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Offline Kamboskid

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changing cogs, front or back
« on: 06 August, 2019, 09:55:07 PM »
 Hi, know this has been raised before, curious to hear different opinions on this issue. I feel the biffer is under geared, I can pull away in any gear, seems like it needs another gear, I live on a Greek island and the bike is just right for those roads, plenty of low down torque pulling along in high gears and low revs.
However, I feel the urge to tour and that means motorways, autostradas and autobahns, will changing the front spocket make a better touring bike and hopefully increase fuel economy or am I missing something?

Offline raYzerman

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Re: changing cogs, front or back
« Reply #1 on: 07 August, 2019, 01:49:29 PM »
It boils down to how you're going to like first gear after switching up the gearing....... start perhaps by changing the front sprocket to one more tooth up.  Common thing to do on lots of bikes.  This is a minor change.  You can change the rear sprocket to something, but at some point you'll run out of chain and need a longer one.  I'm a newbie to the Biffer and kinda sorta feel the same way, and at some point will swap out the front sprocket.  I'm not sure what others have found by doing sprocket changes on Biffers.
« Last Edit: 07 August, 2019, 01:52:50 PM by raYzerman »

Offline Art

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Re: changing cogs, front or back
« Reply #2 on: 07 August, 2019, 04:27:51 PM »
I looked at this a while back and the popular options are plus 1 tooth on the front sprocket vs minus 2 teeth on the rear sprocket. The final reduction ratios for comparison purposes are

standard 16 tooth front and standard 43 tooth rear sprockets gives a ratio of 2.69
+1 tooth 17 front and standard 43 tooth rear sprockets gives a ratio of 2.53
standard 16 tooth front and -2 tooth 41 tooth rear sprockets gives a ratio of 2.56

Wemoto prices are - JT front sprocket plus 1 tooth £22.85 and JT rear sprocket less 2 teeth £23.76, with both jobs taking  more or less the same amount of time and effort there's little in it. The only difference I can see is that the plus 1 tooth front sprocket will have less impact on the chain slider than a minus 2 tooth rear sprocket. Either modification will improve the accuracy of the speedo. A reliable source tells me on average the conversion will pay for itself in fuel economy after 4,000 miles. I've heard Power Rangers talking about the weight saving gains in having a smaller rear sprocket and being able to run a shorter chain length. The concern I have is the extra physical space required around a larger front sprocket, since others on here appear to have successfully carried out the 17 tooth front sprocket modification without comment I don't anticipate this to be an issue. For me its more about not looking for that 7th gear although the correction to the speedo and fuel economy would be a bonus.

I don't think this one is worth pursuing without cause so I'll be leaving mine until the sprocket and chain replacement. At which time I'll opt for the plus one 17 tooth front sprocket, standard 43 tooth rear sprocket and standard 120 link chain which should fit with either modification although it is likely to put the chain wear indicators out by some.

Offline Tommo2

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Re: changing cogs, front or back
« Reply #3 on: 07 August, 2019, 04:36:59 PM »
Like you Kamboskid, I felt the bike was under geared and revved needlessly, almost twist and go scooter-like. As you say there is stuff elsewhere on this on the Forum. I went one tooth up on the front sprocket, again there are excellent instructions on this Forum of how to do it. I am much happier with this arrangement. I find the engine revs about 500 revs less for the same speed in top gear. I have checked the speedo and as already mentioned, the speedo is far more accurate. (I checked it against GPS). There is so much power it makes little difference geared up or standard, a slight twist of the wrist may be the difference. It works for me, and I would recommend it. It costs little to do, and you can always change back to original if you don't like it.

Offline raYzerman

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Re: changing cogs, front or back
« Reply #4 on: 07 August, 2019, 05:03:44 PM »
I was in error in my statement about the rear... Less teeth on the rear instead of More... would need shorter chain as Art clarified. 
Thanks for the real world info Tommo, makes me want to go with the 17 tooth sprocket........
Good info all!!
« Last Edit: 07 August, 2019, 05:09:06 PM by raYzerman »

Offline raYzerman

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Re: changing cogs, front or back
« Reply #5 on: 07 August, 2019, 05:05:43 PM »
Deleted (dupe).
« Last Edit: 07 August, 2019, 05:07:35 PM by raYzerman »

Offline Westoneboy

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Re: changing cogs, front or back
« Reply #6 on: 07 August, 2019, 05:49:17 PM »
I can see the idea behind changing the gearing but would it not suffer on acceleration ie for overtaking. I feel it is slow enough
Compared to other bikes without reducing it more. I am kicking down at least two gears to overtake at present but if changed the gearing as suggested I would probably be kicking down 3 to overtake from about 50mph.I suppose you could change it pre tour and change it back again for every day use.Just my opinion.

Offline Rev Ken

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Re: changing cogs, front or back
« Reply #7 on: 07 August, 2019, 07:32:47 PM »
*Originally Posted by Westoneboy [+]
I can see the idea behind changing the gearing but would it not suffer on acceleration ie for overtaking. I feel it is slow enough
Compared to other bikes without reducing it more. I am kicking down at least two gears to overtake at present but if changed the gearing as suggested I would probably be kicking down 3 to overtake from about 50mph.I suppose you could change it pre tour and change it back again for every day use.Just my opinion.
I found the torque in almost any gear and speed plenty enough to overtake - unless I was pushing my safety margins. My BMW F800GT does need to drop a couple of gears as it doesn't have the same spread of torque and is higher geared - something I had to get used to as I tended to stall when moving off. Interestingly It pulls the same revs in 5th gear as my CBF in top.
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Offline Westoneboy

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Re: changing cogs, front or back
« Reply #8 on: 07 August, 2019, 10:19:15 PM »
Maybe it's because I have riden a blackbird for the last 14 years . I do love my CBF but it is slow on the overtake  compared to most 1 litre machines but if fast enough for you fare comment.

Offline Rev Ken

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Re: changing cogs, front or back
« Reply #9 on: 08 August, 2019, 07:47:54 PM »
*Originally Posted by Westoneboy [+]
Maybe it's because I have riden a blackbird for the last 14 years . I do love my CBF but it is slow on the overtake  compared to most 1 litre machines but if fast enough for you fare comment.
I now understand! My son has a (Tuned!) Blackbird and now has my CBF1000 which he refers to as his 'moped'. However it is ridden a lot more than the Blackbird, and often two up, something the Blackbird isn't as practical. Horses for courses! :031:
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