jonzee

hi i have a 89' TDR 250, iv stripped an repaired her engine may times but i have one problem im confused about, after 3-4 mins ride i lose power then she runs on 1 cylinder, iv changed fluids, cleaned carbs and checked spark but its the same. iv got a small leak in gear oil seal but everything else is tip top. please help cos the missus is on my case for spending to much time with it. thanx