Briggs & Stratton Vangaurd

The B&S 21 Hp Vanguard engine in my ATV quick firing on one cylinder suddenly. Like as fast as between one stroke and the next.

In looking it over I found oil running down the front of the engine and presumed I'd blown something, but upon looking further that's the cylinder that's firing.

There is a problem there in that the spark plug wire internal connector is broken and the plug only connects by touching a piece of metal at the top.

The nice clean side is not firing. I pulled the plug and blasted it to give me a clean base line and that plug wire is connecting normally.

While I was down there I noticed that when it's running I have a bigger than I'm comfortable with gas leak running down the carb from a spot that is hidden from me.

When I put my hand down by the cylinders I feel a slight pulsation of gasses, but it's on both sides so I think it must just be a minor exhaust leak from when they put the new engine in rather than something being cracked or blown. This is a replacement engine that is about 3 years old, but with minimal running hours.

So where to begin? Carb? And where do you get carb kits or tune up kits for these things?

I haven't pulled the cover off so I can't see what kind of ignition system it has. Could it be down there (too)? And the gas leak is just coincidental & something I hadn't noticed before?

I have almost zero small engine experience other than throwing them away when they don't work anymore cause they are too much trouble to work on, but this is a $1,000+ motor.

I guess I should add that the carb appears to be 2 single barrel carbs joined at the hip. It appears from the outside that for convenience they just cast 2 individual carbs together so I'm guessing that they are separate systems. Of course the gas is leaking from the side that works.

Any small engine shop could help you out.

Have you checked for spark at the non-firing cylinder? If it's sparking, try swapping the plugs.

I swapped the plugs first thing and no difference. I put in an old set of plugs and it was no better. From the plugs you can tell which cylinder isn't firing.

I don't really want to take it to a small engine shop for several reasons 1) cost, I really figure it's something minor 2) at this time of the year it would be a month before I got it back and we use the thing around here a lot for gardening, hauling, etc.

I was hoping that someone was familiar with them and could quickly point me in a direction, but tomorrow I'll pull the shrouding off of it and go looking.

I need to find a tune up kit if for no other reason than to get another spark plug wire for the side that is firing. It's genesis is hidden behind the shroud so I'll see if I can bastardize a standard car wire, but I'm expecting an unusual termination.

As I write this I realize that I didn't really check for spark on the bad cylinder. I swapped plugs but I only checked for spark on the oily cylinder because I originally was so sure that was where the problem lay.

BUMP so that others than the weekend crowd will get the chance to help me.