Small Engines (Lawn Mowers, etc.): 16hp B&S columbia tractor, sae 30, shell rotella

Question
Hi I had a question about my old Columbia lawn tractor with a 16hp B&S single piston motor.
The numbers on the motor are 326431 0136-01 7502071.
My question... The engine runs good but sometimes if I pull the power quick, running full throttle then pull it down to idle it will let off a really good back fire !? I cleaned the carb and readjusted it as best as I could. What would cause this?


Also I was wondering what you thought about using Mobil 1 synthetic 10-30 oil in my tractor... well snowblower, lawn mower, 4 bikes (3dirt/1street) ;)

Thanks Wayne.

Answer
Have the valves ever been adjusted?  Have the points been replaced?  On that old of an engine I would check both items.  Do you have any experience working on small engine valves?

The oil is fine for your snowblower and you can run it in the mower during the winter.  During the summer I would recommend straight SAE-30 in the tractor.  As for the bikes, there are varing opinions on the oil.  I have ran synthetic in one of my street bikes but it did not seem to shift as well.  The biggest debate on the bikes is due to the clutch riding in the oil.  Some sites say not to use it because the synthetic can cause the clutch to slip.  Personally, I run standard Shell Rotella in most of my bike based on what I have read.  It is cheaper and I tend to change my oil more often than most so it is more economical for myself.
Let me know about the valve question.
Eric