Just wondering what is normal? When I start the bike and the engine is cold it will knock enough to both hear and feel in the handlebars. It seems worse when the air temp is cold. After it is warm it is very smooth and a wonderful ride. I use mostly 87 octane but I will mix in 93 on occasion (I really don't want to start an octane war). I live at sea level and it is usually humid, but not on today's ride when I noticed it again. Is this normal?