I have a 2000 DS with six seasons of hard duning. Last trip I was riding very hard, we stopped because on of the rails had a minor problems. I looked down and had steam coming from a collant hose that had blown off on the left side of the head. I shut it down and kept the fan on while puttng the hose on. Prior to this event the motor had an unusual noise on the top end (very minor). I decided to go back to camp. babing it all the way back and stopping very few minutes to let it cool down.

When I got back I checked the radiator and it was bone dry. Added water and pulled thermostat thinking maybe it stuck close and pressurized the system blowing the hose off. So I started it back up and when the engine reved it pushed collant and air out the small hole on the top of the resevoir container. I shut it off, let it cool, tried to restart it....no luck. Pulled a plug and it was wet with coolant/H2O. Probably bad head gasket or cracked head.

Got back home, pulled the motor expecting to find a major problem......nothing, all gaskets intact, I can't see and crack in the head, piston looks great, cylinder wall looks awesome for 6 years! But about 2 quarts of coolant/dirty water in the exhaust system! LOL

What do you guys think, I wish I could find a critical failure so I know what the probelm is. I was planning a major overhaul/upgrade anyhow.

Also any advice of improvements and things to check on the bottom end while I have it down. I'm new to the 4 strokes, but I have rebuilt a couple of TRX/CR's motors, have service manual. I want to identify the problem before the rebuild.

Thanks

 

I had that same home blow off a few times when i was ridding, but always caught in time. I knew there had to be a reason why i carried a water pack - to fill the rad !!!

I did have to replace the hose and glue it with contact cement to get it to stay on.

On your motor problem - it is hard to say where the coolant came from if the gaskets looked good. I guess it is to far apart to do a compression test now right.

I just installed my big bore kit last year and my stock cylinder walls looked the same as yours - great after 5 years of ridding. There was nothing wrong with my motor, I went in to do the shift forks and did the big bore at the same time.

Wish I could be more help. Let me know how you make out.

 

What about a broken valve spring? I haven't looked at those closely. I know it doesn't explain the coolant in the exhaust, but maybe the upper valve train noise I heard prior to the failure?

 

The noise you heard could be the the Valve train. To take the valves out of the head you will need a special spring compressor. When I did mine I borrowed one from an old bike dealer.
Tried with a few other tools first - almost killed my self !!!

I just purchased one from Rocky Mountain to have just in case (tusk 19-6013).

I would also check the chain tensioner, that could have caused the noise you heard. Was the noise a rattle or more of a hard metal noise ???