I have recently finished restoring a 1978 cota 247, including engine rebuild etc etc. It is now road registered so have taken it out to my local woods for a few test rides, the journey there of about 1 mile on the road is fine, but when I have put it through its paces in the woods and hit the steep upward sections the engine goes into iddling mode which I think is called bogging. When switched off and left for a while it does restart and run ok. I have no idea whAts causing this and its putting me off doing some real trials - any help will be very much appreciated. David