i just bought a new 07 rincon and as i was picking it up at the daelership we started it and it ran ruff as hell (about 38 degrees F).. i told the salesman that something wasnt right and he disagreed so we went and started another one that was inside it ran smooth. to make a long story short plug was fouled and i talked to the mechanic about it ..i was told that there was a packing lube inside the fuel tank that would take a few tanks of gasoline to clean out.. hope this helps

 

Yeah, my 07 has done this a couple of times only when it was real cold outside. If I tried to start it without giving it any throttle, it would almost start but you could tell it wanted more fuel. If I gave it any fuel the engine would crank a couple of revolutions and then it would stop quickly due to a spark that was premature. This would really stress the starter you could hear. Also it would backfire out the exhaust violently. I pulled the plug and it looked perfect. After a while I managed to get it started and all is fine thereafter. It definitely seems as though the problem is caused by starting the engine when it is very cold outside and then trying to put it in gear too soon. I think the Rincon's fuel injection system is good, but it isn't a very sophisticated one. It doesn't have a feedback function, meaning it can't make slight fuel mixture adjustments. It can only look up a preprogrammed map of what the fuel mixture requirements "should be" under every possible operating scenario.

 

The Rincon's injection system is a mapped, or open loop system, as are many offroad injection systems and older cars. It doesn't have an oxygen sensor to get feedback that a closed loop injection system has, so although it can compensate for ambient air pressure and temp, it doesn't compensate for any change in the engine's efficiency (like a performance muffler and intake, or conversly a badly clogged filter).

It does seem, especially with a new engine where the rings aren't fully seated, that starting it briefly a couple of times in cold weather will often lead to a fouled plug. Mine's never done that, though.

They also seem sensitive to marginal battery. There've been several threads about them seeming to crank over fine and not starting, and then firing up fine once the battery cables are tightened or the machine is jumped from another vehicle.

Lastly, the Rincon's transmission is designed to run in motor oil, which is higher viscosity than they typical automatic transmission fluid. It does fine, but in really cold temps it seems to need to warm up a couple of minutes before it will shift well, especially if you don't run a lighter weight oil in the winter. The 650 was more fussy about warming up, and as I understand it the oil passages to the transmission in the 680 have been enlarged for better flow through the valve body when the oil is cold.