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Discussion Starter #1
Thanks for all of your guys help recently...

Same sled, 1974 Arctic Cat Panther 340

- I ran it no problem last night, 30 mph for 5 min.
- Took it onto a straight away and got up to 50mph for about 600 feet.
- At the 600 foot mark going 60mph I heard a screech from under the hood and then the motor cut out.
- Tried to start it right away and could not get it to fire. It turned over just fine but no ignition.
- Waited about 1 min and 30 sec. and cranked again. Slowly it started... sputtered and then got up to idle speed.
- Took it slow home, about 600 more feet and shut it down.
- Looked under the hood and saw that there was some oil / fuel coming out of the engine where the head meets the motor near the clutch.

Loose head? But what would cause the screech noise?

Thoughts about what the problem could be?
 

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Screeching sounds usually come from metal to metal contact between the piston and the cylinder. Lack of lubrication or overheating can cause it. Usually, it costs a piston, sometimes a piston and a cylinder. Pull the exhaust and look inside, you may be able to see if the piston skirts are damaged. Pull the spark plugs and put the piston to bottom dead center, that should allow you to look at most of the cyklinder walls. Screeching sounds are usually expensive :(

It could also be a bearing in the crank, but those normally make grinding noises.
 

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Discussion Starter #3
Why would the motor cut out and not start for a min or so after stopping? Heat?

Could my exhaust be plugged? Should I stop messing with it (and possibly doing more damage) and just rebuild the engine this summer?
 

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Lack of lubrication can cause metal to metal contact, and sometimes transfer of metal from the piston to the cylinder. Lack of cooling can cause the pistons to expand greater than the design, leading to displacement of the lubrication on the cylinder walls. Both of those will cause a squeaking sound in the engine, followed by the engine dying. It's not a sound you want to hear.

You should be able to pull the carbs, exhaust, and plugs and have a look at the piston skirts on the intake and exhaust sides and the piston crown as well as the cylinder. Use a small, bright flashlight and look at the cylinder walls. If you see damage, metal transfer, gouging, or other problems, the engine will need some work. Caught early, the cylinders may be ok. If you keep running it on bad cylinders/pistons, more damage occurs, costing more to fix.

The motor will start again after a few minutes because the piston has had a chance to cool down. Eventually, the damage will lead to lack of compression that is so great there won't be enough compression for the engine to run.
 

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Discussion Starter #5
Possible?

So I put the sled up on a jack stand last night. I ran it at 50 mph for 3 miles without a problem on the stand. I did notice the the clutch had closed enough that the belt was 1/4 of its thickness above the clutch (possible source of screeching if it hits the belt guard).

Put the sled on the ground and drove it 1500 feet to the back of my property turned around and 3/4 of the way back it died. Pulled the plug, good spark.

I am going to do a compression test as soon as it dies again.

I think my next step is going to be pulling the metal on top of the engine and seeing if the heads and jugs are tight or loose.

I may be waiting until summer to rebuild or find a used engine to swap out...

Thoughts?
 
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