Firstly - to XT660.com Dean.

Sorry to hear about your woes. Doesn't sound good?

However, looking on the bright side, cylinder head gasket failures are rare on the XT engine, in fact I don't think I've ever heard of one? One (cheap) thing to check is the radiator cap. There have been a few cases of dodgy ones in the past. Try a new one.

If the rad cap isn't holding pressure the coolant will boil at a much lower temperature than it should do in a pressurised system. Also if the cap isn't sealing properly the coolant system will be permanently venting to the expansion tank.

The brownish colour of the coolant is a worry as it would suggest to me that someone in the past has possibly added Rad Weld, Stop Leak, or some other quick fix additive to solve a leak or previous cooling issue.

Drain and flush all the old coolant out and refill. Then ride it and see if it turns brown again. If it doesn't, then you'll know that it was an additive causing the brown staining.

I hope it turns out to be something simple...

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