I have a Brute Force 750, starts OK but runs rough after a few minutes, will start smoking a smelly black/gray smoke, and most recently some blue smoke.

This is usually caused by a bad crankshaft postion sensor.

White smoke comes from water, blue from burning oil and black from too rich a fuel mixture. If the engine was running before the oil change occurred then perhaps you put in far too much oil. This can force oil past seals and into the combustion chamber resulting in thick smoke. Carefully check the oil level on the dip stick for the correct fill level. If there is too much you must remove the overfill. If oil has entered the combustion chamber the plugs may be fouled. Pull one out and examine it. If it is not gray and clean you must clean them all before the spark will jump the gap and the engine can run. If the engine did not run before there is a great chance , based on white smoke, that water is entering the combustion chamber.

If your after market turbo is blowing oil into the engine, best you have it removed. When you say that fuel may be leaking into the cylinders, it could be leaking fuel injectors. If the smoke out of the tail pipe, it's usually indicator of burning coolant. Blue smoke is indicator of fuel and black of oil.

somthing in the ignition is causing a weak spark--or fuel inject circuit is running to rich----------all causes improper burning---------get a computer diagnostic done

black smoke - oil in the cylinders

White smoke - water in the wrong area - probably a head gasket.

The head gasket is what I am hoping for because it is cheaper to do. And most instructions manuals from an autoparts store has step by step instructions.

If it is oil then you are looking at rebuilding or replacing your engine.

Take a look at both the oil and antifreeze to check for cross contamination which would verify the blown head gasket.

Exhaust problems. Black smoke=exhaust, blue smoke=oil, white smoke=water.

You mean lots of smoke? White, blue, black? Or just smelly stuff? Rotten eggs or shotgun shells, usually an oxygen sensor. I will give you the rundown, white smoke when first starts up is gas, should clear up in a minute.No big deal, normal. Black smoke, carbon, burning rich, settings are way off, computer is not right, oxygen sensors or air flow sensors are bad. Blue smoke is oil, you have lost comp and oil is getting into the cyclinders. Steam, comes out after it warms up and is a blown head gasket. You can look for oil in the radiator. A radiator shop can tell you if it is blown or not. Hope this helps.

Ouch! you've got engine coolant in the exhaust from a leak somewhere...DO NOT run this engine until you get someone (dealer is best in this instance) to diagnose ($50-125)

hey
there are couple of smoke type.blue smoke is oil, black smoke is fuel, and white smoke is water, if it clears after starting and running a few minutes it's probably your valve guide seals leaking oil down on top of your pistons, causing it to smoke until burned off and foul your plugs.