Hello,

What type of motor is this? Is this in an aircraft?

Just wondering if this is a 2-stroke fan cooled motor like in an ultralight or is it a 4-cycle motor like the 440 motorcycle motor.

You are correct. That engine was based on the snowmobile engine, but some changes were made.

I have worked on both the snowmobile version and the ultralight version. Let me say up front that I am not an aircraft tech, but I have been around long enough that I did go to Kawasaki snowmobile service school. I understand that engine very well and I should be able to help you out.

One thing to know up front is that your engine problem may suddenly develop into an engine seizure. Do not fly until you have the problem solved.

I think you have an air leak in the motor. I suspect it's the crankshaft seal. This will cause a loss of power in one cylinder and cause the other one to work harder and overheat.

I would do the following. Check your carb for dirt, water, etc. Verify that the manifold is not leaking. Also check to see if the exhaust gasket is leaking. If these checks find nothing, you should air test the motor. This is done by blocking the exhaust and intake. Air is pumped into the motor (use a fitting on the spark plug hole, or a fitting in the block off plate on the intake) and it is checked for leaks. You will want to use 8-10psi with a small hand pump. Have a gauge on it so you can shut off the air and read the gauge which will show any pressure loss. You should have none. Use soapy water to find any leaks. Repeat the test using a vacuum pump. This will test the seals in both directions.

If you have a leak in the crankshaft seal, the engine will not build proper pressure in the lower end and not send the charge to the top end. You can have a loss of power, a lean condition or other things along that line. Rapid engine seizure can happen with this condition.

Let me know what you have checked and if you will be able to check the engine for leaks. I would also do a compression test so you have a bench mark of the condition of your top end.

Excellent, you have base compression numbers to compare against new numbers. Recheck the motor now to see if there is any change. An exhaust leak at the cylinder will raise the exhaust temp while the head temp will stay near normal. You can have some scoring on the piston if the leak is bad enough. It's just something to check and rule out. I don't want you to go digging into the motor if it's just a simple problem like a bad gasket.

It's very common to see some oil seepage on that engine. It's only a problem if the gasket has failed and the engine is leaking air. On a two stroke engine it's critical that the engine hold air pressure. Unlike a 4-stroke engine, the 2-stroke uses the intake, exhaust and lower end in place of valves. It must be air tight or it won't work properly. One key is to use grease on the paper gaskets to seal them. If you use gasket sealer, they will leak. The paper gaskets will bond to the metal if you use grease instead of gasket sealer. It took me years to find this as the cure for gasket seepage on these motors. You do need gasket sealer on the exhaust gaskets. I use high temp Arctic Cat gasket sealer, but there are other brands that will work.

The only way to verify that a gasket leak is a problem, or if the seals leak, is to air test the motor. It takes some time, but it is the proper way to tell the condition of gaskets and seals when you are faced with an odd problem. You can use rubber corks to block off the exhaust, or make block off plates out of aluminum and put a rubber gasket on these. Be sure to check the impulse line to your fuel pump if you are running a vacuum operated fuel pump with an impulse line to the crankcase.

Are you in a local ultralight club? They might have a list of people you can use. Due to liability issues, most mechanics won't touch these. Any shop who works with snowmobile engines can do the test. I'm going to check with one of my buddies to see if he knows anyone in your area who can do this for you. He worked for Kawasaki for many years and knows everyone.

I'm going to switch this from chat to regular question. That will give me time to ask him and get back to you. You can still reply and ask additional question as needed.