Why gear down or up?

**baffa** · 2nd March 2012, 14:56

I notice a few people change the rear sprocket and gearing on their bikes. How common is it? And why?

I can see the appeal on a sports bike, enjoying the sweet sweet sound of an IL4 at redline is only possible at insane speeds. Apolagies to anyone who was woken up last night on a certain street on the shore, the throttle jammed I promise

**wanpo** · 2nd March 2012, 15:03

Originally Posted by baffa

I notice a few people change the rear sprocket and gearing on their bikes. How common is it? And why?

I can see the appeal on a sports bike, enjoying the sweet sweet sound of an IL4 at redline is only possible at insane speeds. Apolagies to anyone who was woken up last night on a certain street on the shore, the throttle jammed I promise

Longer gears for fuel efficiency (lower revs = less petrol burned)

Shorter for acceleration, stunting, overcome lack of torque.

I imagine people big into racing would change (possibly either way) to escape being inbetween the sweet spots of two gears when you want to get on the gas mid-corner. (You want to be in the torque to get the drive out)

**george formby** · 2nd March 2012, 15:10

Standard gearing on tubby is 3800rpm @ 100kmh. The engine is not quite in it's sweet spot. 1 tooth down on the front is 4000 rpm (ish) @ 100 kmh. Right on the money stroke, more responsive, smoother & more fuel efficient. Smaller throttle opening for the same revs. That's my reason any hoo. It also means I can ride between 15 & 100+ kmh in third if I so desire, very handy on twisty roads.

**SMOKEU** · 2nd March 2012, 15:25

I went -1 on the front because the bike needs the shit revved out of it to go anywhere fast and has a big torque hole below about 4,000RPM due to the jetting.

**george formby** · 2nd March 2012, 15:32

Originally Posted by SMOKEU

I went -1 on the front because the bike needs the shit revved out of it to go anywhere fast and has a big torque hole below about 4,000RPM due to the jetting.

Jetted for performance or to get through noise emission regulations? My bike gets happy just above 4000rpm on standard jetting. A lot of bikes seem to have an ole about there in the rev range.

**DEATH_INC.** · 2nd March 2012, 15:36

-1 +1 on the 10. Makes it accelerate quicker. 170kph in first is a bit silly, tho it'll still do 160+. Makes it silly trying to keep the front tyre in contact with the road tho

**javawocky** · 2nd March 2012, 15:38

Originally Posted by baffa

I notice a few people change the rear sprocket and gearing on their bikes. How common is it? And why?

I can see the appeal on a sports bike, enjoying the sweet sweet sound of an IL4 at redline is only possible at insane speeds. Apolagies to anyone who was woken up last night on a certain street on the shore, the throttle jammed I promise

I have never changed gearing but I can understand why someone would on the track.

Hampton Downs Turn 4 (The 90 slow right hander) up the hill towards the left hair pin. Second gear is just about perfect to give enough drive off the corner and closer to red line before the braking spot. I think If I were a faster rider I might adjust gearing a little to avoid a gear change.

Which reminds me how much I love an IL4 which a large rev range

**george formby** · 2nd March 2012, 15:39

Originally Posted by DEATH_INC.

-1 +1 on the 10. Makes it accelerate quicker. 170kph in first is a bit silly, tho it'll still do 160+. Makes it silly trying to keep the front tyre in contact with the road tho

Ahh, to save money on tires?

**Kickaha** · 2nd March 2012, 15:42

Originally Posted by SMOKEU

and has a big torque hole below about 4,000RPM due to the jetting.

Then why don't you get it jetted correctly?

**SMOKEU** · 2nd March 2012, 16:00

Originally Posted by george formby

Jetted for performance or to get through noise emission regulations? My bike gets happy just above 4000rpm on standard jetting. A lot of bikes seem to have an ole about there in the rev range.

Apparently it has a Yoshi MJN jet kit in it. The guys at the gixxer.com forums seem to think so as well from the description I've given them. I know it's not jetted to give low emissions as it does around 8L/100km on the open road when I'm not riding too hard. It's a 600 SRAD.

Originally Posted by Kickaha

Then why don't you get it jetted correctly?

As above.

**Kickaha** · 2nd March 2012, 16:10

Originally Posted by SMOKEU

Apparently it has a Yoshi MJN jet kit in it.

That doesn't mean it's right

Originally Posted by SMOKEU

The guys at the gixxer.com forums seem to think so as well from the description I've given them.

Have any of them tried running one on a dyno to check one properly?

**SMOKEU** · 2nd March 2012, 16:24

Originally Posted by Kickaha

Have any of them tried running one on a dyno to check one properly?

I'm not too sure. I'm not really that worried about it because it runs very well if I keep the revs above 4,000RPM, just gets fairly jerky and rough and feels like it's running rich at low revs. Still, better rich than lean.

Carbies have recently been stripped and balanced by a bike shop as well.

**nzvlogger** · 2nd March 2012, 19:33

Very helpfull going down 1 tooth on the front for a VFR400, itl do 120km in first standard but you got to ride the clutch with the standard cog at the lights. makes them feel much better low down.

**GrayWolf** · 2nd March 2012, 23:12

Originally Posted by SMOKEU

I went -1 on the front because the bike needs the shit revved out of it to go anywhere fast and has a big torque hole below about 14,000RPM due to the jetting.

there, fixed it for you