SX/SXi/SXi Pro Engine Head gasket / overheat...

M

myboating

Location
michigan
Hello,

My sx 750 overheated and turned the top of my engine black. I think it blew the head gasket, but i am not sure why. I took off the heads the looked at the head gasket, i will post pictures today as well, and it was slightly bent, but im not sure what it is supposed to look like.

I had a problem with all the blots coming out of the exhaust flange the day before for some reason, and put the high temp sealant between the flanges and bolted it back together. Any it looks like on the inside of the cylinder walls there are small reddish flakes i can wipe off, i dont know if it could be part of the sealant somehow leaked back into the motor or what? I am not sure since the exhaust flange came off it it occured because the motor overheated and it backed out the bolts, or maybe when the exhaust came loose, it is screwed up the compression and blew the head gasket which caused it to overheat the next day? Can it overhead if the head gasket is not sealing properly?

Also for engine cooling, is there a pump to pump water to the motor, or does it shoot it from the jet? Any help to go through the cooling system to ensure that it is working properly would be great.

Thanks
 
Waternut

Waternut

Customizing addict
Location
Macon, GA
You cooling comes from the stator veins in the jet pump. It has plenty of pressure but it's dependent on rpms.

The head gasket is made of thin metal so it will look bent. Once you crush it though, it's straightens out. If you see black soot on the head gasket in an area between the water jackets and cylinder, you probably did blow it and the head or cylinder is warped. If you blew the head gasket, it could've been from heat but most likely the engine overheated because you blew the head gasket. The engine overheats because the cooling water goes into the cylinder instead of actually cooling the engine, head, and exhaust. The best way to check your head and cylinder is to put a thick piece of glass on them and see if all points are being contacted. If not, tape some 200-300 grit sand paper to the glass and start hand sanding the little imperfections out. Make sure to sand evenly over the entire surface. You'll have to pull the studs off the cylinder to check that but with some effort, you'll eliminate the problem.
 
M

myboating

Location
michigan
Cooling

There is a tube from the top of the motor to the top of the exhaust. Is that for cooling water? If so, what stops it from flooding into the cylinders. My cylinders had alot of water in them. Also, if water got into the cylinders via the carb could that cause a engine to overheat as well?
 
Waternut

Waternut

Customizing addict
Location
Macon, GA
The tube on top of the head is for cooling water. The head gasket prevents that water from getting into the combustion chamber. The area around the combustion chamber are called water jackets. The head gaskets is designed to create a seal between the two so that they don't mix.

If water got into the carb, not only would it not overheat but it wouldn't even run. If you get water into the combustion chamber where the pistons are, you hydrolock the engine. Air is compressible and that is how you get combustion. Water is not compressible so when the piston travels up, it stops and locks the engine up because it can't compress the water.

There are quite a few things that can cause you to blow the head gasket. You can hydrolock the engine and this will create excessive pressure on the head gasket which may blow it. If you overheat the engine it could warp the mating surfaces which creates an excessive gap between the surfaces and weakens the seal of the head gasket. Lastly, if the bolts are torqued wrong or were torqued in the wrong sequence, this can also warp the mating surfaces.
 
M

myboating

Location
michigan
When i pull the plugs, the pistons move freely, but there is alot of mist coming from them?? I am not sure if that is just from the water in the cylinders and there are still droplets that mist when they move or what? Also, how do i check if there is water in the crankcase?

Thanks
 
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