6-speed box in GSXR1100 - good or bad?

[Jonny]

I was planning to put a GSXR750 6-speed box in an 1100 motor that I’m going to be building for my Harris project.
 

However I have been told that people who have done this were not happy with how the gearbox worked with the engine. 
 

Has anyone got any feedback on whether it’s worthwhile doing? I want to do it because I think it will give me a bit more flexibility on the twisties.

[Gixer1460]

Can't speak of any experience but with a sorted 11 you are never really in the 'wrong' gear, the torque negates 'stiring the box'. Personally i'd fit well tuned flatslide carbs with their immediate response to work the torque. Also, seeing how often the 2nd gear cluster gets destroyed / worn out, i'd be wary about slimming all of the gears to accomodate the extra one!

[clivegto]

There used to be a site member that fitted 6 speed boxes to his 1127 TT race bikes on hear but unfortunately he got banned for sumat. I haven't done this conversion but always fancied try it as Mr Gixer1460 says there isn't any real advantage with the bigger cc motor unless it's running a flowed head with high lift cams then when going round and round a racetrack you could keep it on the buzz all the time. 

[TLRS]

From a performance perspective it might not make a lot of sense. But some people like an angry bike you have to feed gears quickly. Perhaps with a shorter final ratio.. it'll give mahoosive shove everywhere. And still keep some decent revs at motorway cruise speed.

[spiderpig]

Was a Dutch member I think on here running a 1216 track bike with 6 speed without any issues.

 

If you've deep pockets Nova do a close ratio 6 speed box for the 12

[Nik]

Good! My input and some more info here 

 

[wraith]

Haven't done it, but I'm thinking of went the output bearing goes on my 1100 engine, hopefully not for a long time 

From what I've read up to now, you have to do some work on the crack cases for the gear box bearings to fit and you need to look at the clutch.

Up side is revs quicker in the first 3 gears, down side you will need to change gear quicker.

Top two gears have the same gearing as the 1100 so motorway riding not a reving problem. 

This is what I've read mostly on these pages over the years

[Jonny]

On 5/21/2026 at 8:06 AM, Nik said:

Good! My input and some more info here 

 

Thanks for posting this Nik, I hadn’t seen this. Think I probably will have a go!

Edited May 26 by Jonny

[wraith]

So just to confirm, the DOT head gear box will not fit the gsxr1100 1127cc engine?

[Gixer1460]

3 hours ago, wraith said:

So just to confirm, the DOT head gear box will not fit the gsxr1100 1127cc engine?

It will - just not directly without minor modifications. Its not a drop in and ride deal.

[wraith]

27 minutes ago, Gixer1460 said:

It will - just not directly without minor modifications. Its not a drop in and ride deal.

I remember someone saying you need to alter bearings, but that might of been with a b12 engine  the grey matter is not as good as it was 

[dupersunc]

Bit of faffing with output shaft bearings and clutches.  Not worth it for the road really, but on track the 1100 gearbox ratio splits are very poor. Lower gears 1.2.3 are too close, and higher gears 3.4.5 are too far apart.

[Ted M]

I’ve not ridden mine yet so I can’t comment on what it’s like to ride but I have just fitted a teapot 750 box to a bandit engine. It’s not as straight forward as you may think. I did it because I had one and I always wanted to try it. 
I did some research on this and the Nova box are the same ratios as the GSXR 750 slingshot. The difference between the teapot and GSXR slingshot boxes is that 1st gear is 1 tooth bigger on the teapot output shaft. Because of this you will need to smooth out some of the engine case. 
The clutch is the pain in the arse you need the GSXR 1100 basket the model that uses coiled springs not the diaphragm spring and not the Slabby basket. 6th gear on the 6 speed box is slightly lower that the 11/1200 box due to the different number of crank/clutch gear teeth. Have a look at my project thread “The Longest Day Challenge” I’ve written up the build for the gearbox. 

Edited June 15 by Ted M
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