Worrying transmission noise..

Previously K Glassborow wrote:

I have run a Norvil belt drive for many years now and learned early on to take Les Emery's advice for once!! Top of belt run to locating boss 30mm. I squeeze a socket in there to check. It will seem loose when COLD but anything like cambelt tension will lead to difficult gear changing and a horrible transmission feel once everything heats up. That clutch drum grows quite a bit. It does depend on the BD parts but with typical designs in aluminum the belts tighten quite a bit HOT.

Thanks for this - I'll certainly have a look at the belt tomorrow morning. However, my problem seems to get slightly better as the bike warms up and although I'm a novice when it comes to interpreting 'Norton noises', the sound oscillates between clunking and grinding, as thogh the chain is very slack (which it isn't) and snatching, or the chain is scaping along the chain guard.

I must get out and do more listening but it's difficult to hear where the noise is coming from and adoptiing an 'apache leaning over the side of the horse' riding attitude does little to inspire confidence in other road users... Hugh

Previously K Glassborow wrote:

Hugh

Try to run it on the centre stand in neutral and in the gears. With the primary off and no load it will sound clattery when so close to it but it might help you spot any unusual noises. Rev it up out of gear so you can eliminate the chain as a source. Certainly unusual that it improves with running and heat. Clearance on the rotor and stator OK? Would probably be worse at speed if there was an issue. Best of luck and let us know if you find anything. Is there no-one near you who can help?

Hi - Thanks again for coming to my rescue. I have run it up out of gear and the is no noise, it is only when the drive train is under 'plus and minus' load that it becomes obvious. I had thought of the rotor/stator being the problem and will try your excellent idea of running on the centre stand with the chain (belt) cover off; I should be able to apply some load by using the rear brake.

Will certainly let you know how I get on. Help much appreciated! Hugh

Thanks both - I always check the back wheel clearance before running the bike on the stand - the idea of doing an Evel Knievel tribute act through 2 cars and a workbench doesn't appeal!

I'll check the engine bolts as advised - I've already checked the gearbox top and bottom studs. Presumably the relationship between the rotor and stator is set by tightening bolts that go through the back of the primary chainchase into the crankcase - but I guess if the engine could wobble in the cradle, these bolts wouldn't hold?

Thanks again - excellent forum support! Hugh

Previously david_evans wrote:

Hi Hugh, the stator studs only go into the inner half of the primary chaincase. There are 3 further screws that attach the inner chaincase to the crankcase. (4 on electric start models I believe.) and the inner chaincase sits on a close fitting register so no movement there. The relationship between rotor and stator is not adjustable apart from what movement you can get on the stator studs as you tighten it up. I have opened up the holes in the stator to achieve a better adjustment but drilling just a few thou bigger than the existing holes is tricky without a proper drilling machine.

Might be worth getting a proper workshop manual and parts list if you don't already have one.

David - thanks for all this, and good idea to get a proper workshop manual; so far I have survived on the instruction book and a parts list. Help much appreciated, Hugh.