Eagle1,

You can fix this very easily by going to your local motorcycle dealership and acquiring an exhaust spring for a two-stroke dirt bike. Simply install this spring in parallel with the weak OEM bonnet-popping spring. Adjusting the rubber bumpers will work as well but they really aren't meant for that - for one thing they don't store nearly as much energy as a spring - and with constant pressure they will fatigue and flatten out - they are actually for support and height adjustment of the bonnet - so that it's flush with the fenders. The spring is supposed to do the heavy lifting but obviously it's not up to the task since it seems many of us are having problems. If you're a purist, you can order a new OEM spring from Merlin but I suspect it will fail in a few years like your original. Exhaust springs are fairly robust so if you go that route I think your fix will last a while. Just pick a spring according to size - takes all of 10 seconds to install it and you'll never have to worry about it again.