twin is a L head engine


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