Had my 500 HO out yesterday and man this has me baffled I really get on it hard and about 35 miles an hour it has great power then it just goes flat then it has power then it goes flat and continues this way could this be a gas problem or a plug that is breaking down??????

 

If I was you I would first check your vent hose on your tank. Simple things first... Then see if your filters in your tank are clear of junk. Then work your way to the carb. It sounds like your not getting enough fuel into the bowl of your carb.

 

Was the fuel on?

That happened to me. Good luck with whatever the probelm is.