Kawasaki in a Deere

[john hall]

The following is a copy of a PM I sent to JMech. After sending it I thought this one may be a good brain teaser for members at large. Anyway, here it is:

Leave it to me to get another headache in the shop. Working on a 17hp single cylinder Kawasaki in a Deere mower. Engine is running HOT--so hot it shuts off/runs rough after 15-25 minutes. So hot it dropped a valve seat. I have replaced all fuel lines and cleaned fuel tank. Put on a new carb solenoid--was working intermittently. New spark plug. Engine is spotless. Flywheel key is fine (put in a new one anyway).

So me and some mechanic friends are thinking must be the coil/igniter combo (igniter is not a separate unit). Using the Deere service manual, old coil did not test out well. Bought a new coil and it bench tests fine. bolted it in and for the heck of it checked one more time, now it ohms way out of spec--its weird, it ohms way high, around 1200K, but falls to 950 (using 2 different meters). Book value is around 20K. I'm confused, why is it not reading correct now? could being near the magnet "charge" something like an old school condenser?

Would you just bolt it together and see what happens? FWIW, it cranks and runs fine, plenty of power but when it gets hot it will either die, sputter/surge/ or spark knock--even seen the oil light come on at low RPM--think its that hot. My temp gauge reads 350F on the carb bowl (carb is 2 inches above muffler. FWIW, mower is pristine, all original, no heat shields missing. an absolutely pampered one owner machine. Got any thoughts? 3 genuine Deere mechanics are stumped. No its not mine, helping my cousin.

Oh yeah, I have even poured water on the fuel pump and opened the fuel cap thinking that was the issue, no change.

[Lance Skene]

Assuming youve already checked for proper airflow under the tins, and the crankcase vent, then yes put it together with a new coil. I change ALOT of coils on small engines, I dont think Ive seen one that directly causes an engine to run hot but often a coil will work fine until the engine, and the coil warm up. Then it may misfire and subsequently an engine that isnt running properly can run hotter than normal so the problem can magnify as the engine continues to run.

Im curious if your using a digital meter because I just read a post recently where someone recommended using an analog meter to test a coil??? Personally I own both type but to test coil/spark I use a timing light... if the coil is bad then the spark will get more erratic as the engine warms up.

[john hall]

Lance, the reason we are suspecting the coil is that the igniter is built in, guessing that can affect timing (flywheel key was fine) ?
Both meters I am using are digital.
Yes, the engine is absolutely spotless--literally nothing to clean off when I started working on it.

[Lance Skene]

The trigger is activated by the magnets in the flywheel so it cant go out of time with a good key in it. Im not sure what the deal is with the digital meters... I just happened to read a thread on another forum recently and someone mentioned the readings being all over the place. I have a couple of those Kawi engines over at a landscape company and I did have to change a coil on one of them a couple years ago... now its bending pushrods so I expect a valve guide is loose... which would be another heat related issue. Not that they are bad engines... but those landscapers are hard on them

[john hall]

Think I found it. Put the new coil in tonight and had it idling in the shop. Closed the hood and heard a change in sound, like something was rubbing. Raised/lowered the hood a couple times then looked to investigate. Deere used a 2 piece hood that has a giant air chamber complete with a spring loaded baffle for air flow. Well they either wanted to dampen vibration into all that plastic, keep down noise, or keep heat off the top of the hood. Anyway the insulation material has a foil side facing the engine. Time has taken a toll on the glue and let it turn loose, filling up the air chamber and even plugging the outlet to the point it was hitting the flywheel screen--couple small holes in it. I think removal of this is gonna let things run a LOT cooler and the fuel and ignitions systems should appreciate it.

[Lance Skene]

Oh ya... that will do it... should be good to go now.

I worked on an LX277 with a similar hood design a couple years ago... the hired help at the landscape co had loaded the tractor backwards on the trailer and lost the hood... that was about $1000 blown in the wind