Engine lunges with each chuff when smoke is on

Sounds like the smoke motor is drawing excessive current and loading down the 5V supply.  Time to do some smoke unit maintenance.  I'd also examine the wiring from the board to the smoke unit carefully to make sure nothing is shorted or grounded.

Hi John,

I did inspect the the reservoir and wick, everything looked good. Nothing charred, plenty of fluid. I forgot to check and see if the fan ran when turning the smoke unit on. Wires look tight, nothing melted to ground or shorted. Could a bad smoke fan motor cause this? Would it hurt to try running the engine with a disconnected fan motor?

Thanks 

OK, did some further testing. The fan doesn't spin but it isn't seized, it turns freely by hand. When I disconnected the fan motor, the engine takes off at 2 SMPH, and there is no chuffing, only the usual sounds that play while the engine is stopped/idle. With the fan motor disconnected, there is a 1.4 amp draw, and pressing smoke button on or off has no effect on the speed or the amp draw. When I plugged the motor back in, the chuffing came back, and the engine reverts back to the behavior as described in my original post. Disconnecting the smoke elements has no affect on the speed, sounds, or amp draw. I could check if there is power going to the heat elements but need to know if that current is ac or dc.

Well, since the smoke motor isn't running, and it's affecting the operation, first step is to replace the smoke motor.  I believe that's all you'll need to do.

To see if power is going to the smoke elements, just feel the top of the smoke unit.  It'll be plenty hot with smoke on and no smoke fan.

Nope.  A disconnected smoke unit should not stop chuffing.  I believe you have a broken wire to the tach unit, probably the ground line.  When the fan gets pulse it feeds back enough voltage to the tach to get a signal to generate a chuff since they share the 5V line.

Replace the tether. BC-0000217 since this is an easy fix with the detachable external tether.

If that fan does not run it may be bad also so replace it too.  BUT Does the motor spin when power applied (disconnected from board)  May just be a loose impeller on the shaft.  Dot of superglue will fix that.  BE-0000041 is fan motor.  G