Hi,

Bmw k100rs 1986ish 102k miles. Owned for 12 yrs.

I changed the oil today and found what looks like - single output shaft rivet attached to the magnetic drain plug. I didnt have a filter so haven’t pulled that.

Bike runs fine with no significant Noises. I changed oil and filter 6 mths (7k) ago and have always done my own changes with no evidence of rivets.

The is a wealth of knowledge on the site to change out the output shaft which is great.

My question is  : Is it a safe failure when it does go? 

Life is busy and this my daily and would like to postpone until I have time and space todo it myself.

Comments appreciated

Cheers Duncan

I have heard of a couple that have failed and just lost drive but if it were mine I would certainly be finding a 12 rivet shaft and making plans to do the job in the very near future.

ddunks wrote:

My question is  : Is it a safe failure when it does go? 

It's safe. Spose you're on a trip and all rivets suddenly fail, the crankshaft still turns and the engine output shaft just comes to a stop, you're walking. Probably not even that bad nowadays since you probably have a mobile phone to get a lift.

If you remove the crank cover, you can see how many rivets are missing and if the holes are worn and elongated, and how much slop there is.

Look for the parts you will need or a whole brick. My last brick cost $300 as it was a neglected no-go bike, just wanted it as a parts bike.

dont forget , when you have no drive , there is no oil pump or coolant operation .

just a heads up

Did you or a prior owner install a magnetic oil drain plug? The factory one is aluminum which generally isn't very magnetic.

charlie99 wrote:dont forget , when you have no drive , there is no oil pump or coolant operation .

just a heads up

I never thought about that. Does oil pump drive also come from the output shaft? Good to know this.

Yes it was a magnetic drain plug I’d put on a few years ago. Worth the purchase if it flags little nuggets like this. Thanks for comments, it’s running nice at the moment so hopefully I have a bit of time to formulate a plan. I may even consider getting someone to do the work for me and if so maybe a good engine swap may be the cheapest and easiest solution. I have no space or time at the mo and already have another bike parked up waiting for me to get to it. Cheers Duncan

Would you say your brick has a little bit of a rattle sound, or might there be a bit of a clunck after the engine comes to a stop? These might not be noticeable if it's been doing it for years. 

What's the diameter of the rivet?

Since you say it's running nice with no significant noises, I'll add some wishful thinking idea's. Maybe it's not an output shaft rivet. Maybe it's only one output shaft rivet that wasn't installed well. Maybe somehow an extra rivet got in there. I know this is unlikely but wouldn't it be good if you looked and found six rivets, and there's nothing wrong with your brick, or the diameter of the rivet tells us that it's not an output shaft rivet.

Oh I do like a bit of positive thought. There may be might be a slight rattle from the timing change but not significant I think most people wouldn’t be able to hear it. No clunks either but I will hop on tomorrow and see to be sure as I do ride with ear plugs a lot will take the cover off and look this week and count rivets. The rivet looks like it has had a hard life. But head looks identical to output shaft visible rivets. 6mm dia 14mm long. Cheers

The top looks a bit different to mine, but unfortunately that does look like a flogged out rivet from the output shaft.

charlie99 wrote:dont forget , when you have no drive , there is no oil pump or coolant operation .

just a heads up

Hi Charlie,

I was just pondering re this. Totally understand the dangers of no oil or coolant pump operation. But the penny just dropped! After failure does the drive still continue to the rear wheel? I had assumed id quickly know when it goes bang because of a lack of drive and therefore I would have no reason to run the engine further therefore causing damage due to no coolant or oil circulation. But am I correct in thinking that after failure of rivets the drive will continue and the main obvious symptoms would be unpleasant engine knocks /rattles with secondary symptoms being (less obvious) no pump operation! Ie I could naker engine due

The 6 rivets are your drive to the rear wheel. If they go the bike comes to a stop and thats it.

Economics are such that an engine swap is more likely to be the cheaper option.

Update: 10k later and still running on 5 rivets. Still on the todo list and now have a collection of parts todo the job but no unpleasant noises as of yet. I do visual check every few mths removing the crank case cover and am more diligent with the oil changes.

Hi Dunc,

I remember this thread. I've just read it again and I'm surprised that I mentioned a few scenarios, but not the main one I was thinking of. Let's say the previous owner replaced the output shaft a year before you bought it, and a few old rivets were still in the sump.

You may have counted five rivets, or even six rivets, but have you actually seen a hole where a rivet should be? Is it a six rivet output shaft or a 12 rivet one? A photo will probably show which one it is. If there is a hole, can you post a photo so we can see the amount of wear?

I’ve had the bike for 75k and now at 112k miles so doubt the previous owner had done it. I can see what looks like a countersink where the rivet was, it didn’t look particularly fudged. I will take a look again at the next oil change which is imminent. But may have a photo already I’ll look but from memory it’s hard to see in the photo. I am a glutton for punishment despite a lack of time and space I picked up a 12 rivet shaft for £30 which included a bearing ( which had slight play) Now you’ve reminded me. I can only source a 80mm bearing for this shaft with circlip but think I need one with a flange. I have therefore sourced a circlip same id diameter but with a smaller od diameter to match flange size. I was going to get a spacer ring to sit behind the circlip to emulate the flange on the unavailable bearing. Am I over thinking this ? Are the bearings interchangable?

You can see the hole in these 3 pics not so clear however.

You've got onto this at an early stage, bonus.

I think the rivets are deliberately softer so that they wear out first. One option, if the holes are still good, go to a bearing place and get a few more than six rivets, and the tool to install them.

Another option. The bearing in your brick could still be good, although it might get damaged when removing with a puller. I removed the bearing with two long screwdrivers cause I didn't have a puller small enough. Less pressure but took ages to come off. The sensible part of my brain said "daveson, this is ridiculous wishful thinking, It's not moving, you're wasting your time" The stubborn part of my brain said "get stuffed, I've wasted a few minutes and I'll waste a few more minutes too"