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Discussion Starter · #1 ·
The countershaft on the older (pre97) model bikes only has a circlip to hold the front sprocket on.
There have been many reports of the front sprocket coming off these bikes.
There are a few causes.
Wear on the circlip groove
Worn circlip
Wear on the shaft.
The previous owner of my bike had the front sprocket come off as he stopped at a traffic light.
It could cause a very dangerous situation of the sprocket were to come off at speed.
The later bikes and the GS 650 bikes all have a modified countershaft with a nut and tab washer on them to overcome the problem of the circlip.

I found the circlip groove on the countershaft was worn on my bike so decided to modify the shaft to have a nut and washer like the later bikes.
The first step was to remove the sprocket cover and sprocket.
I then sharpened some Tungsten tip drills and drilled the countershaft .
First was a small hole about 4mm diameter, then a 6mm diameter then up to an 8mm until I got to a 10mm drill size.
I used a 12mm tap to tap a thread in the shaft.
This has to be done very slowly as it is very easy to break a tap in a hardened shaft.
First use a tapered tap, then an intermediate then a plug tap to get the thread to the bottom of the hole.
I then got a High Tensile bolt and cut the threaded section off and ground the end until it was the same shape
as the end of the drill.
I used loctite and threaded the new bolt into the countershaft.
I decided to keep the circlip as a double safety measure so machined a washer from an old nut that fitted over the circlip ( just so that the circlip could not come undone).
Then reinstalled the sprocket , circlip, put the washer on and did the nut up.
This was 4 years ago now and I have had no problems at all.
I also make a steel sprocket cover with a section in it that has a nylon insert that prevents the sprocket coming off and also protects the crankcase should the chain ever break.
I did have a stick go between the chain and sprocket once that caused the chain to chain to jump off the rear sprocket.
It takes a while to do the mod but it is well worth it for those who have circlips only holding the front sprocket on.
If it is possible to get Carbide taps they would be better for this job as they are capable of tapping threads into hard steel much easier.
Cheers
Pete
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The countershaft on the older (pre97) model bikes only has a circlip to hold the front sprocket on.
There have been many reports of the front sprocket coming off these bikes.
There are a few causes.
Wear on the circlip groove
Worn circlip
Wear on the shaft.
The previous owner of my bike had the front sprocket come off as he stopped at a traffic light.
It could cause a very dangerous situation of the sprocket were to come off at speed.
The later bikes and the GS 650 bikes all have a modified countershaft with a nut and tab washer on them to overcome the problem of the circlip.

I found the circlip groove on the countershaft was worn on my bike so decided to modify the shaft to have a nut and washer like the later bikes.
The first step was to remove the sprocket cover and sprocket.
I then sharpened some Tungsten tip drills and drilled the countershaft .
First was a small hole about 4mm diameter, then a 6mm diameter then up to an 8mm until I got to a 10mm drill size.
I used a 12mm tap to tap a thread in the shaft.
This has to be done very slowly as it is very easy to break a tap in a hardened shaft.
First use a tapered tap, then an intermediate then a plug tap to get the thread to the bottom of the hole.
I then got a High Tensile bolt and cut the threaded section off and ground the end until it was the same shape
as the end of the drill.
I used loctite and threaded the new bolt into the countershaft.
I decided to keep the circlip as a double safety measure so machined a washer from an old nut that fitted over the circlip ( just so that the circlip could not come undone).
Then reinstalled the sprocket , circlip, put the washer on and did the nut up.
This was 4 years ago now and I have had no problems at all.
I also make a steel sprocket cover with a section in it that has a nylon insert that prevents the sprocket coming off and also protects the crankcase should the chain ever break.
I did have a stick go between the chain and sprocket once that caused the chain to chain to jump off the rear sprocket.
It takes a while to do the mod but it is well worth it for those who have circlips only holding the front sprocket on.
If it is possible to get Carbide taps they would be better for this job as they are capable of tapping threads into hard steel much easier.
Cheers
Pete
View attachment 38405 View attachment 38406 View attachment 38407 View attachment 38408 View attachment 38409
The countershaft on the older (pre97) model bikes only has a circlip to hold the front sprocket on.
There have been many reports of the front sprocket coming off these bikes.
There are a few causes.
Wear on the circlip groove
Worn circlip
Wear on the shaft.
The previous owner of my bike had the front sprocket come off as he stopped at a traffic light.
It could cause a very dangerous situation of the sprocket were to come off at speed.
The later bikes and the GS 650 bikes all have a modified countershaft with a nut and tab washer on them to overcome the problem of the circlip.

I found the circlip groove on the countershaft was worn on my bike so decided to modify the shaft to have a nut and washer like the later bikes.
The first step was to remove the sprocket cover and sprocket.
I then sharpened some Tungsten tip drills and drilled the countershaft .
First was a small hole about 4mm diameter, then a 6mm diameter then up to an 8mm until I got to a 10mm drill size.
I used a 12mm tap to tap a thread in the shaft.
This has to be done very slowly as it is very easy to break a tap in a hardened shaft.
First use a tapered tap, then an intermediate then a plug tap to get the thread to the bottom of the hole.
I then got a High Tensile bolt and cut the threaded section off and ground the end until it was the same shape
as the end of the drill.
I used loctite and threaded the new bolt into the countershaft.
I decided to keep the circlip as a double safety measure so machined a washer from an old nut that fitted over the circlip ( just so that the circlip could not come undone).
Then reinstalled the sprocket , circlip, put the washer on and did the nut up.
This was 4 years ago now and I have had no problems at all.
I also make a steel sprocket cover with a section in it that has a nylon insert that prevents the sprocket coming off and also protects the crankcase should the chain ever break.
I did have a stick go between the chain and sprocket once that caused the chain to chain to jump off the rear sprocket.
It takes a while to do the mod but it is well worth it for those who have circlips only holding the front sprocket on.
If it is possible to get Carbide taps they would be better for this job as they are capable of tapping threads into hard steel much easier.
Cheers
Pete
View attachment 38405 View attachment 38406 View attachment 38407 View attachment 38408 View attachment 38409
Great job Pete ! Fortunately mine already has the upgraded nut package. What ever happened to the other F-650 forum????
 

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Discussion Starter · #3 ·
The other forum, changed servers and they are having heaps of trouble getting it to work. It was briefly there 2 days ago but not possible to log in due to database errors, so it looks like it may be fixable sometime.
You are lucky that someone already changed the countershaft on your bike, I think BMW realised the error of their ways in 97 and changed the countershaft arrangement then.
Pete
 

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The other forum, changed servers and they are having heaps of trouble getting it to work. It was briefly there 2 days ago but not possible to log in due to database errors, so it looks like it may be fixable sometime.
You are lucky that someone already changed the countershaft on your bike, I think BMW realized the error of their ways in 97 and changed the countershaft arrangement then.
Pete
My bike is a 97 so it was changed at the factory. I've spent all winter cleaning and upgrading the bike. In fact it's hard to tell it from a brand new bike right now. The weather is getting slowly better now so been doing some riding. Glad I found you here because I have always enjoyed your posts and the helpful info I get from that. Hopefully, they will finally get the other forum going.
 
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