my brothers prairie 650 4wd wont engage, if he puts it in 4wd and drives around a bit it doesnt engage. He left the key on for a while and needed to pull start it, could the battery being drained down cause the 4wd to not engage. I thought it was an electric servo that switchs it into 4wd and the battery being drained was my guess it wasnt engaging.

 

charge the battery and try it again if that doesnt fix it it maybe the servo motor.

 

does the quad take of on its own like with out touching the gas
if it does it could be the actuator
im not sure tho let me know if that help's

 

Disconnect the KEBC servo, then try. Mine goes into 4wd instantly with it unhooked.