me and my father both have 03 prairie 650's when we were both stock mine was a tad faster than his now i have 26x10 and 26x12 mud lights, EPI black spring, and a DYNA CDI,.. and he has 26x10 and 26x12 bear claws and a hole shot module. this was the first time we have raced in over a year (sence i dont the mods) and with a 170lb rider on mine and a 195lb rider on his, I get the hole shot on him but by 20 feet he has already passed me and by 300 feet he is about 4 quad lenths ahead of me. in the same 300 feet right after i did the mods i could hit 53 to 55 mph and now i only hit 47 mph... what is wrong? could it be my belt? i have over 2500 miles on the stock belt but it isent churping or andthing..... help me

 

Thats alot of miles for the kawi belt. Is it the 700 belt I hear they were faster on top end on the 650's.The module your father has is good for just that, the hole shot ,I had the HL module on mine great on take off , Also had red primary spring , I was beating my buddy on his 700 pol out of the hole and he could not catch me in 300' . But yes check your belt 1st.

 

The Black EPI spring will slow you down a lot. Its great for trails, big tires and helps the belt last. But it will slow you down a lot. My 650 P read 72mph on a strip of road and 77mph in CA at Glamis on a down hill run. After I installed the Black spring my speed drop to 67mph on road and 71mph at Glamis. While at Glamis I ate two Dayco belts, but the Kaw belt lasted the trip.
I could out run 400EX before spring and couldn't after. And after 4000 miles with the Black spring both clutch shives were worn out to the point of belt replacement every 100 miles.
The Black spring holds more tention on belt for less slippage decreasing top speed and increase wear on shives.
I put new clutches on the 650 for around $800.00, removed Black spring and went to stock, shimmed rear clutch so belt was tight enough to squeal when stopped in gear. Just leave in netural until ready to roll. This makes the Kaw responed quicker and belt last longer.