f650 sproket

**JLawton** · #1 7 Feb 2006

Morning chaps,

How much 'play' or lateral movement should there be on a front sproket. With the chain off and a finger and thumb at the top and bottom of the sproket, it moves from side to side around the drive shaft more than i thought it should have. is this normal? also its a 1996 funduro and is not held on buy a nut, but some other method. anyone know how to lossen this device so i can change the sproket if need be. Both chain and sproket are realtively new.

Tally ho,

**quastdog** · #2 8 Feb 2006

Try the Chaingang for anything 650 related.

http://f650.com/website/

But - search the FAQ's first. Don't even think of asking without searching either the FAQ's or their forum first. If you can't find an answer, then they'll be more than willing to help.

**Bossies** · #3 8 Feb 2006

The Funduro front sprocket is held in place with an exterior circlip (Looks like a ring/washer with a section cut out). Proper way to remove it is with External circlip plyers. Otherwise very very carefully with two screwdrivers but make sure not to bend it.

There is a little bit of play on the sprocket but the circpli should stop it from moving in and out. Just have a close look at the "teeth" on the drive shaft coming out of the engine. If their edges are still sharp then ok.

**lecap** · #4 22 Mar 2006

Be very careful with the drive chain sprocket on said early Funduro model. BMW changed the drive sprocket mounting to a central nut very soon and not without good reason. If your sprocket or drive shaft is badly worn (or both) the movement of the sprocket under changing load can lever the circlip out of its groove. The sprocket will then come off and you might end up with a spectacular wipe out (in my case): The chain seized between swingarm and rear sprocket and locked the rear wheel. Travelling at some 60 to 70 km/h on Dock Road in CT I left a 30m skidmark but somehow managed to stay on top and stop on the emergency lane.
BMW recommends to replace the circlip with a new one when replacing the sprocket. In any case be very careful not to overstretch it. Rather get a cheap circlip plier than using makeshift tools. Replace the sprocket if it's badly worn. It should move freely on the shaft but it should not have a lot of play. Ask a trustworthy mechanic if in doubt.
If you have any major work to do on the engine get a gearbox main shaft from the later Funduro and throw yours away.

**Nigel Marx** · #5 23 Mar 2006

Also, make sure you note which way around the sprocket is before it comes off. There is a lip, which makes the teeth slightly off-set, and if it goes back the wrong way, the chain will throw off, as soon as it get a little slack. Don't ask me how I know......
Regards
Nigel in NZ

**JLawton** · #6 23 Mar 2006

Thanks chaps,

I'm putting a new sprocket on at the weekend. There seems to be a general concensus that the circlip method of holding on the front sprocket was poor. Even BMW upgraded to a nut for the 1997 funduro onwards. I gather it is important to ensure the correct circlip is used to stop the sprocket falling off along with the 'o'ring placed behind the sprocket to push it out a place a bit more pressure on the circlip.

I think the play on mine is due to a worn 'O' ring ( if one has been put there at all ) or circlip. Anyway, its all coming off this weekend so I shall see if my drive shaft is worn and buggered and any other damage that may have occured.

Just as a warning, during my research I have come across several stories of riders falling off due to the front sprocket falling off the bike because the circlip dissolved or pinged off. If you have a pre '97 funduro might be worth checking it.

thanks folks

**lecap** · #7 24 Mar 2006

Not too likely that you will find any damage on the shaft. It's a lot harder than the sprocket due to its thermal treatment. You sometimes get damage on the shaft but that's afer using cheap ill fitting sprockets on dirt bikes for a long time (sand, dust and lube grind in the gap between shaft and sprocket).
After the first circlip pinging off and me almost seeing my a*** I kept a close eye on the circlips and did not have further problems until the company sold the bikes.