Bought second hand bike runs well enough 4x4 was working fine until I noticed battery died 3 weeks later so charged battery back up bike worked fine but to find battery cell had blown, so I bought a new battery all 4x4 was working again for about 3 weeks then decided to disingage after a minute , the battery is fine charge coming back but 4x4 goes on then off but won't come back on unless bike is powered off then back on at key! Any solutions please

 

One of the two speed sensors on the front diff will have failed. If the speedo still works it will be the front one. The sensors have to agree, if they don't by the time the speed has reached (I think 7mph) the fail safe cuts the 4WD mechanism until you switch the bike off then on again. The test is to swap the plugs into the wiring loom for the two sensors (they are identical but colour coded) behind the LH front wheel, the speedo will then fail to work (if it did before), but the 4WD will still cut once that critical speed is reached. Also a fault code will flash in Morse on the 4WD light.