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Chain adjustment protocol
Posted: Sun Jun 07, 2020 11:38 am
by macg4
Following a "slightly loose drive chain" advisory on the MOT return, my question is, chain adjustment on main stand with the suspension off load , or prop stand suspension on load ? I've always wondered ….
Re: Chain adjustment protocol
Posted: Sun Jun 07, 2020 12:00 pm
by Wheaters
I have noticed on my 350 there’s quite a big difference in chain tension between weight on and weight off the wheels; it’s all to due with the geometry between the centres of the swing arm and the gearbox sprocket. However, the chain doesn’t actually do anything when the bike is sitting on the centre stand and a chain and sprocket transmission really can’t tolerate being too tight; that will result in rapid wear and vibration. It will also put undue stress on the gearbox shaft.
So the answer has to be, it needs to be correctly tensioned In running condition, i.e. with the bike on its wheels and not tight with the weight of a rider sitting on it.
Re: Chain adjustment protocol
Posted: Sun Jun 07, 2020 12:19 pm
by Daiwiskers
As above weight on the bike to set tension
However once set with weight on the bike take a mental note how the slack is with no weight then use that for future adjustment
Hope this helps Dai
Re: Chain adjustment protocol
Posted: Sun Jun 07, 2020 12:36 pm
by stinkwheel
I generally find the tight spot then adjust it on the main stand so it seems perfect then put it a notch looser on each adjuster. Then check it under load.
Re: Chain adjustment protocol
Posted: Sun Jun 07, 2020 12:43 pm
by papasmurf
Always set the chain tension with someone sat on the bike. Very few bikes have the gearbox sprocket in line with the swinging arm pivots.
Also it is necessary to find the tightest spot in one rotation of the rear wheel. The may be a bike where the rear sprocket is concentric with the rear wheel centre line but I have never found one.
Re: Chain adjustment protocol
Posted: Sun Jun 07, 2020 12:49 pm
by macg4
Agreed, but then it begs the question,how are MOT testers trained to check tension? I presented the bike with the obligatory 25mm of mid slack relative to the swing arm.
Re: Chain adjustment protocol
Posted: Sun Jun 07, 2020 12:56 pm
by Daiwiskers
If the tension was right when the bike was tested don't worry about it you probably know more about your bike than the tester does
Edit I forgot to mention find the tight spot
Re: Chain adjustment protocol
Posted: Sun Jun 07, 2020 1:11 pm
by p
Here's what I did, only necessary once.
Bike on stand, plank of wood on seat, car jack on plank, strop/rope from either side of s/arm over jack, raise jack to compress suspension, jack until hub centre, s/arm pivot and gearbox sprocket in straight line with one another. Then adjust chain to no slack position. Release all the above jack etc.
Chain adjustment is now perfect; if you then measure free play on chain with bike just on stand then this is what you will always set it to in the future. Even if new chain etc fitted this measurement will still remain correct unless you change suspension ride height - write the measurement clearly on the garage wall. (I moved house,so must do it again!!)
Re: Chain adjustment protocol
Posted: Sun Jun 07, 2020 6:25 pm
by Dale
Slightly off topic. The much vilified Anstey link suspension on Ariels was designed to overcome this problem by allowing the axle to rise and fall in an arc. Too bad it wore out in about a thousand miles ! (Slight exaggeration)
Re: Chain adjustment protocol
Posted: Mon Jun 08, 2020 6:21 am
by PeteF
p wrote: ↑Sun Jun 07, 2020 1:11 pm
Here's what I did, only necessary once.
Bike on stand, plank of wood on seat, car jack on plank, strop/rope from either side of s/arm over jack, raise jack to compress suspension, jack until hub centre, s/arm pivot and gearbox sprocket in straight line with one another. Then adjust chain to no slack position. Release all the above jack etc.
Chain adjustment is now perfect; if you then measure free play on chain with bike just on stand then this is what you will always set it to in the future. Even if new chain etc fitted this measurement will still remain correct unless you change suspension ride height - write the measurement clearly on the garage wall. (I moved house,so must do it again!!)
Same thing can be achieved with stout ratchet straps.