My 1982 XT200 (has same engine as TW200) has 4300 miles on it. Anyway, the other day I loosened the clamps attaching the carburetor to the airbox boot and the intake manifold. The boot had been barely attached to the carburetor. Does one get shrinkage of the rubber boot after several decades? The rubber appears healthy and pliable. The existing clamp actually is not the best as I had to hold the nut with pliers to loosen it. So I'm going to replace that clamp with one that holds the nut so it doesn't turn. The only way I'll be able to get good overlap of the rubber on the carburetor is to loosen the hex screws holding the intake manifold onto the cylinder before I attach carburetor to the airbox boot and the intake manifold. Hopefully it will stretch enough allow enough rubber overlap and keep it from leaking air.
I removed the rubber boot connector last night. The Yamaha parts people told me it is supposed to be 113 mm long. I measured it and it comes to about 110 mm. So it seems to have shrunk a bit. The bad news is that this part has been discontinued by Yamaha. Any suggestions? First I'll put everything back together attach it to the carburetor nicely, attach the carburetor to the rubber intake manifold, but leave the intake manifold disconnected from the engine. After the carb is attached well on both sides, then I'll thread the screws on to the engine and then see if the connections remain good when the two hex screws for the intake manifold are tight.
I looked at Ebay the other day and all the boots there are used and likely shrunk too. Any other sites on the web I might try?
You could try a heat gun before stretching it with the manifold bolts.