Chain tensioning

[MetalHurlant]

G'day everyone,
Is chain tensioning difficult? Are there any special tools required? And how do you keep the wheel alignment straight?

All I have is the distance the correct amount of play should be, and it is [/u]very slack at the moment.

Ian

[Skins]

It's not hard. Basically you have to loosen the two caps on the ends of the swingarm, by loosening the two scews on each cap, then turn the eccentrics that carry the axle. The eccentrics will move together, keeping the wheel alignment correct, and turning them one way will tighten the chain, and the other way will loosen the chain. Only a very small movement of the eccentrics is required. A loose chain is safer than a tight chain. (A tight chain is bad for the gearbox). You may have to loosen the axle nuts also, to turn the eccentrics.

[MetalHurlant]

Thanks Skins, you were spot on. It's all good, now - back to the road.......

Ian

[PascoPaso]

My Paso has the same problem of too much slack. After loosening the 2 (x2) end caps, I cannot get the eccentric adjusting "flange??" to rotate. It is a 17mm hex on the axle nut, right? Before I break something, I was wondering if you could offer some advice as how to get it loose? Thanks, Mark

[Skins]

If you tighten one of the end caps up again, you should be able to loosen the opposite 17mm hex nut, I think. It's a while since I've done it. However, I think one of the 17mm hex nuts is solid, being the end of the axle, if I remember correctly, and this may influence the matter.

[PascoPaso]

Thank you for the info. It sent me in the right direction. Keep the chain-sprocket side tight, loosen the right side or non-driven end. It is the same as my Goldwing. Locating a 17mm hex wrench was the hard part. Cheers.

[rocket_man]

Last Sunday, I took some of the slack out of my '87 750cc Paso's (?) old chain (by the way, I am inexperience with this). I measured a deflection of 0.8'', without anyone on the bike...maybe I should have had someone on the bike. The chain popped after 15 miles; along with the drive sprocket shearing off of the drive pinion!!

Luckily, it was low speed and there was minor damage (chipped the bottom corner of cranckcase cover, and put sprocket tooth marks in the swing arm) - I know it could have been a lot worse!!

So, I've got a new D.I.D. chain on it (riveted), replaced the sprocket retaining ring, and got a new bottom slider. With someone on the bike I measured 1'' deflection, and without 1.2''. Is there anything that I need be concerned about? I am very worried that the chain may break again, due to my cluelessness...

I would really appreciate it if you could please let me know if I should tweak something before I ride it tomorrow!!!!

Thanks,

Michael

[Laddie907]

Last Sunday, I took some of the slack out of my '87 750cc Paso's (?) old chain (by the way, I am inexperience with this). I measured a deflection of 0.8'', without anyone on the bike...maybe I should have had someone on the bike. The chain popped after 15 miles; along with the drive sprocket shearing off of the drive pinion!!

Luckily, it was low speed and there was minor damage (chipped the bottom corner of cranckcase cover, and put sprocket tooth marks in the swing arm) - I know it could have been a lot worse!!

So, I've got a new D.I.D. chain on it (riveted), replaced the sprocket retaining ring, and got a new bottom slider. With someone on the bike I measured 1'' deflection, and without 1.2''. Is there anything that I need be concerned about? I am very worried that the chain may break again, due to my cluelessness...

I would really appreciate it if you could please let me know if I should tweak something before I ride it tomorrow!!!!

Thanks,

Michael

della manuel spaghetti recommends 15 - 20mm freeplay with one person sitting on the BACK of the saddle [ not the rider position ] or the swingarm mid travel.

generally chains will only snap under extreme conditions: over-tightened AND hitting a decent bump with a heavy load.
it also depends on sprocket and chain condition and quality...if the chain rides up on a worn countershaft (drive) sprocket the free-play is reduced, similarly if the teeth are hooked from wear the chain will snub the sprocket - wrapping around more and reducing free play.


"stretched chain" [worn bushes] will also behave erratically when travelling; get a mate to ride along side and watch the chain travel - if it's whipping around or vibrating at cruise chances are the chain is stretched.

it's always hard to diagnose these things over the internet.
if you now have a new chain and sprocket(s) you should be OK; my advice is lash out and put a new rear sprocket on too unless you know it's in good condition. Worn sprockets wear out chains very quickly.

something I would check is that the countershaft [and sprocket axis] is not bent after the recent damage. You should have done that before the new sprocket and chain went on...
if the sprocket runs eccentric it will damage the chain.

you say the drive sprocket sheared at the retaining ring? Were the screws or parts of them still in the threads?
It may be possible (or likely) that the drive sprocket came off and THEN got caught up in the swingarm; THEN broke the chain...it depends on how loaded the bike was...

[rocket_man]

Laddie907

I do believe the chain probably just about had it and may have been stretched, as there was a large amount of slack prior to tightening the chain.

Also, I think you are right about the sprocket failure initiating the chain failure...although I am having a hard time figuring out how my adjusting the rear wheel, by tensioning the chain, could have caused this. The sprocket was still screwed together when I found it, just the retaining ring had been sheared.

Afterwards, I checked the countershaft axis with the engine running at idle. They was no apparent wobble or eccentricity to it, so I think it is okay. Also, the sprockets appeared to be in decent condition - I had not replaced them....maybe I should.

Some final odd observations was that all of the screws on my rear sprocket had become loose by about ~ 2 turns, after chain failure (possibly due to the shock). Also, with the drive sprocket reinstalled it appears have some slop in the pinion groove, from front to back (~2mm), but that may be normal?

Thanks for the feedback!!

Michael

[Tamburinifan]

it appears have some slop in the pinion groove, from front to back (~2mm), but that may be normal?

Normal freeplay.

[rocket_man]

Gert

Good to know. I took the bike out for a spin (10 mi). So far so good!

Michael

[Laddie907]

the rear sprocket nuts are nylocs - it's almost impossible for them to come loose.
if they were loose i'd be worried ...

check they have not chewed out the swing arm [there is very little clearance there]
the swing arm is very soft alloy and very easily damaged.

why I'd be worried is that if the last mechanic left them loose 2 turns (because that would be the problem) what else have they screwed up? The rear sprocket MUST sit on the rear wheel boss - it should be a TIGHT fit - I am hoping that they haven't tried to fit the wrong size sprocket.

this is all a bit too hard to diagnose.
make sure the sprockets align in-line - if they are offset the chain will be damaged.
if there is misalignment it is possible the chain will de-rail; maybe this is what happened before???

[rocket_man]

yeah, this is a bit tricky!

As for the rear sprocket bolts, I had been the last one to tighten them, being that we were working themselves loose. They don't appear to be nylon allens, but I did use lok tite. Last I checked they were snug, until the chain failure....I will definitely be keeping an eye on them now.

I will also double check the alignment, as best able. Thanks! If I still have a bike in 2 mo., then we will know it worked out!!

Michael

[dave906]

The lock nuts on the sprocket carrier bolts have a spring steel lock arrangement as part of the nut instead of the internal nylon bush that makes an interference fit with the bolt thread in a 'nylock'. Same concept though.
I have also had mine work loose over time after having tightened them down well.

Discovered on routine check before anything bad happened. Now I add Loctite to them as well, but you have to take the wheel off to get at the nuts to clean off any grease or chain lube contamination before reinstalling with Loctite.