I apologise for dredging up stuff which I am pretty sure has been covered in old threads, but I can't seem to find the information in the forum.

I replaced the chain plus front and rear sprockets on my '89 1kF recently. The problem is, I wanted longer gearing for touring, so I went down from a 43 tooth rear sprocket to 42 and wanted to go up from 17 to 18 tooth on the front. Sadly - and I am pretty sure I saw this in a thread some time back - the 18 tooth doesn't fit in the space avalable for the front sprocket, so I had to go back to 17 tooth.



So, three questions for the gurus:

1. What are the factory sprocket settings (front/rear): 17/43?
2. Is there a non-destructive (smile) way of fitting the 18 tooth on the front?
3. Is there a recommendation for front/rear ratios for touring?

Thanks guys.

 

17 front
42 rear
Since my CBR turns right at 4000 at 65 mph I can't see any reason to change the gearing myself.

 

Thanks ranchome: that means I am now back to stock.

 

The Gearing Commander website will show you the stock sizes in the drop-down menu. Also, you can tinker with various gear combinations and it'll show you how different combinations affect rpm at a given speed, etc.

 

1) 89 -> is 17 / 42 (87 88 , 17 / 43)

2) for an 18 only a small amount of grinding on that chain divider tab to the rear of the
sprocket is required , maybe 2 mm if that ! Takes 2 mins with the sprocket off - very easy
won't hurt a thing...... just mask off before doing it so filings fall to the floor and do not
get sprayed and stuck to the counter shaft area - ask me how I know this

3) 18 42 or 18 41 & you'll find it runs super smooth when touring, only drawback being
laziness to accelerate off the mark - but between 85 and 135 big 's as things get a little
more interesting in a very good kind of way imo.

 

A simple calculation
3 teeth down on the rear sprocket, ie down from 42 to 39 will be the same as 1 tooth up on the front sprocket, ie up to 18.
I'd leave the front alone and drop the rear down to 39. This will give you lower revs for the same original speed (around 7-8%) and a slight improvement in MPG.
First reason is as Sprock explained - all that grinding becomes unnecessary
Second is chain length it's a lot easier to move the rear wheel back to accommodate the extra chain you'll have due to the rear sprocket being down by 3 teeth, ie 14% than possibly having to fit a new chain.............

Just my 2c worth.

 

Well here's the thread where I added the big front cog way back and I still have it on
the 1990

https://cbrforum.com/forum/cbr-1000f...p-front-96094/

 

Thanks for the replies, guys; really appreciated.

RoadiJeff: Thanks for the link to the Gearing Commander website - very useful resource.

Shadow and Sprock: Thanks for the advice and also the link to the 18 tooth post: thought I'd seen it before.

The thing about going up on the front or down on the back is that I have the 18 tooth front now, brand new, so I think that's the way I'll go. I am just a teeny, weeny bit worried about damaging something with the grinder is all...

 

A man, a beer, and a high speed grinder.

What could possibly go wrong?

 

"I am just a teeny, weeny bit worried about damaging something with the grinder is all... "


Well use a high speed dremel type tool with a cylindrical grinding stone (chain saw sharpening type)- that way you'll have better
control of your tool !