This is rapidly becoming the longest belt change in history. Has the potential to outrun @West Cork Paul sprocketgate thread (but I doubt it).
Hi Ricky, I've just changed my belts on my 999 last week, closely checked because of this thread. My belts were on more than 5 years with decent mileage in that time, but I had zero fibre or dust in the belt area...so I wouldn't put it down to "normal wear".
Thanks for that. As said earlier, I have done belts on this bike before and have never seen anything like this, which is my concern.
Ive not seen markings like those on the smooth side of a used belt. There’s a distinct difference between the teeth and valleys. I’m no materials expert but I’d not be surprised to be told those belts have both got very very hot. Mind you, if it’s a track bike, despite its low mileage the engine is running at significantly higher revs for most of its running time compared to a road bike so perhaps it’s just normal wear and tear under the circumstances. Have you shared photos with Stuart (ExactFit) for his input?
Update…. Measured old belt tension today...both H and V were pretty loose, around 55 to 57 Hz. This seems to indicate that the issue may not have been that they were too tight after all, in fact, rather the opposite! New Fuji nuts and wave washers used when they were last installed so tensioner nuts not loose - I think I torqued them to around 24Nm. Checked tensioner and idler bearings - idlers span fine, no play at all. Tensioners span fine but slight axial play. No evidence of anything caught in the belt runs etc. If anything, the vertical belt might have evidence of a very slight chamfer/wear along outer edge of the smooth face. If one runs one’s finger along that edge it feels slightly wavy coincident with the teeth. All rather strange.
Today I pulled the tensioners off and checked the bearings - perfect, no play, ran smooth. Likewise idlers. Brushed out all the debris from all the nooks and crannies- no evidence of anything but the fibrous dust. The only thing I can put this all down to is the vertical belt somehow rubbing on the inside of the belt cover, even though I measured before and there seems to be good clearance. I have removed all the mesh that I can and will leave it off. Looking at the mesh and NACA port, it appears that something has been abrading the edge of the duct and the mesh. One can see the sanded area of the carbon and the remaining bits of mesh wire are shiny. Perhaps my belts were too loose and that allowed them to flail around and contact the inside of the cover? Weird.
It’s annoying when you can’t find anything 100% positive. I do think the marks on the BACK of the belts did not particularly indicate them to be slack. You’ve done all you can. Inspect carefully after the next good thrashing and go from there!
P.S. The areas marked in red have been abraded with a cutting disc or similar, probably when ‘finishing’ in production. If the belts had done that I would have expected more of a smooth polished edge?
