Smaller rear sprocket = new chain?


New Member
Hi there,
This could well be a stupid question, but I bought the ooracing 303 kit with the smaller 34 tooth sprocket. Do a need a new chain, or perhaps I take a couple of links out of the existing, or perhaps just adjust the wheel further to the rear (does look like it on the limit of adjustment mind you)? The existing chain has about 500 miles on it.
Oh . . . didn't realise this was my first post (been lurking for a while). Perhaps I should introduce myself and the bike. I'm Phil and have been riding for years (hence somewhat embarrassed to ask the question above). My regular bike is a Kawasaki Z1000SX but I'm also lucky enough to have a Ducati classic sport (mainly to look at).

The Ace 125 was a present to my wife last year - her first bike and something cool to learn on.

We both love the styling of the Ace and it fits her perfectly. I've ridden it a few times, but it's way too small for me (being a fat boy).
I'm not familiar with the swap on the ace, but generally you want to change chains and sprockets at the same time to get even wear.

That being said if there's not a lot of miles on it I'd personally just knock some links out of the chain if necessary and call it a day. You'll need a chain breaker tool if you don't already have one.
If only going down a couple of teeth you should be able to adjust the rear wheel to take up the slack.

As others have said, generally you should replace both sprockets and chain at the same time but if they’re not worn just go for it. Sometimes too much thinking is just too much thinking.

A wealth of knowledge and data here.

Have a look at the database as it has a section for sprockets.

Having said that, the important field is blank, even though nine bikes are running this ratio.

Given your machine has so few Ks on it, I suggest that all is ok not to change. Tim is correct.

Let us know the outcome and please update the spreadsheet.

Also remember to load your bike and details in the spreadsheet and through a post on the Ace Locator thread
I took a link out, and it now fits perfect.

Also rejetted the carb and finally it no longer struggles to start and runs much little. Thankfully found the thread about the replacement pilot jet being a single piece (unlike the three pieces it replaces) . . . . had me head scratching until I found it ( ). Also cut the catalytic converter out of the standard pipe (and re-welded together).
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