Overheating symtoms ?

[yukon254]

I've got a Bearcat wide track with the 2-stroke 570 fan cooled engine. Did a long run in warm temps. It was raining! Anyway machine ran fine until I was 5-miles from the truck. The first time it bogged down like it was running out of fuel. I stopped, shut it off checked fuel, it was OK so restarted. Machine started right up and I went another mile or so and it died. I took the hood off had a quick look but couldnt see anything obvious. I had to choke it to get it going that time, but it did start. Ran it with the hood off the rest of the way to the truck ( about 2-miles) and it ran fine. My first thought was overheating, but I cant figure out why it ran so good all day. I ran it 55 miles that day and only had problems the last few miles. Any ideas would be appreciated.

[Okotok]

Fuel filter?

[Dean2]

On a warm day is the plug could be breaking down. First step would be a new plug. The most likely issue is fuel. Something is causing fuel starvation or too much air in the mixture. Having to choke a hot engine is usually the result of too little fuel. Check fuel line, filter, carb etc. Something is reducing your fuel flow. May also be that your fuel pickup in the tank isn't all the way to the bottom and when the tank gets low, especially on hills or rough ground you are getting fuel starvation. Fuel system is where I would start looking.

[Joe Black]

sounds like you may have burnt one side out.

once it cools down, specs tighten up, runs ok till heats up. opens up. looses compression, bogs

do a compression test. pull both plugs, connect one side, hold throttle open for 5 pulls. should be 110-130 per side. if both sides are not the same(one really low) top end rebuild time.

another less sophisticated way is slowly pull the engine over and see if one of the compression stroke is easier to pull over than the other while keeping a constant pull on it.

could be fuel pump/filter, but compression check will tell you what it is(or not). with the engine itself. may be junk in the carb if you dont have a fuel filter.

[Drewski Canuck]

End of day is the hottest part of the day. You likely have a Carb machine that is jetted for a set altitude / temperature range.

Pretty hart to overheat a fan cooled engine unless the fan has in fact seized or the hood was plugged with weeds / cat tails, etc.

There is alot of air flow on these hoods.

If it is truly oveheated, you should see some paint damage on the block.

However, a quick compression test will give you your answer.

Is it possible that you were down to the bottom of your tank at the end of the day and you have some junk in the tank that is now plugging things up? Some units have a "screen" on the pickup hose, and depending who filled the sled up and with what, there could be some debris in the tank.

I have a VK540 that was loved hard before I got it, and we went to the point of removing the tank and flushing it out and drying it before putting in new lines and filters in. The Carb has a "welsh plug" which is a little silver disc, that sits over the venturi that distributes the to the different jets, and it was filled with black stuff as well. No amount of Carb Cleaner could dissolve that stuff, and it was because of dirt in the tank and no fuel filter in line.

Any ways, good luck on this.

Drewski

[Steyr Luxus]

I agree with Drewski Canuck a Carb machine that is jetted for a set altitude / temperature range.

[Fish along]

Sounds like water in the fuel