Drive Chain Tension Issue: Big Differences Between The Tightest Point And Slackest Points

Hi
Iv got an issue with the chain tension on my st triple R. First of all iv not had the bike long, & when i got it, although it had a DID X ring VX3 chain on it & an unknown make of steel front sprocket & a supersprox rear sprocket, They didnt look like they had ever had any maintenance performed on them at all, & the front sprocket, Although not the worst id ever seen, wasn't in great shape but wasn't totally chewed up yet either. The chain was totally shagged tho however, & although the rear sprocket was in pretty good shape, i don't like changing the chain & sprockets individually, (apart from maybe the front when there's still a lot of life left in the chain and rear).

So yeah anyway i changed all 3 drive chain components, and just thought id keep the rear as a spare. One of the main motivating issues for me doing the change in the first place was, aside from the chain being quite stretched & in a horrifying condition, & i have OCD & clean & lube my chains quite excessively (i literally have OCD as a symptom of complex PTSD, not the pop psychology version anally retentive people say they have), & iv had a 1st hand experience with what happens when a chain snaps on a bad day & instead of spitting out the back, it punches a hole through your crank case, but yeah aside from that the other motive was because i had an issue with there being massive differences between the tightest points of the chain & the slackest, & i know you get tight spots on chains, from things like rear sprockets not being quite concentric, ect. ect. but not the difference i was seeing, im talking like atleast 3 times the slack on the slackest points with the tightest point set to the correct slack. So as i wanted to change the chain and sprockets anyway i did so. And i hoped, although i feared it wouldn't, sort the slack issue out at the same time.
When i pulled the front sprocket guard off to do the front one thing i feared was that the output shaft bearing would be knackered, however i couldn't feel any play in it. I did however find the front sprocket nut was so loose it was rattling and the only thing holding it on was the tab washer bent over it. I switched the sprockets over, the splines on the output shaft seemed fine and the threads on the end of the shaft were ok too, (although i do want a new nut as the threads weren't in great shape on the nut but were functional).
Anyway i got the new chain and both sprockets on, and tensioned it and torqued up the wheel nut, only to find that the same issue with the variations in tension from tightest to slackest points, still existed, although not quite as big as what they were with the old chain, the one thing i noticed though was that when you rotated the wheel to find the tightest point, there was 2 points where the chain was at its tightest both were equal & it was at one of these points i set the tension, which i set to about 20mm, & when i rotated it till one of the 2 tightest points was at the halfway point between the sprockets, the chain link that i marked as the other tight point was directly opposite on the top side at halfway point. Im sorry for the huge epic tale, but has anyone got any suggestions on what the cause of this could be? As i cant really see what the issue is and i dont know if im missing something blindingly obvious or what, but iv got too many knackered arthritic joints (at37) and back problems (like it and my neck being broke in about 26 places) and a knackered hip, to be scrating around on the floor messing on with this bike. (all injuries and many others caused by an A hole in a 4x4 destroying my z900 and throwing me into a stone wall at high speed), but yeah any worthwhile suggestions with this issue (the bike not the ignorant farmers in 4x4's that im surrounded by) would be apreciated. Cheers. Phil

 

Thanks for the responses, lv not had a chance to go & do anything with it since original post, i have a lot of hospital appointments to attend & its about an hour drive each way so they take most of the day & sometimes a few times a week, & i got some really bad news about the prognosis of my crippled smashed up shoulder & broken hip (after my leg was forced through my pelvis) on the same fairly bad day, but yeah sorry back to the bike anyway..with it being a new chain & sprocket even though its a good quality chain and the sprockets are a JT on the back & a steel renthal on the front, i expected there to be a negligible difference between the slackest & tightest points when tensioned correctly at the tightest point & although the previous chain was far worse. When i fitted it all it was cold & dark by the time i put it back together (& i dont have a garage with doors just an open sandstone arch with a shit light) & i was in incredible pain, the batteries on my work lights were dying, so there came a point where I had to call it a day & get back in the house and take enough pain killers to kill a horse, but anyway how i left it, it was all back together with the tightest bit of the chain at about 18/20mm of slack, then after lubricating it i took it for a quick blast up the road and back just so it kind of run everything in a little bit, it probably wouldn’t have got much heat in it like, but yeah then i measured everything again & not a lot had changed it was just more consistent,& not as big a differences, the slackest points are about 34/36mm and the tightest points are about 18/20mm,which doesn’t sound like a big difference now, but you can feel and hear it when riding. With regards to the bushes in the cush drive, that was one of the first things i checked, when inspecting the wheel before i took old sprocket off & although they needed a good clean they were in fairly good shape still so i jus cleaned them & lightly greased them to aid the re-assembly but they seemed fine & there was no excessive play in the cush, and the same goes for the rear wheel bearings. One of the things i did while the chain was off & id torqued the wheel nut up, was to give the wheel a good spin and just eyed up the rear sprocket, and it seemed to be spining straight. Obviously thats not an accurate test but i didnt really have anything to measure it with to hand, i have got a laser somewhere, that i used to use to check chain & sprocket alignment, but i cant find it. Anyway like i said i haven’t been at it since writing the first post, but felt i needed to clarify some of the things id ruled out already, also there was no play in output shaft bearing either & although all the things iv checked may behave differently under load, i dont think thats much of a consideration as the bike’s been up on a paddock stand when iv been measuring and checking stuff & thats where the slack differences have been observed. When i do go back out to it, one thing i was going to try was putting it on the paddock stand with sprocket cover and chain guard off, idling in first gear so i can watch it rotating, & if i can find my laser i could maybe use it to watch for any deviations. But as you should be able to see its a bit puzzling. So im not really sure where to go with it, & dont have particularly advanced measuring equipment at my disposal so itl probably be make shift stuff il use. If youve kept reading sorry for the long write up, but i must have not been very clear on some of the stuff id done and how i measured things in first message. Cheers phil

