So here goes, I have just fixed an RGM belt primary to my ‘74 850, yesterday I took it for a ride to test the belt tension and confirm everything was ok, I had previously run the bike with the primary cover off to check alignment and whilst out yesterday day I stopped a couple of times to check the belt tension when the bike was at fully operating temperature, all was well there is no tension on the belt when it’s hot and it still has over 1/2" of free play.
Now to my problem, I had covered around 150 miles in Wales on a mixture of roads from single trackers, hilly minor roads and a few main roads all with the aim of making the bike work to generate heat and test the belt tension. I stopped for a late breakfast in Rhayader, vey goos it was too, then fired the bike up for the 110 mile run home feeling very pleased with myself that all was well. Anyway all was not well, under moderate load I was getting a really heavy vibration through the foot pegs this was present in all gears so I stopped at Crossgates, whipped the primary cover off and had a look assuming it must be to do with the recent work. What I found was that the belt was still at the correct tension, there was no evidence of the belt tracking either in or out and no marks on the outer edge of the belt (I’ve stripped it this morning and can now verify that there are no marks on the inner edge of the belt either.) My assumption while sat at the side of the road was that either the clutch centre nut had come loose or the retaining circling had failed or deflected but obviously couldn’t get to this as I didn’t have my diaphragm spring tool with me. I came to this conclusion as I could feel a very small amount of play in the clutch basket. I called aa pal who picked my trailer up and made the 200+ mile round trip to collect me. Thanks Rog, you are a star.
We move on to this morning and the strip down. I took the primary cover off and as with yesterday all was well, the tab washer was still in place and the play I could feel yesterday has all but disappeared probably due to the change in temperature. I had torqued the centre nut to 50 ft lbs, less that the 70 ft lbs in the workshop manual which is generally considered to be too much. I undid the centre nut which was snug but certainly nowhere near the 50 ft lbs I’d tightened it to, I removed the clutch basket and centre checked the location of the circlips (bearing and clutch centre) and checked the bearing which is perfect. The clutch retaining circling on the main shaft looks ok but obviously will be replaced when I reassemble. In addition to this I have checked:
1. Checked gearbox mountings top and bottom - all good there
2. Checked for play in the main shaft - all good there (the gearbox was rebuilt about 5,000 miles ago by Norman White before I acquired the bike)
3. Gearbox oil level - all good
4. Belt alignment - all good there as also indicated by the belt
5. Wheel bearings - all good there
6. Engine mounts including those to the gearbox plates
7. The spacer behind the clutch that encapsulates the main shaft circlip was where it should be
One thing that I noticed today was that the drive chain was a bit loose, I has to replace this when I fitted the belt drive as the existing chain was too short, the slack is just the chain bedding in but I’m wondering if a bit of chain slap might have created the heavy footpeg vibrations? (I am not going to adjust the chain until I have reassembled the primary and tested it otherwise I’m not going to know where the issue was assuming it disappears).
What I intend to do is reassemble the clutch with a new circlip, torque if up, leave it for 24 hours and re-torque it, I’m not sure if this will achieve any thing but it will allow any deflection in the circlip to be identified (if there is any movement to achieve the same torque), test ride and see if the vibes have gone, if not I’ll adjust the chain and test ride again.
So my questions are;
Do yo think I’m on the right track?
Is there anything else I need to check?
Is 50 ft lbs too little or too much torque on the clutch centre nut?
Any other ideas?
I’ll order some circlips today and they’ll be with me on Tuesday so I’ll be back into it on Tuesday evening.
Edit - Just to add after posting I had another thought and have just checked the drive chain for tight spots or bad links and it’s fine.
Dave
I’ve not used the RAC before, it comes with my bike insurance, I also have Green Flag and that comes with my bank account so maybe they might be worth a try if I need help in the future. 
