Bad knocking! WR400

I had something strange happen over the weekend. I was out in the desert doing a big loop. About 75 miles into it my WR400 started making a very bad knocking noise from inside the engine. I stopped to check it out. It wasn't boiling over and there was plenty of oil in it. It sounded like one of the bearings in the connecting rod had blown out, knocking each time the piston went up and down. I started and stopped the bike a few times. I decided to try to limp it to the nearest road, started it up and while I was turning around, the knocking totally cleared up. Since I still had 25 miles to go, I went for it. The bike ran just how it should!?! What was that?!! I haven't been able to check into it yet. I'm going to drain the oil and see if there are metal pieces in it. Any comments?

Wow, may be a flywheel or someting came loose? I know earlier models had some oil pump gear or water pump gear or someting that were known to come loose. Sounds like someting like that may have come loose and then seated when it cooled down?

I can't imagine what made the noise. I guess I'll have to pull off some covers and see if something came loose. It is running fine right now but I'm a bit nervous to go deep into the desert with it untill I find out what's up. Anyone else? Help!!

Carbon Knock sometimes carbon build-up in the combustion chamber breaks loose and knocks around until it blows out the exhaust. I have seen this happen on several cars and it sounds just like a rod knock. I would go to a GM dealership and get a can of Top Engine Cleaner and follow the directions first and then if you still have a problem tear apart the motor.

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