No, you don't have to take the motor apart to put in a replacement. You would have to take one side (I believe) of the rocker assembly off. The tube assembly slides onto it, and the metal tube fits into a hole in the head. It wouldn't be that hard to replace it. The valves may not even need to be readjusted - if they did, they wouldn't be off by much. I would just replace it instead of trying to braze it. I'd have to dig around, but I think I have an extra one somewhere - put an ad in the parts wanted section - I'm sure there's plenty of those around.
Samantha
