My brother in law has a 1986 XL250R. We raced before I put my slip on and he was going way ahead of me (both bikes in stock form). I installed my two bros.then we tried again and I was surprised to see that I cannow follow him. Makes me believe that only a slip on does improve something... I had to stop mods because of my wallet but still have to do the jetting and the 13t cs. Hope to do it soon. Can't wait to race him again after the other mods to see the difference.

 

Of course a slip on makes way more power But word of warning you should not even be riding without jetting let alone racing it.......these bikes are VERY VERY LEAN to start with the jet kit is not a lot of money ....do yourself a favor and do it asap
GOOD LUCK

 

+1 get a jet kit on there, its cheaper than a burnt piston or valves.

 

On mine I whent from a 14 to a 15 sproket...The added torque from the 300 kit give me plenty of torque.