Just had my bike in for a new sprocket and chain set, and now i'm red lining in 4th (top gear) at 60mph, when before I could get to 75mph.

Would it make sense that they've installed the set for the 5 gear model? (I've no idea if that's the case or not).

I'm goina nag at them to get a smaller back one, really don't like being constantly in the red.

- Anthony

That is a considerable reduction, 20%, Sounds like completely the wrong sprocket set, take it back to where you got it done and demand that they replace both sprockets with the correct ones, unless of course the sprockets you had on your bike weren't the standard ones. I would suspect that the final drive ratio's of both bike would be about the same, unless the 5 speed has in excess of 20% more power which I very much doubt.

I thought boggo standard CG125's where rated at about 60-65 top end anyway...
Does deffinately sound like sprockets though. but if they have fitted the wrong ones or not ????

Hope you get it sorted

get a new front sprocket with 1 less tooth at the front that should sort it. maybe the one you had previously wasn't the standard one?

To compensate for 20% it will have to be considerably more than 1 tooth less, more like 2 teeth more and a 2 tooth smaller rear sprocket as well.

The mechanic wants to replace only the back one, wouldn't that need like 6 teeth off?

It's a pain cos the mech is off till thurs and got the bits in, and his apprentice so to speak is fitting it.

I'll do some dodgy maths when i know the size of the sproket to see if it's going to put it right, I've no idea how many teeth are on either at the min.

- Anthony

Do the maths yourself, if you've lost 20% of your top speed then you need to remove 20% of the teeth on the rear sprocket ie one tooth for every 6 so a 60 tooth sprocket will need to be replaced by a 50 tooth one thay's a lot of teeth off better to go up a couple on the front sprocket first and then re evaluate, iether that or get them to replace with sprockets the same size as your old ones.

ask for your old sprockets back so you can check them against the current ones, dunno why but a habit my girlfriends grandad bestowed on me is always get the parts back the mechanics say they have changed, i did this once with the rear brake shoe on her car and the mechanic went all sheepish when he showed me the shoe, it was only half worn, cheeky get.

needless to say i didndt pay for that job

The first set they put in was 14-41, they've changed it (apparently, I'll check on saturday) to 14-38, but I can't really notice the difference, I'll try and push the top end on the way home if the weather doesn't cause slow moving traffic again....

- Anthony

I don't think less than 10% decrease is going to do it, you may see 5 m.p.h extra but no more try a 15 - 35 and that will be noticable, as a point of interest you need an odd number of teeth sprockets. Sprocket and chain wear will be nearly halved if you have this mix.

Could it be that your bike is an import, not a UK model? That could account for the error.

I have mentioned your bike to you before (don't know if you read the reply to the thread, didn't notice how old it was when I replied) but judging by your 'must be old stock' statement I suspect that you have brought a japanese CG125 'E' import. If so then with standard sprockets 60 (ish) is what you can expect. I have a picture of my wifes 'E' in my profile, let me know if yours looks similar

Yup, that's my bike. I can now get 70 by taking it beyond 10k revs (on 14-38)
one more on the front sprocket = 4 and a bit mph more, would be about right I think... probably.

I'm discussing "payment" for the second set this saturday, which i'll be avoiding if at all possible, as he should have asked before installing the first set if they were different to the ones that were installed.

So they installed the wrong sprockets? Or your bike had non-standard sprockets on?

Apparently non-standard sprokets, not that I knew, all i knew was i wanted the same as i had, i even asked him before he installed the first set, but he said he hadn't checked if they were the same yet.

IF you asked him to install the same sprokets then he diddnt that is his own damn fault! I would whinge until i got the same sprokets, and would only pay for the original work.

Ditto what Cheddies said - if you instructed him that you wanted the same sprockets as were on there, then thats what you should get, his fault if he failed to check - specially as you asked him.

Don't pay any more!