F800GS 15 Tooth CS Impressions & Questions

[fullmonte]

Originally Posted by Desert Dave

My mileage took an absolute dump, I'm talking like 5 mpg or more. Now I did only test three tank fill ups so far, resetting the MPG computer an checking with a calculator, and there was one really windy section so I'm going to ride more and get more results to make sure that ride wasn't a fluke before I cast judgement.

In my experience, that lower gearing, along with the newfound acceleration that is a byproduct of it, causes the throttle hand to be a bit more enthusiastic than before. Result: increased fuel consumption.

[Desert Dave]

Originally Posted by fullmonte

In my experience, that lower gearing, along with the newfound acceleration that is a byproduct of it, causes the throttle hand to be a bit more enthusiastic than before. Result: increased fuel consumption.

Yes the sportier gearing does cause a hooligan side to appear more often and make the power easier to tap into. Guilty as charged

BUT, that would explain backroad an offroad MPG which stayed closer to normal as the lower gearing often allowed me to smoothly pull a higher gear as often as I whacked open a now torqueier (is that a word ) lower gear. On open highway where it seems the worst I still pretty much hold steady throttle, besides I ride like an old man on the open highway....no sense wasting a ticket on straight road.

[Lucky:)]

Does anybody know torque for front sprocket bolt/nut?

[Bartron]

Just did it today.

25nm

You can find most of the torque values here:

http://f800riders.org/HoW/showentry.php?e=43&catid=5

[Capt.Jim]

Originally Posted by cisco

Sometimes it's hard to out think the design engineer.

Blasphemy! My handlebars and pegs are in the wrong spots, seat is unfit for human use, transmission gearing is all wrong, wheels to soft, engine low on power and the throttle is absolutely to sensitive to any input. All hope is not lost however, we can fix all that BMW has gotten wrong. Now where is that Touratech catalog...

On a slightly more positive note. DD I feel exactly the same as you. 1st is a little to tall and a slightly lower second, even third, would suit me fine on my sandy fire roads.

Is there enough adjustment to pop on a smaller CS cog without changing the chain?

jim

[RobStar]

A 15... you guys have bigger balls than me for sure!

I'm a new rider and found that off-road the 16 was too twitchy in my hands so I upped it to a 17 and am very pleased on and off road. Granted I'm not doing the technical terrain some of you are but for the dirt / gravel roads here around Death Valley and Las Vegas the 17 tamed the beast a bit for me.

My mileage has remained consistent at about 53 - 54 mpg no matter what, where and how I ride it. The 17 helped as well on the freeways as it no longer sounds like the engine is winding out. At 80 mph my rpms are right on the 5000 mark.

RobStar

[cug]

I find the standard gearing just about right for what I do. But I got most of the slack out of the throttle and seem to have better control now. It might just be imagination or wishful thinking but at least it feels better for me.

[Bartron]

Originally Posted by Capt.Jim

Is there enough adjustment to pop on a smaller CS cog without changing the chain?

jim

yessir. you don't even have to loosen the chain to throw the 15 on - marvelous.

[SteveRed]

We will be cracking the ECU of our F800GS project bike and remapping on the dyno for a much more linear and progressive throttle response. What we are hoping for is a very easy and soft throttle without losing any top end. I am doing this with TUNEBOY who offers downloadable tunes from your laptop via a cable. Currently he offers tunes for Triumph and KTM, Ducati etc.

This should take out the snatchy throttle at the very least.

Will keep you posted.

[Lucky:)]

Originally Posted by Bartron

Just did it today.

25nm

You can find most of the torque values here:

http://f800riders.org/HoW/showentry.php?e=43&catid=5

Thanks Bartron

[Lucky:)]

Originally Posted by Desert Dave

So I finally got around to putting on the 15 tooth sprocket (and new chain).

Do you need to change the chain as well when going from 16 to 15?

[Desert Dave]

Originally Posted by Lucky:)

Do you need to change the chain as well when going from 16 to 15?

No, the stock chain would've worked fine, I was a bit skeptical of the quality of the stock chain an had been wanting to upgrade anyway, so this was a good time to do both.

As others have mentioned the stock amount of links works fine. The rear axle will have to move slightly back in order to have the same adjustment with a smaller sprocket, but it was barely noticeable. Removing a link would have moved it quite a bit further forward. I figured I could always pull a link later if I wanted to, but didn't feel any difference at all. Going from a worn chain to a new one will require more axle adjustment then the sprocket did.

[Bartron]

Having had a chance to test the 15 CS off-road on some fairly technical double and single track, I'm impressed. Around the city it's also much more fun in stop and go traffic as it puts the power-band sweet-spots right around the usual speed limits.

Highway travel at 70mph was also not any more of a problem than usual.

I had a chance to work out some of the drive ratios, out of curiosity, for the different set-ups possible.

It's the best $40 CDN mod I've ever made to any motorcycle.

[Keystone]

Where did you get the 15 tooth sprocket? I see one on F800depot, but is it a pretty generic part which I can get from another sprocket company with the right specifications?

Thanks,
Tom

[Bartron]

I got mine from Touratech. They also have a 41, 42 or 47 tooth chainrings available. Hopefully more vendors will have something intermediate, kinda like the 43 available at F800Depot or a 44. 42 to 47's a bit of a stretch.

In other news, does anyone know whether the same drive ration achieved with a 15 or a 16 tooth sprocket will have different torque numbers based purely on the CS or is it the ratio alone that determines the torque change. Not sure if this is clear as written - or just in my head.