Walterg

Thanks. Mine is indeed vented and I know it's open because it let's water in.

15 years later..... What do you guys mean with "Burping" the bevel drive?

Well. I'm leaving things as they are now. No more weird sounds and the bike rides wonderfull. I'll fitt the new speedometer cable that arrived today and while I am at it find out why the tachometer was jumping up and down all the time. So time for some electronics.

Yes indeed. With mine it sounds very clunky though.

Wow!! Thanks for explaining Pete. Love the bit of history too! It's completely clear now. By the looks of the diagonal and rounded faces on parts #15 and #16 sudden rotational changes direct the energy into the spring washers which will compress and store the energy. When the rotational force lets off again the stored energy is released back to the drive shaft. I have to admit I love this stuff!

By the looks of it part 15 is made out of rubber and sits between parts 13 and 17 to take the impact of sudden radial loads. The discs (parts 18) form a Belleville spring and catch the axial movements caused by the rear wheel going up and down and thus pushing the drive shaft into the gearbox. Right?

Can somebody explain what this does? I think it is supposed to 'dampen' shocks coming from the rear wheel.

The rattle disappeared after I screwed the gearbox back in the bike again the first time. Since I messed up he clutch the first time I had to take the gearbox off again. After putting everything back together again the second time the rattle is still gone but the clunking sound you hear when you push the bike back and forth and change direction from forwards to backwards (again with the bike in gear and my hand pulling the clutch lever in) seems louder. The bike rides lovely though. During the ride I don't perceive any weird sounds or unwanted movement in the drivetrain. Changing gears is fine like it has always been. Indeed I now understand that this and this should be in the same picture.

Thanks for the picture Docc. So far I haven't been able to find anything on how the wormwheel bushing in the gearbox that drives the spindle sits on the shaft. I unscrewed the speedo cable and found that it was just broken. Again no indication as to what is causing those sounds. I rode 120km today and I rode the bike pretty hard but no indication that anything is wrong with the gearbox.

I fixed the slipping clutch. The cause was a big blob of grease that I somehow managed to get on the clutch plates and did not notice during assembly. I also fitted the rubber O-seal on the drive shaft. After I checked the gearbox a while back I have been riding the bike a few times now (about 300 km) and I did not come across any issues indicating there is a problem with the drive train / gearbox. This morning though my speedometer stopped working. The cable 'looks' fine but I will check it when I get home tonight. The idea that the issue is with the shaft that extends from the final drive shaft into the gearbox (Gearbox outgoing) is growing. Although at this moment I can't find any picture or drawing which shows which part drives the speedometer transmission. I have a one week holiday planned with the bike starting the 29th of August. I hope it will be clear and fixed by then.

Yeah. I'll fix that this week when I have a look at the clutch.

Yes. That one.

Still some more work to do: While cleaning up my workbench I found the rubber driveshaft seal ring on my workbench Under high load (shifting back one or two gears and giving a lots of throttle) the clutch is slipping which I never had before I took everything apart. I'm sure the clutch assembly is fine. I'll do a search to see what I can find on this.

Yesterday I finished putting the bike back together again and now the rattle is gone! After having made two test rides I was not able to reproduce the rattle. Pushing the bike makes no sound at all. I'm still puzzled as to what it may have been but I had a close look at many parts and everything looked and felt good. Let's see if it stays this way. At the moment I'm just very happy I can ride again! When assembling the bike and because the motor was still in the frame I had to mount the clutch in a vertical position. To keep the springs in place while screwing on the clutch disk I wedged some electric wire between the spring coils then pushed the disk against the flywheel while holding the wire taut and then pulled out the wire through the center hole. I was amazed about how well this worked This is the PVC centering tool that I made. Worked perfect the first time! The PVC end-cap that I bought in the DIY shop had the perfect measurements. I glued some extra pieces on it to align the two clutch discs. May thanks for all your great comments and suggestions. I'm all happy now! By the way: The clutch plates thickness was at 57% so I reused them. The oil was coming from two bolts so I tightened them a bit.

The bike has to move so I'm putting everything together again. After that I'll figure out what to do next. Grazy that I coudn't find anything. I hope it's not in the drive shaft damper (15 - 18) which I can't see unless I take the shaft out. Which I didn't.

I don't have a picture now but the peg is still engaged and looks fine. Not bend or anything.

The driveshaft alignment is fine. I marked the shaft halves with white paint years ago to prevent any alignment issues. While the gearbox was out I held the gear that engages with the clutch assembly with my hand to simulate clutch load on the gearbox while rotating the drive shaft with my other hand with the gearbox in neutral and in different gears. No rattle. I opened the rear gearbox cover and the gears look and feel fine. All the pegs that secure the nuts are in place. Except for the gear that's on the drive shaft axle, I found no play. Picture of peg 1 Picture of peg 2 Picture of peg 3 Video that shows play.

