Any tips for extra economy?

[Gidanski]

Was just about to get my NC31 back on the road again and was wondering if anyone had any major tips for making mods for better fuel economy?

Before it got smashed up it was getting roughly 4.2l/100km (61mpg?) and that was on the stock 15-45 sprockets and 2 and 7/8ths on the idle mix screws as well as a K&N and a DIC Alloy can.

Now it has 16-37 sprockets, Dan Moto System and was thinking of dropping back to 2 and 1/4 turns on idle as well as changing to colder plugs. My thinking is the leaner mix will be hotter and as a result will cause hotter plug temps thus needing a 1 heat range colder plug so as not to burn them. Thinking CR9EIX-11 NGK's or similar, as apparently the service life of the iridiums is 60,000km+

Also tyre pressures. Do I just run the normal 36 or do I bump them up to 38?

And finally would fitting a Headlight cowl help as well? Eg Aero gains.

[superv500]

I'd have liked to have seen some peoples opinions on here of the mods you're planning to do.

There is another thread going about fuel economy at the moment, so perhaps have a look there as well?

61mpg is pretty good for a revvy 400. If you want economy then try the CB500 twin...

[amorti]

61mpg is already excellent from a carb-fed 400. Even the 500 twin won't get much better than that.

If you reduce the revs you don't always necessarily reduce the fuel consumption, the engine could be working harder at lower revs / labouring.

A full fairing might help a little bit especially if (judging by the mpg you're getting) you spend much time cruising on faster roads. A windscreen fairing won't make much odds but will make it more comfy at highway speeds.

You could just about hope for 80mpg from a new Fi CB500 or a G650GS single. Neither will be faster than your 400 nor more fun. However unless your doing a LOT of miles, you might as well stick with the cheaper bike and consider total costs.

[vr46]

36PSI tyre pressure? that seems way too high. None of my bikes run pressure that hard.

[Gidanski]

The sticker I have on the swingarm says 260/260kpa for front and rear tyre pressures without pillion, Which is roughly 37psi. With pillion it wants 280/280. And it is the factory sticker too.

[Mansie]

... and that was on the stock 15-45 sprockets ...

Now it has 16-37 sprockets...

Wow, that is a radical change! Can you describe how the bike feels with the new sprocket set-up? Any issues accelerating? What are the revs at 60 mph?

[Gidanski]

16-37 felt unsafe to me when pulling out onto highways and stuff. Also had to be brutal with the clutch to get it to move.

Ended up putting the 15 tooth back on and is a lot better now. Bike actually wants to move off the line. Its sort of like having an extra gear, first seems like 2nd used to be. In 6th you will sit at roughly 4500rpm at 100kph, as opposed to the 7000 it used to do. Still a little droneish but no where as bad as it used to be. Can get off the bike and still be able to hear, BTW I have a really loud exhaust, even with the baffle in. Neighbors love me.

Can still do over 110kph in 2nd though.

[Mansie]

Thanks for the quick reply!
The standard for the CB400 NC36 is 15-42. I have been using 15-40 but the revs at 60 mph are still at ~6000. I thought I just give 15-37 a try. I don't have 6th gear so I expect the get around ~5000 revs at 60 mph. Will see how driving off goes.

I think the fuel economy that you achieved on your bike of ~60 mpg is be already pretty good. Do you have any information how much benefit the other modifications have given you?

I used to run a Yamaha YBR 125 and that did >100 mpg. My neighbour used to have a YBR 250 and he reported ~80 mpg. Anyway, the new batch of 250cc bikes are the ones to look into if you are after good fuel economy.

[jolly]

Was just about to get my NC31 back on the road again and was wondering if anyone had any major tips for making mods for better fuel economy?

Before it got smashed up it was getting roughly 4.2l/100km (61mpg?) and that was on the stock 15-45 sprockets and 2 and 7/8ths on the idle mix screws as well as a K&N and a DIC Alloy can.

Now it has 16-37 sprockets, Dan Moto System and was thinking of dropping back to 2 and 1/4 turns on idle as well as changing to colder plugs. My thinking is the leaner mix will be hotter and as a result will cause hotter plug temps thus needing a 1 heat range colder plug so as not to burn them. Thinking CR9EIX-11 NGK's or similar, as apparently the service life of the iridiums is 60,000km+

Also tyre pressures. Do I just run the normal 36 or do I bump them up to 38?

And finally would fitting a Headlight cowl help as well? Eg Aero gains.

15/36 superfour revs lower about 1200rpm then standard 15/42 set up

[Gidanski]

Just a quick update on the bike. Finally seemed to have got the tune sorted on it so its not bogging down or sounding like its having fuel dumped in it. Altitude is roughly 80-100m above sea level for most of my riding, temps when tested were roughly 26 degrees C.


Carb settings are as follows:
2.0 Turns out on Idle mixes, ~1100 rpm Idle speed
105 Main Jets on all 4 carbs ( Not sure of brand, non genuine Keihin though )
Stock Needles with shims removed (Assuming they are stock...)

Exhaust:
Danmoto Carbon GP with dB baffle installed


Tested it tonight and it seemed to pick up a lot better down low and seemed to pick up speed nicely. Wasnt having to use as much throttle to get it moving. Also sounded a lot quieter. Did not get harassed by friends neighbours when I pulled up as well (Was roughly 8pm when I got there and neighbours hate my bike for some reason )

Will post results of economy after the next few tanks ( May be a week or so )