I was going to guess air leak, until I read post two! If there's a split in any of those pipes, it's almost certainly drawing air and leaning off the mixture. Blipping the motor will be no problem, but under load it's a recipe for disaster! I've NEVER seen any of these pipes perish before. I would be inclined to think that they have come into contact with something (a cleaning agent maybe) that has reacted with the rubber. The only problem I have ever had was a fuel hose from the carbs to the tank, where it was a little loose at the union on the carb.

I would replace any split air corrector pipework (can't see any problem using silicone hose asa long as the seal is tight), check the inlet manifold is torqued down correctly, and that the carbs are seated properly and tightly clamped in the manifold. I'm assuming you used a new gasket on the crankcase side of the reed cages?
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Andy.
NSR-WORLD.COM

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