chain slack advice for a newbie

[NotBenny]

hello, first time in these parts, recently joined the two wheeled world and after some practical advice.

My Yamaha MT-125 (I am a grown up, honest, I just decided I'd rather do a CBT and get some experience under my belt before going for a full licence) chain slack is out of tolerance, but the adjustment on the rear axle looks to be maxed out (on the limit of the position markings on both sides). Does this mean I need a new chain? and if so do I need to replace the driven/driver sprockets at the same time? Bike has done 18000 miles, is this reasonable?

[Freakuk]

Either the chain has stretched that much or there are too many links in the chain, either way it isn't correct from what you mention.

Are you sure the chain hasn't been replaced already but it has too many links? You could count the links and verify on-line how many it should have (assuming the sprockets are the same size also).

18,000 miles out of a chain is pretty good going, if it hasn't been swapped then I would and I'd replace the sprockets also, they should be cheap compared to the chain, you also have the opportunity to change the final drive ratio while you're at it and but some decent aftermarket items too (Renthal etc).

[trickywoo]

If you do replace sprockets go with OEM or a very good named manufacturer.

Its tempting to go cheap because 'its only a sprocket' but the front one in particular really needs to fit perfectly. If it doesn't you run the risk of the cumulative lash damaging your output shaft.

It does sound worn but without seeing it its hard to say.

I've never run out of adjustment but it could still be your problem - good advice in the first response.

[NotBenny]

Making progress: sprockets appear to be standard size (14/48) and chain has 132 links. Really struggling to find out what the correct number of links should be - any googling I do trying to find specification just returns adverts for replacements. The fact that all the replacements are supplied as 132 teeth means either the chain has been changed and left at 132 links (but should have been shortened) or that the chain should be 132 links and is utterly shagged. Have found a pdf copy of an owners manual but that doesn't state the number of teeth, only the chain slack measuring method. Will see if I can get it in at my local Yamaha dealership and just pay someone to sort it given my rather limited experience of motorbikes.

[CousinDupree]

Check to see if you can pull the chain off the rear sprocket at all. More than a couple of mm and the chain is shot.

Also look to see if the teeth on the sprocket are hooked. Put some pics up here if you want

Edited by CousinDupree on Thursday 30th May 12:26

[Biker 1]

CousinDupree said:

Check to see if you can pull the chain off the rear sprocket at all. More than a couple of mm and the chain is shot.

Also look to see if the teeth on the sprocket are hooked. Put some pics up here if you want

Edited by CousinDupree on Thursday 30th May 12:26

+1
Usually the sprocket teeth end up sharp & pointy when they're worn out.

If you decide to do any work yourself, including cleaning/lubing, be VERY careful:

https://www.youtube.com/watch?v=yk-PME37URI&ha...

[Pothole]

OP: pics will help as discussed, but where are you? I'm sure there's a PHBBer local who can come and cast an eye over the bike and give you some advice.