Those of us with early cars will probably have wondered what odd things go on at the rear sprocket - the one with no flange on the outside edge and the belt overhanging that edge by a short distance. Having done the alignment of the rear spindle by spinning the wheel back and forwards between adjustments till the belt didn't seem to wander further on to or off the sprocket I thought I'd try to find out what was going on under full load both on power and over-run so I stuck a GoPro and a light under the boot to find out and the results are here;
The conclusion from this would appear to be that nothing much is going on! Oh well, apart from the straight bit of road that I did the camera runs on it was a good run in the sunshine.
fascinating: I really do wonder why there is no flange on the side of the pulley next to the suspension unit.
Looking at photos on the web all the HD rear pulleys have closed sides.
Another thought: does the M3W have a proper "cush drive" built into the pulley?
Every bike I've ever owned has had a cush drive (blocks of rubber) between the drive and the wheel, they aew normally built into the sprocket carrier. But looking at you video I wondered...
Peter
Last edited by Peter J; 30/03/1505:27 PM. Reason: Additional text
Peter, 66, 2016 Porsche Boxster S No longer driving Tarka, the 2014 Plus 8...
On the early cars like mine if the rear sprocket was simply spaced over a bit so that the centre lines of the two sprockets were aligned allowing an outer flange to be fitted, then I think it would foul on the swingarm but I haven't tried to find out. I do recall a post a while back where someone had got their one converted to the later spec, two flange rear sprocket at some considerable expense. Sounded like a lot of parts had to be changed. I'm pretty sure there is no cush drive at the back - presumably the belt is supposed to have a bit more give in it than a chain (though I have my doubts) and the compensator should play it's part as well in damping out shock loadings. Use to wrap the rubber blocks in bits cut out of inner tubes to get the slop out of the cush drive on my race CBR600 - worked beautifully.
My first sprocket had only one flange on it. It wore out in about 3,000 miles. The second one had a flange and it lasted about 9,000 miles before eating itself. The third one has a flange but its days are numbered. I sent the second one to SuperMax where the aluminum teeth were machined off and relined with a neoprene set with only one flange.
If the tracking and tension are done right having two flanges should not be necessary. The bevel box has two so it won't drift too far.
On the video I noticed a bit of chirping from the belt on the sprocket. I'd want to ease up on the tension of the belt. Morgan states that you should only be able to twist the belt 45 degrees but 90 will do. As long as it doesn't ratchet (skip a tooth) then it's tight enough.
What's your mileage? Who cares. Is it practical? See #1. What happens when it rains? You get wet.
My first sprocket was changed at the first service, I was told there was a fault with it but no more detail. The sprocket in the video has done about 14000 miles and does show wear but not excessively so. The tension is set to a bit more than 45 degrees of twist on the top run and doesn't jump teeth. I would say that the belt noise is a bit exaggerated as I just used the built in microphone which of course was located in the same aluminium box as the belt and sprocket! I'm with you on the lack of need to have two flanges on both sprockets and have seen the amount that the belt can move when aligned badly. By rights I really should repeat the video with the spindle deliberately misaligned to the left and to the right to demonstrate the way the belt can walk side to side. With the alignment between the front and rear sprockets on the early cars (when they are actually aligned "correctly") I would expect a second flange on the rear sprocket would force the belt to bend between the sprockets which doesn't seem like a good arrangement.
