I have turned the inlet side only and there did not appear to have any tight spots. Will be giving this a go tonight and if I can't sort it out, I think it's time to take the bike to the experts.
So I have the cam cover off. The cams turn without any issues. The engine turns without issues. I connect cam belts and when the rear cyclinder comes up to tdc the exhaust stroke its as if the piston just touches the exhaust valve ever so slightly. The vavle is still closing when the piston is at almost at tdc. When I turn the engine backwards it perfect. No issues no tight spot. I actually beleive the tight spot is the piston just touching the exhaust valve. So possible verdic is the exhaust cam has slipped?? I definite don't have to experience and or tools to check all that.
Well well well. Big thanks to Nelly. Was thinking about what you were saying about the 4o clock and was taking pictures of all settings and comparing each time and I then realised that I wasn't setting closer to 4 but 5 o clock set to 4 and bingo she turns beautifully again. My next worry is that I have had the nuts that hold the tesnsioners on and off so many times I should put new ones on or not.
Can't believe it took me that long. The key was well obviously Nelly and that I took pictures to make reference between the different positions. Ok let book that next track day. Will order the nuts tonight, we'll send an email.
Looks like this was a really lucky escape I can't help thinking though that identifying what went wrong here is really important. There are a few things that could have caused this but without wishing to point any fingers, we have to recognise that the fact the belt shredded shortly after being replaced may or may not be a coincidence. Did one of the guide/tensioning pulleys fail and if so, which one? If the fixed pulley failed, why would it have failed shortly after the belts were replaced? Could it have been due to excess tension? If the tensioning pulley failed, did it slip because the Fuji nut wasn't replaced with a new one? Was the tensioning pulley properly seated and was this checked by placing a straight edge across both pulleys? Was the tensioning nut turned anti-clockwise, rather than clockwise to tension the belt? Was the tension set correctly and how was it set?? As Exige pointed out, it's very unlikely that the belt shredded on its own, something caused it to shred, so working out what that something will be really useful. Well done to the very experienced and knowledgeable Nelly for pinpointing the reason for the tightness when turning over the engine and well done to the op for taking pics to help identify the cause and for bringing this to everybody's attention. Looking at the pic of the shredded belt, the belt seems to have come off the inside of the fixed pulley, which is very odd, given that the pulleys have lips on them. The lip on that pulley does look as though it might be damaged though. Were both pulleys still intact?
Old Rider This has been running through my head non stop, I am very nervous putting it back together and not knowing exactly why. Personally I think the adjustable tensioner let go, why?? not sure, the nut was tight in the aftermath, perhaps the belts were incorrectly tensioned???, I am confident that I did tension clockwise as I am very careful with delicate things like that. Was the pulley seated correctly, never checked the alignment with a steel rule or similar, visually looked fine. The tensioner actually came away from the bearing it spins on. Really don't know. However I have now fitted all new adjustable & static tensioners, new Fuji nuts, new belts. Will tension correctly and check and double check them and make double sure it's tensions clockwise. Apart form that don't really know what else to do. And your right what a lucky escape
Hope it's a typo on your part but on my bike at least, a 999, the tension should be applied anti-clockwise, not clockwise as you've said you did. Also, iirc, the pulley sits on a top hat spacer and if it's not seated properly will be out of alignment. The cam pulleys have no lip, so if the tensioning pulley, which does have a lip, is out of alignment, that will give you a big problem. So, do put a straight edge across both pulleys to be sure.
sorry yes typo, anti-clockwise to tighten, at work and doing many things at once, and now my son has been sent home from school and not well.
I use the old fashion manual way, with Allen Key and the 10mm spanner alone with experience and feel. However this time I also downloaded an app in my phone and use the frequency tuner. On my 749s I did one belt replacement by feel alone and was fine?? or was it luck?
Didn't know you could use the Allen key method on a 4 valve motor... ExactFit have reduced their frequency recommenration to 99hz now. I've an idea Gates has done the same but that may be the Alzheimers creeping in. Gates don't recommend retensioning an in-service belt unless it is well below this figure, so there is a fair bit of leeway it seems.
@Startline Al - didn't you have one like this in recently with a badly fitted/aligned tensioner that was the culprit?
Today I was at Silverstone and apart from missing on rainy session in the morning did the remaining sessions and bike ran sweet.
Never done 4V belts, but countless 2V, and after fitting I'd turn the engine over by hand (plugs out, bike in gear, rotate rear wheel) to check nothing was doing anything it shouldn't in the engine. Just gave me the confidence it was all ok before hitting the starter button.