I was wondering if anybody had any ideas on what this could be. Every time I go up a hill or am pulling something, I get a clunking noise that sounds like it is coming from the front end, maybe the 4wd actuator, but I am not sure. The 4wd light isn't jumping back and forth, but I don't know what else it could be. Any thoughts would be appreciated. This is on a 2002 650 prairie. Thanks in advance.

 

Is it just one time clunk or continuously clunking? Set the bike on a stand with the wheels are in the air. With engine off, rotate one of the front wheels in one direction and see which direction the other front wheel rotates - should be opposite. If not, your diff gears are shot.
There is set of dog gears at the end of input drive shaft just inside the front diff gear case (toward the back). See if dog gears are all rounded and worn out. The 2/4WD light would not "normally" flash if there is a mechanical failure. The sysem detects electrical failures by measuring the resistance and voltage from the nodes.

 

If you are in low range it could be a gear adjustment but it would be very loud clicking noise.

 

If you jack up my p650 and spin a front tire in 2wd the tires do not spin opposite. I dont think any p650 will rotate those tires like a car diff, they will slowly drag the same direction due to the front diff working like a clutch. Dealer confirmed what Im saying.

Id be curious if other p650s and p700s rotated opposite?

I did have a clunking noise, it was the shifter, id head into that first as its pretty common.

 

Yes, two front wheels of P650/700 and BF750 may rotate in the same direction in some cases. The design is same on all those models and they share all the same components in the diff gear box. When two front wheels rotate in the same direction, you can assume there is no problem in the spider gears IF AND ONLY IF you can "hold" one wheel stationary and continue to rotate the other wheel. The reason for rotating in the same direction is due to the drag mainly caused by the viscosity of the oil (and somewhat due to increased friction between mating surfaces of bevel gears and the center shaft - beginning of seizure). Normally, they would roate in opposite directions when turning one wheel by hand in the air with no adverse drag in the diff gears. If you can't hold one wheel - no more differentiation, your diff is shot. When draining the diff gear oil if you see any shiny metal particles, another sign of wear/seizure. There is a way to avoid the diff gear seizure. BTW, becareful not to strip the drain bolt (allen head). It is damn tight.

 

Yep thats right. If you cant hold it you got problems, but they wont rotate opposite. This is the same reason if you have a motorcycle on a stand and the rear wheel starts spinning in neutral. There is oil and drag.

If you dont have 2 people put it in 4wd and use your foot to stop a front in the mud/snow.

What do you mean with this sentance.
"There is a way to avoid the diff gear seizure"

I noticed last fluid change mine had some shiny flakes in the oil. But I think its just the clutch plates wearing a bit. I ran a magnet though the fluid and couldnt pick up any pieces.

 

Thanks for all the info guys. I'm going try some of that tonight. Hyashi, it is just a one time clunk, and then it goes away for a while. Only comes back when you load it up agian, or drive up another hill. I have a hard time believing there is to much wear on the gears because the oil looked pretty good when I cahnged it 100 miles ago, except for having some water in there. Hoping for the shifter to be the cause, but would that being out of adjustment cause a loud clunk intermittently? I'll dig into this weekend if I can't find the problem tonight, and let everyone know what I find.

 

Mine clunked one in a while under hard throttle, was the shifter, wasnt going into low deepenough.

 

Just thought I'd let all of you know that it was the shifter. Thanks for all your help.