Building a 40 tooth for the 1290

[abc]

One of the other things I am noticing is that the chain noise has reduced by about 30%. I dont know if this is because of the new sprocket offset or because the chain is seeing a different angular contact with the chain giudes and sliders but it is heaps quieter compared to the stock sprocket and I like it.

[robban75]

Is the cc measurement 155, 154 or 156 mm?
I have been looking at a duc 1098 streetfighter sprocket as a base and those are 154mm cc and a similar design to begin with.

[abc]

I am not sure what cc means but if you actually mean PCD (pitch circle diameter) of the mounting holes then it measures 155.2mm
Keep in mind that the inner diameter has to be correct for the sprocket to mount up properly on the cush drive as well. Is the duke one 525 pitch as well?
Good luck and lets hope the duke one can be easily modified to fit the 1290 as that will save a lot of work.
Hope this helps you.

[MaximusVR46]

looking good nice bit of work.

Have you measured how far out your speedo / milage is now?

[ktmguy]

looking good nice bit of work.

Have you measured how far out your speedo / milage is now?

I'm always open to help people so I can just delete your question or you can cop the piss take. what you prefer?

Let just start of by stating that speedos are frowned up on in Australia!

[DMacL]

looking good nice bit of work.

Have you measured how far out your speedo / milage is now?

You can always spot someone who hasn't wheelied a 1290 enough...

[robban75]

looking good nice bit of work.

Have you measured how far out your speedo / milage is now?

Don't know if it's me or abc you're referring to but if it's me the answer is no, waiting for better weather.
But I'm 95% sure the speedo will be almost correct.

Abc> I have found this sprocket, it will take wery little effort to mount up, just a bit expensive considering that you have to modify it first.
http://alienmoto.se/contents/sv/d736.html
154mm cc (Centre to Centre between the mounting holes) 154mm inner diameter.

[MaximusVR46]

looking good nice bit of work.

Have you measured how far out your speedo / milage is now?

Don't know if it's me or abc you're referring to but if it's me the answer is no, waiting for better weather.
But I'm 95% sure the speedo will be almost correct.

Abc> I have found this sprocket, it will take wery little effort to mount up, just a bit expensive considering that you have to modify it first.
http://alienmoto.se/contents/sv/d736.html
154mm cc (Centre to Centre between the mounting holes) 154mm inner diameter.

Sorry i was asking abc but i just wondered as going -1 +2 would throw out the speedo and add milage quicker than what you cover. That on top of a speedo thats already out from the factory.

unless i'm totally wrong?

[robban75]

it uses the front abs sensor for speed readings so it wont matter what you put on

[ktmguy]

it uses the front abs sensor for speed readings so it wont matter what you put on

Spoiler! We could had weeks of fun with that!
It has been explained countless times in the speedo issue tread...

[abc]

looking good nice bit of work.
Abc> I have found this sprocket, it will take wery little effort to mount up, just a bit expensive considering that you have to modify it first.
http://alienmoto.se/contents/sv/d736.html
154mm cc (Centre to Centre between the mounting holes) 154mm inner diameter.

You are right that is expensive. I think I payed $48 aussie dollars for an old stock JT sprocket that had enough material left in the important areas to make the modifications worthwhile. If you find 2D drawings with detailed dimensions for that sprocket or any sprocket for that matter, just post the details and I'll check if it will fit.
It would be nice to find something that requires less work to change up +2

[harold]

I take it you didn't have to lengthen the chain for the 2 tooth larger sprocket?

[robban75]

I will measure it when it arrives this week, if it's good weather tomorrow I am going for a little drive, it's been 4 months since last time

[abc]

I take it you didn't have to lengthen the chain for the 2 tooth larger sprocket?

No change to the standard chain length. Not sure by how much the wheelbase has been shortened as I didnt bother to measure it but the standard method for adjusting the chain tension does the job easily.

[MaximusVR46]

it uses the front abs sensor for speed readings so it wont matter what you put on

ahhhhhh doh

[shadowman]

ABC - Outstanding work!!