Thanks for all the great reactions. With your help I'm sure I will get everything sorted. At first I thought that the oil that was leaking through the seal was swung upwards to the left by the rotation of clutch. Then I thought that one or two of those bolts were leaking but they seem to be torqued down ok. I did not arrive at the idea that the vent could be leaking. I will check that tonight. The thickness of the plates looks ok but after 85K kilometers they are a little thin indeed. I intent to replace them together with the 10 springs. Good observation about the 10th spring Scud. It rolled away just before I took the picture. The input hub retention nut looks ok to me. It also did not feel lose when I tried to hold it with my hand while rotating the drive shaft with a gear selected but I will definitely double-check it. I still need to check the gears and nuts that are behind the rear gearbox cover. One of the cover bolts broke off while trying to get it off so I decided to focus on the clutch first.

I removed the clutch assembly and everything looks fine to me. The blue colouring of the plates is the reflection of the wonderfull blue sky we have at the moment. The first repair task that I came across so far is replacing the leaking crankshaft seal. Here are some pictures of the clutch parts. Clutch parts I Clutch parts II Leaking seal And my workplace here

Rolling the bike in neutral with or without the clutch lever pulled in makes no sound at all. Rotating with and without the gearbox cover makes no sounds. Just the normal silent sound of rotating gears. @Pete and Pressureangle: Just to be clear: With drive shaft you mean the shaft with the universal joints that goes from the gearbox to the rear wheel? I'm asking because I don't see any pegs. Just two bolts per universal joint. I just made a simple clutch plate allignment tool so will continue with the disassembly.

Thanks Pressureangle. The video show a few good points to keep in mind.

I took the gearbox of the bike and tried to reproduce the sound by turning the drive shaft and changing gears. Nothing....No rattle or clunking or any other disconcerning sounds. Just that light whizzing sound of gears turning smoothly. I tried several gears with and without trying to simulate some load on the primary gearshaft by holding the gear that "interacts" (Don't know the correct word for that) with the clutch but all sounds great. Anything I can try at this point? I'm thinking now that maybe the clutch mechanism is making that allthough I wouldn't know how....I'm still trying to figure out how to remove the clutch assembly. Clutch picture. Picture of the gear that engages with the clutch. View inside the gearbox. Picture of my test setup.

Yeah Weegie. Now that I have reassembled the bike and was able to reproduce that sound again, I changed my opinion about what's causing the rattle and I don't think it's the clutch. The sound is not that "Metal plate jingling" kind of sound. It's more like gears just touching each outher when turned. My answers to Scud's questions: The rattle when pushing is only when the bike is in gear, and clutch lever pulled in. Answer>> Yes, that's correct. Is it safe to assume that the noise is absent when pushing the bike in neutral (whether clutch is activated or not)? Answer>> Yes. No sound whatsoever. Have you tested different gears? Does the noise speed up or slow down as you change gears? Answer>> Interesting. The sound is different per gear. In first gear the rattle is the loudest and has the highest frequenty (RPM). Going up the gears seems to make the rattle a bit quieter per gear. Do you have a way to lift the rear wheel? If so, you can bind the clutch lever in (zip-tie or bungee), then rotate the wheel while changing gears and listen for noises. Answer>> Besides making a few steps back and forth with the bike everytime I also lifted the rear wheel for testing. With the wheel up, it will also be easier to look for play in the driveshaft. Answer>> The drive shaft is fine. No play in any direction (I love lubing that thing ) and the bearing through which the splined shaft exits the gear box has no play at all. There's also no play on the splined shaft itself in any direction. Note: When I turn the drive shaft (the rear wheel) and change direction there is always a few degrees of play at first but I think that's normal as the gears change direction and change sides on the gear tooth. It looks like I will be draining and opening up the gearsbox soon again.

Sorry but I'm still/again having some doubts about whether I can ride my bike without making things worse so I made a 10 second video. The reflection on the painted wall shows what I'm doing and you may have to turn up the volume when you play it. Transmission rattle video with sound

Thanks guys. I finally had some time to dig into this issue and I started taking parts off and now I'm quit convinced it indeed has to do with the clutch. I never roll the bike with any of the gears engaged and the clutchlever pulled in simply because it's heavier and less easy to do. This time it just happened to be so and I heard the noice for the first time. The driveshaft looks fine. No play in any direction. It's also not making any noise. Took the side panel of the transmission off and everything looks and feels as it should. Also no play on any bearings. At this point I could cleary hear the sound coming from the rear side of the engine but as the crankshaft is not turning it has to be the clutch! Reading some of your comments about the noisy clutch I'm starting to think I am being worried about a problem that does not exist. So now i'm thinking that I just assemble my bike again, put in new transmission oil, do something about rainwater getting into the gearbox ventilation and go riding. On a side note: I must have moved my bike this way before in the past but I don't recall hearing any of this noise. It's allways the brakepads that make most of the noise. Could it be that the clutch is wearing out and that that's the reason it's making more of that metallic sound?