Another thread about chain and sprocket, this time for efficiency!

[embee]

I too run a 16T on a curvey SVS. Th emain reason I went to it was because I always felt 6th was subjectively too low and I often looked for 7th (but this is a personal thing having been used to lower revving bigger twins).

It feels much more natural to me out on the open road and on motorways, and I can't ever remember searching for that elusive 7th gear since.

Economy? I reckon Graman's about spot on, 2 or 3% is the ballpark, whether you'd really notice that is debatable, it's maybe 1mpg, but it's likely to be in the right direction.

I'd say do it just for the more relaxed feel. I've often wondered what a 17T would feel like, unfortunately I'd need a longer chain to do it so haven't bothered, the 16T goes in with the stock chain length (curvey SVS).

Id like a more relaxed ride on the motorways too, but i dont think id be happy sacrificing my acceleration, i need two bikes lol.

Embee is right about the standard gearing. It feels too revy when cruising. I have used a gearing spreadsheet to check the change in rpm at various speeds:-
The standard gearing 15t, = 14.1mph per 1000rpm
16t = 15 mph per 1000rpm
17t = 16 mph per 1000rpm

So at 70mph, standard 15t = 5000 rpm
16t = 4700 rpm
17t = 4400 rpm
You can see that it drops the rpm significantly. I run a NTV 650 as well which has 15mph / 1000rpm which is the same as the 16t gearing so I knew that the SV with more power, lighter and better aerodynamics than the NTV, it could pull a taller gear. It does and feels like a much larger engined bike with the engine spinning slowly.

This helps to get my economy to average at least 80mpg. (Not a misprint)

80mpg average is a tall ask... average I assume to be across every entry in a log book. I got pretty decent mileage out of the SV and even copped a little flack for it, but it was nowhere near an 80mpg average.

...............



For a bike that spends its days on motorways, a 16T counter shaft sprocket might be just the shot. However, if the bike spends the majority of its days running around at lower speeds in traffic then I'd suggest going the other way to better match load, rpm and road speed to the dominant conditions even to the point of gaining one full gear at those speeds. ie using 4-5 instead of 3-4 as the main cruising gear at lower speeds. Another benefit is that it is a lot easier on the clutch and oil plus it makes low speed manoeuvring a little easier.

There is some guy on this forum, but can't remember who he is, who runs what sounds like silly gearing. It is not so silly around town because it enables the full use of the gearbox and possibly a better load/rpm/speed match across this range of road speeds... if he were inclined to settle down.

Thanks for the comments, it's defiantly sounds like it would work out for me, but I don't think it's worth changing my current set up prematurely.

[kaivalagi]

3% better efficiency increase on going up one tooth on the front doesn't sound worth the hassle for efficiency alone.

Why not just change your riding style a little and be more progressive with the throttle and take it easy?

Also, does changing the number of tooth affect the speedo? is it based on the front sprocket or wheel or what?

[yorkie_chris]

Speedo is driven on front wheel.

3% is not a lot but when you are doing what that guy above is doing and making lots of little changes and all of a sudden is getting 80mpg it is worth it.
That is no-sh*t DOUBLE the mileage I get.

I'm considering going completely back the other way with all my tuning mods. Milder cams, taller gearing.

[kaivalagi]

Originally Posted by yorkie_chris

Speedo is driven on front wheel.

Good to know I can slap a 14tooth cog on there no worries, I don't need the top end and like has already been said going 4th-5th rather than 3rd-4th alot might actually be beneficial in some small way

Originally Posted by yorkie_chris

3% is not a lot but when you are doing what that guy above is doing and making lots of little changes and all of a sudden is getting 80mpg it is worth it.
That is no-sh*t DOUBLE the mileage I get.

I get anything from 45 to 60mpg, higher for long runs, lower for evening/weekend blips...I just don't believe 80mpg, 70mpg maybe at a push but not 80mpg...surely not.
I've also been messing about with my riding style too and I reckon could get to 65mpg without mods if I could control myself all the time.

Originally Posted by yorkie_chris

I'm considering going completely back the other way with all my tuning mods. Milder cams, taller gearing.

If you do please journal it so we have something from beginning to end to follow and whole heartily believe

If 80mpg is totally genuine then I salute the poster, I just find it very hard to beleive...and need proof to go with it 100%

To get a good mileage you need to record the amount of petrol you put in the tank and mileage and ideally put it into a spreadsheet so it can calculate the last average mpg and the total mpg. Now you have a base for checking data.

My runs are at consistent speeds on dual carriageways and do 30 miles with only one roundabout so there is hardly any accelerating or braking. Any vehicle is economical doing this as long as you do not go fast (over 60mph) as the aerodynamics rob the efficiency. (drag is proportional to the speed squared).

I have logged the fuel consumption for 25000 miles and always have achieved over 80mpg commuting. Before I used it for commuting I still got over 60mpg. I enclose a graph from the spreadsheet.

http://forums.sv650.org/attachment.p...7&d=1291575586
Graman

[Stu]

30 miles without exceeding 60? Yup, cos that's going to happen.