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miner

Chain Tension & Wheel Alignment

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Another thread on top of the ones I’ve been googling.... bike is back together and as clean as it’ll never be again.... finding the setting of the chain adjusters a bit confusing, not used to snail cams yet and a little unsure about the tension/alignment on the GG. Is it normal / expected to end up 4 notches out?

Some points to consider:

  • Chain tension is coming what looks to be ok at 10 from the end (pointy end - thumb’s worth of gap and some slack in the arm).
  • Setting other cam to 10 then turning the tyre is completely dragging on the new chain guard (top of swingarm on - more on this below).
  • Playing around with spinning the wheel to get it to align itself sets it at 6 notches from the end (some fouling but only at a 30deg window)
  • The Pirelli MT43 I ended up with (long story on another post) is catching the new chain guard, wasn’t an issue before as the MT43 had worn down the two bosses where the screws go through to hold the top section on.  Option to dress it with a file.
  • Rear rim was replaced in a reputable bike shop.... new rim, spokes, same hub. Assumed ok.
  • Tension arm - was messing about with the tension when I stripped the swingarm... slackened it back off a bit to what feels right and aligns correctly. 

Queries:

  • Snail cam marks - not absolute but should align or be within X-notches?
  • Tyre catching - partly the shape/size of the tyre - some excentricity possible due to manufacture?
  • Rear rim - if laced up correctly should be pretty square? 

Thoughts and advice welcome.... used to screwed adjusters and still getting to grips with snail cams and the tensioner arm on these bikes. :(

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Aside from throwing away the MT43, you're worrying way to much about this. Set the cams the same. The chain guard always rubs, ignore it. Check your rear spokes if it's really bad, you can pull the rim back the other way a little. 

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Ha ha! Was asking myself the same questions.... took some advice from a trusted source (father in law’s an ex-mechanic and club racer) and set the cams even as that’s where I’d set before. Deffo more the shape of that MT43, will take it a spin tomorrow to check it out. Cheers. 

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Some pics of the old guard for info....  

GG Chain Guard

Used to KTMs and Honda machinery... this GG has been an eye opener for sure!

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11 hours ago, miner said:

Some pics of the old guard for info....  

GG Chain Guard

Used to KTMs and Honda machinery... this GG has been an eye opener for sure!

Hello Miner, from those pics you posted I can see that your chain is a little tight and the chain tensioner block is up-side down.

One thing I've done in the past when I've had the linkages disconnected for greasing is take the swingarm through its full arc and you can easily determine the correct chain tension, obviously you want the chain to have the slightest bit of slack when front sprocket, swing arm pivot and rear axle are all in a straight line, then with the bike fully reassembled and sitting up on a stand with rear wheel off the ground make up a spacer block that squeezes in tightly between chain and underside of swingarm at a pre-determined point. Now put that spacer in your tool box to be used whenever you need it, make it out of hardwood timber or a short piece of pipe or electrical conduit or whatever you can lay your hands on.

That's what I do any how, makes setting correct tension easy.  

Edited by fourex
My spacer block idea.
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8 hours ago, fourex said:

Hello Miner, from those pics you posted I can see that your chain is a little tight and the chain tensioner block is up-side down.

Thanks for that... I’ll try that methodology for tensioning.  Had me panicking there.... just been to check.... its the tensioner arm itself, I hadn’t backed it off enough after I’d minstankely tightened it up (never drink and spanner :)), just backed it off a bit more and its siting back better now.  Good spot.  The guide block is a different block, looks like a newer part... it’s not the same as the one that came off the old one with the plate. Keen eye though, cheers. :)

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With the bike on a box type stand and the swingarm at its lowest. Adjust the snails till the chain has minimum tension ie the tensioner just in contact with the swingarm. This way the chain will always be tensioned but will never be too tight and the tensioner block will last longer.

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Just seen your photo and the tensioner block is upside down!! Swap it round immediately!! Having it that way the chain  has no tension and actually not enough slack. As it is the chain is more likely to snap.

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You could try measuring the distance from the swingarm pivot centre to the rear axle centre, should be the same both sides.  That will tell you if your cams are correct.

Maybes your wheel has been rebuilt with a different offset to the original, I'm sure someone on here could give you an offset reading from an unmolested wheel as a check.

Edited by craig10

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Just checked again now I’m not in a hurry to get back in to watch the Moto GP.... it is upside down.... Bollocks!? Was looking at it thinking something wasn’t right but the penny hadn’t dropped. Will swap it tomorrow.... thanks for that. ??‍♂️

Wheel is dragging hard on the chain guard.... anyone had any issues relating to tyre selection? Or nobody else is running the tyres from an old Bultaco twinshock on a modern GG?

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I've always had good success with this tool from Motion Pro; clamp it to your rear sprocket and then sight down the rod to the front sprocket. This process guarantees alignment.

https://www.motionpro.com/product/08-0048

Clearly this tool requires that the wheel is properly spaced from the swing arm as intended by the manufacturer.

Dale

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Well from new it's not supposed to rub on the chainguard, so it needs adjusting to miss.  

If you can't do that by adjusting the wheel spindle cams (and keeping the wheel almost in line.)  Then you will need to offset the rim by a few mm.   This is done by loosening the chain side spoke nipples by half a turn, and tightening the other side nipples by the same half turn.    If the rim has any wobble in it, then that requires a lot more spoke tweaking.

I would think that an old bike is always going to be a bit out of alignment, things wear and frames bend over time.   The worst I ever had was a BSA C15, where the wheels were not vertically aligned,  and a Bultaco 350 that used to leave two separate tyre tracks.

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Got it on and chain set, snails set even.... I’ve chalked the rim where it’s fouling and it’s about 120 degree segment. Would that be alignment of the wheel? Or straightness / trueness of the hub from re-lacing?

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Having the wheels completely true on a trials bike is completely unnecessary. Use the chain guide as a marker to find the places where it's really out, adjust the spokes, and call it good. 

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It’s definitely out of true, been out and checked and checked.... took some advice, a couple of other checks. Definiately not right. For all it’s dragging a bit across 120deg I’ve have it outside running on the paddock stand, it’s definitely not square you can feel/see it.

Could explain why it wouldn’t hold pressure... another trip to the shop?! Or adjust at home and have to re-seal?

My mate has a tyre changing machine, need to square him up for the S3 head for the 300EXC... maybe two birds one stone. Or take the bikes out Saturday and drop this wonky wheel back in the shop. 

Checked all the other bits I did half cut... all ok apart from the rim and trying to bleed the rear brake... might try the calliper held high again. ?

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