Briggs Industrial/Commercial Opposed Twin Engines

[jpswift1]

My Hustler Big Foot has a 694cc Briggs I/C 18HP engine in it that is a "flat" or opposed twin. Do you guys have any ideas about what kind of reputation these engines have or have any tips or advice about when I get the thing running again? Thanks!

[hydromike]

Does it not run now? Fixing it up ought to be about the same as any other engine. Start with the simplest thing. Put gas and oil in it, and see what it doesn't do from the get-go. If it's been sitting for a long time, I'd throw a little oil down (across?) each cylinder and turn her over a few times by hand with the plugs out to make sure you don't start it up completely dry.

Check for a good spark, clean the points (or are the Briggs IC pointless?), you can check compression, clean the float bowl of the carb out, make sure the fuel pump is operating correctly.... I dunno. That should be a good start.

Do you have an idea of what's wrong with it now, or does it just "not run"?

~m

[liflod]

I have an 18HP opposed in my old Max IV. The biggest problem I have is with the fuel pump. I have been using an electric pump on it, but I am going to try a Mikuni pump in line with the stock pump. The engine dies after it warms up and just doesn't run that well when its warm. If I turn on the pump while its running bad, the engine immediately picks up and runs good again. There is no easy way to test the fuel pump except by pulling the top off the carb and squirting fuel into the carb to keep it running and see if there is any fuel coming out of the casting hole of the carb. Someone suggested my needle may be sticky, but I have not been able to prove or disprove that suggestion.

[jpswift1]

Mike, the guy told me that it turns over with good compression. It has been sitting in his garage for a while. I thought about taking off the heads and checking valve clearances too. I'd imagine that some fresh oil, putting some oil in the cylinders, cleaning the points, and maybe rebuilding the carb would be work just fine.
CAUTION!!!!!!! Be very careful about using electric fuel pumps! Mike, Don, and myself along with many other 6x6ers out there have seen the electric fuel pumps keep spitting fuel even when the engine backfires and starts a gas fire in your machine. I think thats a good idea to use a Mikuni fuel pump, they seem to be pretty reliable. Those engines all use the "pulse" fuel pumps that work off crank case pressure, correct? Thanks for your imput everyone.

[liflod]

The pulse pump is part of the carb. There's no easy way to by-pass it, so that's why I'm thinking about putting the Mikuni in line with it. My old Max is still in test mode, so I have an alligator clip on the fuel pump that I have been experimenting with. With the engine running with fuel dumped into the carb and the pulse line running to the Mikuni pump, I can get the pump to pump water from a coffee can.

[jpswift1]

So the carbs on those Briggs I/C engines is kind of similar to old Walboro and Tillotsons with the fuel pump right in the carb? (these things were soooooo trouble prone.) You could run an external Mikuni pump in the fuel line and it would work?

[hydromike]

Not all the Walbros were bad. My ST/440 runs a stock float-style Walbro (Scorpion sled engine) with the pump on top, and I dare say it'll give a Superchief a run for its money if it's not in tip-top shape.

Lance, from the sounds of your flat Briggs, you're running a comparable carburetor that my Case 446 runs (Onan 16-horse GA-016B43M). It's been a problem with the tractors since they came out. In cooler weather (<70F) it'll run all day w/o problems, but as soon as it gets warmer out, vapor lock sets in. The pump and carb are mounted high under the hood where all the hot air accumulates. It just boils the gas away. The ultimate solution is the 12V electric pump, which I haven't done yet. I wait till midnight to mow lawn... The Mikuni will probably solve your problem too. The only problem I can see is that mounting the Mik' away from the heat will require a longer pulse line if your vacuum pickup is up top near the carb. If the pulse line is the least bit flexible, it'll end up losing vacuum pressure. The old Gerber Racer was plumbed with copper . Pretty intense...

[jpswift1]

So Mike, what you're saying is that I could run a Mikuni pump away from the area of my Hustler where heat would build up if I used some copper tubing to ensure that I dont loose any vaccum? This sounds like a plan. I would be running the Hustler in 70+ degree heat.....especially when I take it in the Lake down at Sunset Bay and maybe in the Erie Canal if I get it done by then. I think that if I were experiencing vapor lock the Milfs would frown upon my machine.

[jpswift1]

Today after taking the BIGFOOT out for its big test ride I ran into two problems, first the wheel broke at the hub on the left rear and then, the engine had experienced what I believe to be vapor lock. It was about 80 degrees today and the engine was running fine for about 20 minutes or so and then it started running bad and then dying out. It would then start up after cooling down for a little bit and then die out again. I was running the machine with the back seat/ engine cover off too. Maybe its time for an engine swap?

[boncrshr]

Hey JP,

I have some extra axles and sprockets that I can't use...if you need them just say the word.

[Mike]

Jeff, are any of the fuel lines too close to the exhaust?

[jpswift1]

The fuel lines are actually on the total opposite side of the exhaust. I think the vapor lock could be occuring right at the fuel pump, which is mounted right on the carb which is under the air cleaner, and it seems to be a location where a lot of heat rises to.

[Roger S]

Was in a GM tune up classroom decades ago.. the teacher was old enough to have been a teen in the 30's. Was talking about vapor lock and how it had to occur in the line before it was pressurized. He told a story about being out with the boys in a car and a cooler of beer. The car vaporlocked; they poured a cold beer on the fuel pump and went on. This continued through the day. At some point they realized it made more sense to drink the beer and pee on the pump.

[liflod]

Same problem I have with my engine. I still haven't put a mikuni pump in line with the stock pump, but I think that will solve the problem. I have an electric pump that I run from an alligator clip. It works great with it running.

[hydromike]

Jeff,

Plan on it being vapor lock. I think I might have posted the same info earlier, but the Onan twins that use the older carb with the pump right on the carburetor are notorious for this. Almost every one does it after a hot day of mowing. The best solution that people have come up with is to either replace the carb altogether, or go with a remote (preferably electric) fuel pump. A simple 12V pulse pump would work well, and you can mount it anywhere. It should solve the issue pronto.

~m