2.5L Rocket Stroker Engine Kit with 6 Speed Transmission (R&D)

R-III-R Turbo

Mine is the biggest :)
Oct 12, 2010
2.5L Stroker Rocket III, 04 Hayabusa
Anyone fancy a 2500cc Rocket Stroker Engine Kit?

And/or a 6 speed Rocket transmission?

That is the vision.

Step 1: Build an R&D testing engine from spare parts to run on a bench

This is the construction of the R&D Test engine, which will be used to facilitate & test engine enhancements such as above. It's made from spare parts I've accumulated over the years,, e.g. block fro an 06 Classic, head from a 2010 Roadster, throttles from a silver engine 06 Classic, clocks from a 2013 Roadster, ECU from another 2013, and so on.

Been planning this for a few years now, in fact @warp9.9 may recall some conversations from 2010/11 (before I even had a Rocket) where I was picking his brain about possibility of stroking the engine, and some other stuff.

Original plan was;


Had the spare engine since 2012.. as its first job, it was used to facilitate Carpenterizing my daily driver.
Have been gathering the other spares since to run the R&D engine.

Anyway I did 1 & 2, even though i had the spare engine since 2012 I kinda skipped 3 & 4 and went straight to 5 (except changed mind to supercharger instead of turbo for a few reasons).

I see a lot of folk who would like a 2.5L, 6th gear in their bike (me being one), but nobody has done anything on it afaik.

It's going to be an expensive venture, it will take a LOT of time.
I'm prepared to go through with it just so I can have it, and if anyone else wants a kit too (once R&D is complete and the kit is proven and solid / after I've done the guinea pig duties..) that would also be welcome.

The plan would be to have multiple trims of the kit available too - you could go for same materials that are in the stock engine, you could go for high end/light/stronger metal if you're a power maniac, you could go for low compression ratio (8:1) if you want to go boost, or you could go for high compression ratio (~12:1), same goes for the tranny, you can go basic material or full on high end indestructible material.

I don't know if the 6 speed is possible in this block - we will see. Might have to go another route that's thinking outside the box :)

On Roadsters at least the GPS has a 6th gear position already on it. I found this 6th gear the time my GPS went faulty. Getting 6 gear maps made from Dynojet for map-by-gear ain't a problem.

But I believe it is entirely achievable to move up to 2.5L... that's not much to ask.
i hope it can all be done just with stroker crank, rods etc. But if we also need to bore out the cylinders and fit thinner liners made from stronger metal and fill them with different pistons.. well so be it.

The Rocket cylinders are 765cc each, with a diameter of 101.6mm and stroke of 94.3mm (an oversquare motor). If we increase stroke length (that's what she said) to 101.6mm to be perfectly square, the engine CC will rise to 2,472cc (or 2.5L :D).

If we go all the way to 2499cc, stroke length would need to be 102.7mm, an undersquare motor.

Reckon there will be a downside to the stroker though - higher piston speed for the same revs as stock engine. This might limit us in terms of top engine speed - the 9000rpm redline mightn't work, might need to limit to 8, 7 or even 6k rpm. But the torque increase/lower down and increased fuel economy might be worth it for some..

Thinking the kit would look like:
> Stroker crank
> Matching balancer shaft
> Journals, bolts, wrist pin circlips etc etc
> Stroker conrods
> TuneBoy & TuneECU maps
> OEM-looking 2500cc badges to replace the 2300cc ones
> Pistons if needed

Step 2: Get R&D engine running

Almost there, got a couple of faults to fix;


Step 3: Measure up engine & transmission internals

Step 4: Design new components

Step 5: Get new components made

Step 6: Install & trial new components......

Anywho, been dying to get stuck into this for years,,,, so here I go :)


Staff member
Aug 3, 2014
Fairfax, Virginia
Triumph: 2014 Rocket III Touring
I should add, that I'm more (much) interested in the 6th speed -- along with ample interest expressed on this site for ten years or more (and would love to see you prove the naysayers wrong -- reminds me of the adage 'Those who say it can't be done should step aside for the ones doing it.').

Oh, and your R&D would have to include an understated badge of some sort akin to the letters on Mercedes and BMWs that give a clue to the vehicles salient characteristics.


Aspiring Student
Jul 25, 2014
Olympia Washington
'14 R3R, '02 Daytona 955i
You sir, need to move closer to me, like next door, so we can combine our powers and form Captain Rocket 3!!

I'm too exhaust to consume technical stuff atm, 1200 miles on my sportbike, all twistie roads, has absolutely wiped me out, but, I'll revisit soon!

I have done some research along exactly these lines already and sources some shops that have confirmed they're both able and willing to take some of the work on.
AdBlock Detected

We get it, advertisements are annoying!

Ad-blocking software does a great job at blocking ads, but it also blocks some useful and important features of R3Owners. For the best possible site experience please take a moment to disable your AdBlocker for R3Owners.Net.

I've Disabled AdBlock