2003 BMW F650CS - Difficulty selecting 4th and 5th gears gear - sorted ! Please read

costellon

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Howdy.

I purchased a 2003 F650CS a while back with gearbox problems. Most of the time I couldn't select any gears higher than third but occasionally it would go into 4th gear whilst being driven hard.
I stripped it expecting to find a dodgy selector only to find that the problem was caused by the neutral light switch plunger CATCHING the damaged plastic washer on the bottom of the selector drum that acts as an insulator for the neutral light circuit.
The plunger was limiting the movement of the selector drum.
See photo below, damaged washer on left, good one on right.



On closer inspection I found that the damage to the washer must have been caused by a sharp edge on the tip of the neutral switch that etched away at the plastic - Badly installed replacement switch perhaps ? Stuck plunger at some stage ? Any ideas ?
Photo below.



So, why am I posting this ? To give others that may have the same problem a heads up. If I would have been happy to live without a neutral light I could have simply removed the switch, blanked off the hole and then have been able to select all gears and use the bike as normal - had I been aware of where the problem lay.

If you are suffering from this problem and you want to check, simply remove the neutral light switch, lift the rear of the bike off the ground, get a mate to spin the back wheel (engine not running) and go through the gears whilst you look through the hole that's normally occupied by the switch (using a penlight) ... if the plastic washer/ insulator is damaged you'll see it as your buddy goes up and down through the gears and can then decide if you'd rather a complete engine removal, stripdown and rebuild or living without a neutral light.

Alternatively, you could unscrew the switch itself by about 5mm, take the bike for a drive and see if the problem has sorted itself ...

I spent days searching the net for posts by people that had experienced a similar problem and was fully expecting to find something like a worn selector fork as being the culprit - but I didn't expect it to be such an odd and simple fault. You live and learn ... and share.

Additionally, having had a few of these CS's, replacing the output shaft bearings is a matter of course when splitting the crankcases due to the amount of cowboys that don't follow the correct procedure when tensioning the drive belt and thus knacker the bearings by putting too much load on the front belt pulley by having the belt too tight. Mine is a low mileage engine and already the pulley side bearing feels notchy.

That's my contribution.

Thanks.
 
Interesting - one for the knowledge bank. Many thanks for posting.
 
Very similar to the problem which brought Gaz's XC to a premature halt ....... in New Mexico :D
 


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