When I see somebody with actual skills doing this stuff it encourages me to at least try and do better.

Great work

[abc]

UPDATE:
I have now tested my bike with numerous gear ratios and can report that I have removed the 16 tooth front gear and replaced it with the original 17 tooth front. I have kept the rear at 40 tooth and have found this to be optimum for my type of riding.
Ratios tested so far = (no brake dyno just seat of the pants dyno)
17t front & 38t rear (stock)
16t front & 38 t rear
16t front & 40 t rear
17t front & 40t rear
One thing to note with the modified ratio of 16 tooth front and 40 tooth rear is that although the bike accelerated harder and produced more short punchy wheelies it competed with the traction control too much. Also although the bike was accelerating quicker the length of time the torque curve was active had been reduced. The seat of the pants feeling results in a bike that went like hell but lost the strong pull of the torque. Resulted in heaps of short sharp crazy wheelies but reduced the long and strong midrange wheelies we all love.
My first gearing change was to keep the stock 38t rear and remove the stock front 17t and replace it with a 16t. This obviously made a difference but I felt that even this simple change slightly reduced the "feeling" of strong torque through the midrange. I changed from 16f to 17f and back a number of times in an attempt to find the best mix.
This observation is based on my personal riding on my local roads so I expect others to have a different opinion!
So, I now have 17t front and 40 tooth rear and will leave that ratio fitted. With this arrangement the wheelbase is shorter and the steering quicker. Chain length is just adequate but the rear sprocket must be removed to remove the chain off the front sprocket because there is not enough adjustment at the normal chain tensioning method. If you wanted to fit a 17t front and say a 41t rear you would need a new chain length because you will run out of chain adjustment.
I am not going to get into a theoretical discussion about the characteristics of torque in a V twin and suitable gearbox and final drive ratios but from my observations this final ratio is giving me the best compromise.
Next step is to get my bike onto the dyno so I can take full advantage of all the other mods I have done. Bike still wheelies in 3 and 4th with hand fulls of throttle but I still feel it is necessary to pull fuel from the midrange in the stock Akra map and add a little more fuel up high.

[kevxtx]

Thanks for your feedback well noted, now I need a 40T rear sprocket.

[abc]

Yeh I think the 40t rear is the way to go, I liked it when I went 1 tooth down on the front because it suits australian speed limits etc but I always felt that 1 down on the front was a bit to much and by continuing in that direction with the next logical gear change has shown that it is possible to go too far. If I remember I think it was you Kev that went from 17t to 16t on the front then back and forth a few times until you were convinced! Well I guess I did the same and took the 16t as the best option at the time.
I am glad I built the new 40 tooth rear sprocket and this along with the 17t front will now be my final drive ratio to make the most of this big Vee's mid range torque characteristics.
Enjoy.

[Zei220]

hello, I've been talking to a guy at Talon Engineering and he tells me they can supply a 40t sprocket if we can let them have a sample of a standard sprocket, so, does anyone in the UK have a sprocket laying around? He tells they would only need it for a few days to take measurements. I'd let them have mine, but I'm off touring Germany next week. Costs would be around £40-£50.

Regards,
Dave

[Flipper]

hello, I've been talking to a guy at Talon Engineering and he tells me they can supply a 40t sprocket if we can let them have a sample of a standard sprocket, so, does anyone in the UK have a sprocket laying around? He tells they would only need it for a few days to take measurements. I'd let them have mine, but I'm off touring Germany next week. Costs would be around £40-£50.

Regards,
Dave

Let me know who your contact at Talon is, I'll take the sprocket off mines and send it to him to get things moving on this

Cheers

F.

[Zei220]

hello,

the guys name is Scott Morton, contact number I used was 01935 471508.

Dave

[Zei220]

Hello, thanks to flipper talon are now producing 40th rear sprockets made to order.

You can order on 01935471508, ask for Scott.

[Zei220]

The new sprocket has arrived and is fitted.

https://www.flickr.com/photos/38215980@ ... ed-public/