[Dukedesmo]

I don't think they need to be changed every 2 years. Sure that's the recommendation but I'm sure they'd last much longer.

On the 4 valve engines there is much more of a reverse bend around the tensioner pulley and so presumably more stressed. Also compared to a car, they run faster and (likely) hotter, combine that with the small cam pulleys (as above) and some allowances should be made.

I think a lot of the hysteria comes from 4-valve engines in the early days suffering broken belts but I think that is no where near as prevalent now due to better belts etc.

I do mine at 3 year intervals and even that is probably overkill on the Monster? but, having last year dealt with the consequences of a broken cambelt on my Son's car I'd prefer not to take too many chances because if one does break it will not be good.

To quote Mr. Eastwood - you have to ask yourself, do you feel lucky? well do you?...