 

Hi cheers for the suggestions, i was going to try setting up a pointer like you say, it was just too cold and dark and my back and arthritic knackered joints were getting to me too much the first time i was working on it, but thats definitely one of the tests i was planning on doing, looking at it in a logical way though, with both the old sprockets & chain & new doing the same thing, & the only difference being that the new chain has a bit less of a difference between tightest & slackest points, it seems like the most likely thing to be at fault would be what the rear sprocket is mounted to as opposed to the sprocket its self i guess & the previous rear sprocket was a very good quality sprocket, & the new one is a JT sprocket, who iv had little experience with, but although theyre quite cheap, they seem well machined & appear suprisingly good quality for the price, but yeah thanks for the suggestions. Phil

 

Hi cheers for the suggestion, iv had something very similar myself happen, on my z900 which was only a couple of months old at the time but in my case it was caused by a shit quality chain (that was probably put on by the c**ts at the dealership, cos i doubt Kawasaki would have done that) but yeah thanks to the 12 inches of grit salt they put on the roads round here every winter to deal with the 6 inches of snow the chain had siezed up on a couple of links, that compounded with a shite lube i was using briefly & and short breakdown in my obsessive chain cleaning and lubing schedule, but yeah i know exactly what you mean but no i did check all the links and its a brand new DID vx3 chain, i even fitted the master link very accurately using my vernier calipers to ensure the plates were precisely the same width on each pin and exactly the same width as the other links. But yeah cheers for the suggestion tho m8. Phil

 

Cheers for the response m8. I have been intending to do exactly that iv just not had the time, as its a bit of a pain getting the cover off cos the previous owner replaced two of the bolts with allan head bolts but then seems to have rounded them (he probably rounded the original bolts too) so i had to use a rounded bolt remover but i didn't have any replacement bolts so i just put them back in using a torx bit as a temporary measure, but i now cant find the remover bit i used to take them out last time, but yeah il get round to it when i get time. But yeah what i was going to do with the front sprocket was the same thing iv done to check the rear already, which was to set up a frame to hold my laser level with and project a laser cross on to it + so i had an accurate reference point and then rotate the wheel with it on the paddock stand, although this may seem unnecessary for the front sprocket, with it rotating more times per wheel revolution and all that but i might as well it dont take 5min to set up. I did this with the rear sprocket and just put it in 1st gear on the paddock stand and let it rotate just idling, with the + of the laser on the outer most rim of the rear sprocket just before the teeth, and it was perfect there was no visible deviation at all. But when i get round to it il perform the same test on the front sprocket. Iv just been using an old klr650 i had in the garage as a temporary mode of transport. But as much as i like the klr (iv always been a Kawasaki man at heart, but i should probably keep that to myself on a triumph forum) but yeah as much as i like the the klr, its just to gutless, iv gone from a brand new Kawasaki z900 with an upgraded full akrapovic system and a remap, down to a 675 street triple R down to a klr 650 inside of a few months, its gona be a c90 step through next at this rate.

 

Cheers for the response m8. I have been intending to do exactly that iv just not had the time, as its a bit of a pain getting the cover off cos the previous owner replaced two of the bolts with allan head bolts but then seems to have rounded them (he probably rounded the original bolts too) so i had to use a rounded bolt remover but i didn't have any replacement bolts so i just put them back in using a torx bit as a temporary measure, but i now cant find the remover bit i used to take them out last time, but yeah il get round to it when i get time. But yeah what i was going to do with the front sprocket was the same thing iv done to check the rear already, which was to set up a frame to hold my laser level with and project a laser cross on to it + so i had an accurate reference point and then rotate the wheel with it on the paddock stand, although this may seem unnecessary for the front sprocket, with it rotating more times per wheel revolution and all that but i might as well it dont take 5min to set up. I did this with the rear sprocket and just put it in 1st gear on the paddock stand and let it rotate just idling, with the + of the laser on the outer most rim of the rear sprocket just before the teeth, and it was perfect there was no visible deviation at all. But when i get round to it il perform the same test on the front sprocket. Iv just been using an old klr650 i had in the garage as a temporary mode of transport. But as much as i like the klr (iv always been a Kawasaki man at heart, but i should probably keep that to myself on a triumph forum) but yeah as much as i like the the klr, its just to gutless, iv gone from a brand new Kawasaki z900 with an upgraded full akrapovic system and a remap, down to a 675 street triple R down to a klr 650 inside of a few months, its gona be a c90 step through next at this rate.