Gearing

[metalforever]

I'm wondering what the general thoughts of the divvy's gearing is?

Is the standard gearing a good ratio or could it be improved?

The reason I ask is i'm considering increasing the size of the front sprocket, not necceserily for more top speed but to get the revs lower down when cruising around. I quite like silly acceleration offered by a bike but im sure 1 tooth up wont reduce this too much.

The other reason is i'd like a slightly better fuel economy, not having a working reserve puts me off trying to find how many miles till empty i can do but after spirited riding i appear to be getting about 50+MPG.

I'd like to try and bring this nearer 55-60 if i can hold back on the throttle openings.

Any advice or reccomendations with regards to divvy 6 gearing?

[amorti]

Mine was -3 (or 4 even, I forget?) on the rear when I got it, which is about equivalent to what you are suggesting.

I would say don't bother. The bike was noticably slower off the mark, it won't go any much quicker at the top end as it's limited by power and aerodynamics before it's limited by running out of revs. I would say the extra 2-3 mpg are really not worth it.

50-55 mpg is pretty normal for these bikes, I gather. TBH that's some very good numbers and you have a big enough tank for about 165-175 to reserve, and a good further 30 miles. I've even filled up at 220 before now.

You'd probably be better off spending the money of a new sprocket on a new air filter, that might give an extra mpg or two on its own. Why not check if (particularly in summer) you can knock the idle down 100 rpm? It's not much but won't hurt miles per tank. Are your brakes dragging at all? That costs fuel. All possibilities for the tight eco-friendly, frugal rider amongst us

Edit - also, try taking the fuel tap out and having a look at it. I would bet it's just a failed O-ring that's causing the reserve tank not to operate. I'd hate to find out I had a fuel leak, or had forgotten to brim it last fill, or my bike had suddenly got worse consumption figures by virtue of running out of fuel on the motorway.

[metalforever]

cheers, ive had the fuel tap apart and i cant find anything wrong with it to be honest, its been kept in perfect condition so there is no wear on these parts. my reserve fails to old fuel which is my problem, its not leaking just when the tap is on it will drain reserve also.

Nevermind!

Thanks for the gearing experience info too, ill leave it alone, afterall reduces potential acceleration could cause problems should you need a sudden burst!

[CD]

Way back I built a kit car using Ford Escort MkI and MkII running gear. My car had larger wheels so I fitted the lowest ratio differential used on cars. I later fitted an overdrive gearbox to give me 5th gear (sort of) and the fuel consumption got worse. The engine was being overgeared so I fitted the ultra low ratio diff from an Escort van and overdrive became slightly higher than the original top (4th) gear. The fuel consumption was now the best ever. The right gearing is a must-do to get the best performance and fuel usage.

The D600 gearing will be a compromise but Yamaha will have gone to lots of trouble to get it right. The 600 is spinning quite fast at M-way speeds, but its built to do that and D600s are not known for engines wearing out at low miles.

I would leave it alone.

[bobh]

The N has lower gearing than the faired bike, with an extra 2 teeth on the back (48 c/w 46, I think), presumably because it has more wind resistance and a lower top speed. Even then it's not particularly lively compared with other 600's.

The only reason I can see for raising the gearing substantially is to make the lower gears a bit longer - they always seem too low to me. But if you did that you'd have to treat it as a 5 speed box with overdrive.

One positive thing about the lower gearing on the N is that at 60 mph cruising in 6th the engine is just above the 4-4.5K rpm vibration period. Not much help if you're in the Peak District, though - I was up there at the weekend and every decent road seems to have a 50 limit now.

[CD]

Forgot to mention. I have a 1977 Suzuki GT750 with what I believe is standard gearing. 5th is all but useless as it seriously overgears the bike. 1st is also much too tall and even 2nd is quite high. The chain set is quite new but when it does (eventually) get back on the road, sprockets for a lower gearing will be must-h.aves

[Swim41]

Jul 28, 2009 18:09:11 GMT bobh said:

The N has lower gearing than the faired bike, with an extra 2 teeth on the back (48 c/w 46, I think), presumably because it has more wind resistance and a lower top speed. Even then it's not particularly lively compared with other 600's

Sorry to butt in, but when I had my C&S changed recently on my XJ600N I was quoted quite a bit more for '600N' sprockets than those for an '600S', so I said to go with the 'S' arrangement.

Doesn't seem to make much difference but in theory will my fuel consumption be improved or worsened?

[CD]

I would guess that unless you really work hard to be gentle on the throttle when cruising and always change down for accelerating the fuel consumption could be worse with over-high gears. Keeping an engine spinning on low throttle doesnt seem to spoil its fuel consumption.

Any engine has valve timing to suit the revs it's normally expected to do. Running a (relatively) high revver in a high gear saves a bit on friction losses, but because the valve overlaps are set for higher revs the pumping losses go up. Probably lose more than you gain.

[HRHpenfold]

try this site out,

www.gearingcommander.com/