King Cat overheating

[thomas2012]

Hi all, I used to be an avid rider till gas went through the roof. My son is now old enough to ride so were back in it. I purchased a 2003 mx?? 800
with 900 miles for him and a 05 King Cat with 1500 miles on a siezed engine for me. 3k for both.
My friend who sold them to me said that he rode the cat for about three hours b4 engine siezed. He topped off gas and oil b4 the ride. The gas was half empty and the oil was still topped off.
I tore motor dwn to crank and took all to machine shop. Crank/rods were good so I replaced bearing and main seals only and put case back together. One cly was fine some light alum build up and the pto side had alot more build up but both cleaned up great and didnt need resleeving. So I replaced pistons and rings and full gasket kit.
Put it all together and it fired after a few pulls. The motor seemed to shake more than normal at a low idle but once i reved it up a little it smoothed out. I ran it up and dwn the rode for about 5mins max it ran really smooth and sounded great but the temp warning lights came on and cly's were very hot. I let it cool dwn and started it again in my garage "mistake" just giving it little spurts of throttle and it heated up the cyl's again after about three mins. The hose up top was hot but the hose on bottom at water pump was cool. I tested thermostat and its working correctly.
Im thinking maybe an airlock in the cooling system. Does anyone know how to trouble shoot the cooling system or a way to bleed it? There is a smaller coolant hose that goes from the theromstat housing area to the carbs, what does that do? It has a red shut off valve before the carbs. It was in the off postion when i got it. I turned it to on while trying motor out after rebuild. i looked at some pics of my old 1M 900 sled and it was in the off position the whole time I had it.
I was also going to try bleeding my oil injection system, does that just include disconnecting hose from oil pump and lettinh oil drain until theres no air in fluid?

Thanks for any help/suggestions guys.
Thomas

 

[diggerdown]

The little hose is your carb heaters. It takes a while to bleed the systems out. Elevate the front of the sled so the engine is higher than the rear heat exchanger. I take the three bolts out of the thermostate housing and fill the engine with antifreeze. Put that back together and fill your reservior then run the engine for a while. Hopefully you have heat at the rear, then shut it off and leave the cap on tight. come back tomorrow and fill the reservoir jug again and heat it up then let it sit. Takes a few heating cooling cycles to get the air out and you need the front raised to get all the air out of the system. When you think yo got it all bled, make about a mile run with it and let it sit until it is cold, then check the coolant level again. If you are not getting circulation you will need to rebuild the water pump, I assume you checked the drive shaft when you were in the case.

 

[Rixster]

The 900s were pretty good at getting a air bubble in the cooling system. After a rebuild I always carried a bottle of coolant with me on the first ride or 2. Also, I like to pre mix my first tank after a rebuild at 100:1. just for a little extra protection.

 

[Meatman]

both good points....you have got to burp that system in order to keep everything running smoothly. Sounds like you're on the right track. Make sure that the heat exchanger is getting warm, if not then yes you have a bubble in your system, no worries, easy fix

 

[Arcticatdan]

It almost need to be vertical to get all air out.

 

[kcdavidak]

you can bleed the oil hose to the pump and then bleed the oil pump, there is a bleed screw on the pump. after a fresh rebuild I like to use a coat hanger and pull the oil lever wide open at idle for a few minutes.