Motorcycle Repair: Starting Problem, overflow pipes, suzuki intruder

Question
I just replaced the rear cylinder base gasket on my 1996, VS1400 suzuki Intruder.  After installing the engine and throughly charging the battery, I proceeded to start it. Before I did this, the engine ran fine but it was leaking oil quickly out the base rear gasket, once it warmed up, 10 mins.

On the first day, it sounded like it wanted to crank, but it seemed to die every time.  At that time, I noticed that gasoline was pouring out the overflow in the top carb. Not knowing what was happening, I kept pushing the startor button until the battery died.

Well I read in the clymer book, that the carb was flooded, so I drained the carbs, both of them.  Then charged the battery again.  In the process, I found that I had a damaged spark plug in the rear cylinder.

So here I am.  Charging the battery, waiting to get 2 new spark plugs.  Is there anything else I should be aware of?

The damaged spark plug is a mystery. My guess is it happened some time in the installation, but could the piston have done that? IF so, why and what should I do?

Answer
Hi Marcello,

Even without knowing/seeing the damage to the spark plug, I doubt that a psiton caused the damage. Valves would likely be damaged, too.

Carburetors overflow due to the following:
Worn needle valves
Varnished needle valves
Rust caught between needle valve and needle valve seat Improper float height
Split overflow pipes

I suspect the carburetors need thoroughly cleaned to remove varnishing. Especially if the MC was stored for any period with or without gasoline stabilizer.

After a tear-down reassembly, always verify engie rotation by hand. If engine rotates freely, check cylinder compression. This will determine the sealing properties of each combustion chamber and give you an idea of the condition of the engine.

Avoid pressesing the starter motor button longer than 5-10 seconds at a time to prevent burning the starter motor. If the engine doesn't start within the first couple of tries, there's a problem. Stop starting and find the cause.

Remember to retorque the cylinder head and camshaft bolts after the engine has reached operating temperatures a few times.

Respectfully,
Mark Shively