We have a Toro model 74410 Z Master with about 1550 hours on it. Yesterday it ran fine for 2+ hours then started to smoke badly and make noise under the fan assembly. It still ran but when it was shut down it smoked for 10-15 minutes. The engine has gotten so hot that when we checked the oil about the last 1 to 1.5 inches of the dipstick was melted and also the insulation on the throttle and choke wires was melted to the point that they won't move once the mower cooled down. Any ideas on what happened? A blown heat gasket maybe but why would the oil get hot enough to melt the dipstick?
First thing You need to do is to remove the engine shroud and check to see if the cylinder fins are clear of debris. If everything is clean and clear post a couple of pics of the damage you are talking about.
When you have the blower housing off pull the flywheel & have a look at the alternator stator.
Debris gets in there and breaks the magnets which then jamb the flywheel turning it into a brake so it gets very hot .
The heat travels down the crankshaft and gets transferred to the oil ,
FYI - I do not wash my mowers. I use compressed air to blow them clean after every operation. I make a point of air blasting around the idling engine, through every opening I can find. I repeat this around the transaxle, deck & drive pulleys, chassis - when you know where the chaff tends to build up, this will be a quick & easy action, that will help to preserve & maintain the operation of your mower for many years into the future.
When I do my annual service, I remove all safety covers and air baffles and again using compressed air make sure everything is chaff & dust free (keep an eye open for mud wasp nest in cooling fins)
