Did I kill it?
 

So I overheated the K301 in my 125 the other day while mowing. It started to bog down and blow smoke. I shut it down and saw that it had overheated pretty bad. The gas was near boiling in the tank. So I pulled the shroud off and cleaned some grass out. While I was at it, adjusted the timing to see if that would help also. When I started it back up, it makes a horrible sort of squealing sound as I crank it. It almost impossible to start, but when it does, The squealing speeds up with the engine. Any ideas? I was thinking maybe head gasket air leak?

My guess is that you may have scored the piston. I'd take the head off and take a look at the cylinder.

Also, you may have scoured the Connecting Rod /Crank Journal....:Shocked:

This maybe a tear down and rebuild situation.

YEP!!!

You didn't "kill" it, but it's hurt... Yank it out before it gets worse and gets deeper into your bank account! Kohler cranks cost a fortune!!! (ask me how I know)!

So I pulled the head off today and this is what I found. Definitely blew the gasket but the cylinder walls look great (this is a fresh rebuild with about 50 hours on it) no signs of any scoring or abnormal wear. Now that the head is off, it doesn't make noise when I turn it over any more, which makes me thinks what I was hearing was the air leak coming through the gasket. Given what you guys see, do you still think I should tear it down? Everything sounds good internally.

Another pic of the head and gasket

If the crank assembly is able to be turned freely by hand and you don't feel any significant drag it should be fine. Just a quick question. After the new build, did you re-torque the head after the first 20 minutes of letting the engine run at different RPM's? If not, this might be why you blew a head gasket. I would clean up the carbon deposits on the valve and the head also.

make sure you retorque the head after you run it up to temp. it helps prevent that.

You might want to deck the head again. It shows where you had a blown head gasket, which may be related to the head being warped. Also it would not hurt to take a head bolt and run it into the two closest bolt holes on the block to make sure the bolt can go all the way into the hole to bottom and both holes are the same depth.

Yup, I had retorqued everything three times while breaking it in. The gasket was genuine kohler, and I had decked the head with 320 grit on a glass plate prior to installing. I used copper spray a gasket sealant for good measure also. I guess I'll just have to repeat the process and hope it takes. Maybe the heat was just to much and warped the head.

Okay, so I'm completely lost. I cleaned up the head with 220 grit sandpaper and put in a new gasket. Fired right up with no squeal. However, I think it is still running too hot. I'm not familiar with how they normally run, but within 5 minutes of running at fast idle, the front grill housing and engine block are too hot to touch. Also, it runs rough, and seems to be missing/hunting when I run it up to speed. Here's the full history of the engine:

Rebuilt 6 months ago (new crank, rod, piston, rings, .20 over, valves lapped in)
New points, and Kirk Point Saver system with Bosch coil
Rebuilt carb (main needle, gaskets, throttle shaft, float needle and bushing)
Plug is 6 months old

Here's what I have checked so far

Remover tins and cleaned cooling fins
New head gasket
Checked valve clearances (.09 intake and .18 exhaust)
Timing (easy with the Point saver, Light comes on exactly at the S mark)
Plug gap (.035)
Took carb apart this morning and cleaned it all out (there was some sediment in the bowl), also cleaned out fuel sediment filter on tank (had some sediment in it)
Set carb for factory settings (2 1/4 on main and 1 3/4 on low speed)

Any ideas on what it could be? I'm about ready to sell the thing. I've put a ton of money into it and there always seems to be something new.

Here a link to a video of it running
http://s1266.photobucket.com/user/cs..._0171.mp4.html

Sounds like it may be a bit lean. How are the bushings on the throttle shaft? :bigthink:

Will too much back-pressure do that? The exhaust pipe looks pinched off at the end, and the reduced flow might be creating a little too much... I'm no expert, but thought I'd throw in my $0.02.

I have no idea what your going by to say its running hot. After 5 minuets of running the engine SHOULD be too hot to touch. It's a motor, it gets HOT when it runs. As far as the motor not running right, from your pic of the engine with the head off, looks like its running WAY too rich. Both valves were black with soot. Especially the intake. Some of that may have come from when the head gasket blew, but from what I see, it looks pretty thick. You need to adjust the carburetor. I have no idea what a Bosch point saver is... or why you would put a Bosch coil on it. I have worked on thousands of motors, and it's been my experience on a regular stock motor of ANY kind, that when you screw around with "hopping up" the ignition, you only create problems. I suggest a Kohler coil, points and condensor.

HOT
 

:bigthink:I'm not sure if anyone mentioned this, but make sure the cooling fins are free of grass and cruds... especially by the exhaust valve. Should have a good flow of air coming from the flywheel.