Went to crank my John Deer Mower today, & the V-twin 18hp., Onan backfired, upon cranking. Don't recall that before. Then mowing the front yard, I knew it was running right. Trying to speed up & down. I finished that went to idle down, & engine died. I had 1 more spot to mow, so I found a can of B-12 Chemtool Fuel Treatment, my Brother brought to me, while I was having ethanol problems with the CJ. Product is to be mixed 1oz - to 1 gal. I've got about 7-8 oz.s left, so I dumped it in about 4 gal., in the mower tank. Whatever it was, trash, water, ect., Mr. Onan, cleared up in about 5 minutes! Makes me Happy, because other than a couple of fuel filters, my fuel system has not been touched, in 24 years!