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

[Donny Coveney]

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 ).

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

I've had a few ideas lately which comes with a few questions you might be able to help with..is the later 2500cc engine able to be a straight swap with a 2300cc engine?
if so will the earlier crank interchangeable into the later engine?
Heads also?
So if I was to get hold of a later bottom end and put my 2004 crank, head cams etc..then I would have a big bore engine..2.6 or 2.700cc or better..
What do yous think???

 

[R-III-R Turbo]

I've had a few ideas lately which comes with a few questions you might be able to help with..is the later 2500cc engine able to be a straight swap with a 2300cc engine?
if so will the earlier crank interchangeable into the later engine?
Heads also?
So if I was to get hold of a later bottom end and put my 2004 crank, head cams etc..then I would have a big bore engine..2.6 or 2.700cc or better..
What do yous think???

Simple answer, no.

I could be here all day outlining reasons why not, but in summary they are two completely different engines.
One might as well be asking if the crank from a BMW i8 will fit.

Good news is you should indeed be able turn your 2004 from a 2.3L into a 2.6 or 2.7L maybe.
You would need to pop in a Stroker kit, which will bring you up to 2.5L, and then fit larger bore custom made pistons and cylinder liners.
The larger bore will bring you up to maybe 2.6 or 2.7L I think I calculated previously, it won't be much as there is only so much meat on the stock liner thicknesses that could be removed without adverse impact.

To my knowledge a bored out Rocket III has not been done, but the Stroker has, that's well documented here.

 

[SDR_11 Rocket]

Calculations done a while back indicated ~27% reduction in engine RPM while maintaining the same road speed, going into 6th from 5th.
As in ~2200rpm down from ~3000rpm, at ~80mph.

The only practical means available so far is the 3D printed plastic gears in the video, where the input speed is ~73% of the output speed, so this initial practical test is consistent with the calculations.

I forgot the laser tachometer so RPMs are just from counting revs (blue tape!) per second by stepping through the footage frame by frame in a video editor program. That and the transmission was being spun with a handheld battery drill, so the input speed could vary slightly.
Hence the "approximate" RPMs and %'s!





The plan is - if it works and is reliable, that is - to make the kit available in 2 levels of "trim";

(1) Standard 6th gear kit - base kit of what's needed to have the 6th gear

(2) Premium 6th gear kit - Complete Transmission Upgrade - includes undercut dogs, deepened & widened circlips, billet replacements for the weaker gears, improved dog meshing from a selector drum upgrade, and also comes with all the OEM/Triumph consumables like gaskets, oil, circlips etc needed to do the upgrade.

What would it have cost all in to have the 28 gear sets manufactured ? ( I believe that was the minimum order you had stated in one of your postings )

 

[R-III-R Turbo]

Oh I would have to check my detailed files but from memory it was something mad like €20K for a once off set.
And it would have taken like 20 sets or thereabouts to bring the cost per set down to a 'reasonable' e.g. €2K region

 

[SDR_11 Rocket]

Simple answer, no.

I could be here all day outlining reasons why not, but in summary they are two completely different engines.
One might as well be asking if the crank from a BMW i8 will fit.

Good news is you should indeed be able turn your 2004 from a 2.3L into a 2.6 or 2.7L maybe.
You would need to pop in a Stroker kit, which will bring you up to 2.5L, and then fit larger bore custom made pistons and cylinder liners.
The larger bore will bring you up to maybe 2.6 or 2.7L I think I calculated previously, it won't be much as there is only so much meat on the stock liner thicknesses that could be removed without adverse impact.

To my knowledge a bored out Rocket III has not been done, but the Stroker has, that's well documented here.

 

[SDR_11 Rocket]

Oh I would have to check my detailed files but from memory it was something mad like €20K for a once off set.
And it would have taken like 20 sets or thereabouts to bring the cost per set down to a 'reasonable' e.g. €2K region

So it sounds like 40,000 all in for 20 at it s best. I wonder if it would be more inexpensive in the states . I do have machine shops in my area in Pennsylvania ( Lancaster Country is full of trades people ) . Now that the bikes are getting older I dont know if there is the interest at this point but I know I am interested. If I had approximate specifications ( I realize you may not want to share all the details ) but if I had approximate dimensions and gear cut style etc .I could take that information and stop in a couple shops and see what they would have to say. A little bio I am a auto and heavy equipment mechanic. I have done complete manual transmission tear downs in addition I worked in a old style machine shop in m y youth manufacturing small batches of parts for one summer years ago. I have never worked with cnc equipment or the tooling required to cut gears but I have more than a cursory knowledge of precision assemblies and a working knowledge of some of the metallurgy involved. I would be interested to help get this project off the ground. Feel free to PM if you like . kind regards

 

[R-III-R Turbo]

All the drawings and details are posted up earlier in the thread, free to one & all

 

[SDR_11 Rocket]

All the drawings and details are posted up earlier in the thread, free to one & all

Thank you. I will search back through the thread. It is a little daunting given that there are 49 pages on this thread . It could be interesting to discuss technical details about this project sometime if you would have the time. I am on whatsapp and can share my contact details if it is appropriate. I am new to this forum and I do not want to overstep the protocol here but I am motivated by the old adage... two heads are better than one.
Ok I went through to page 16 and I see that your engineering skills are well beyond mine. That said I do feel that I would like to contribute in my own way if there is sufficient collective interest remaining to date is it merely funding that is needed to get this off the ground ? Additionally I do feel that if the right manufacturing facility was contacted for example a smaller outfit that is more flexible in their ability to introduce a smaller run of parts without the overhead. To this end I believe I could be of assistance in the networking. I do realize many here have already shook the tree on this years ago so if I am simply too late to the party and or the interest is just not there than that is a valid point. It just seems that it is worth having a go to see what could be done. To be clear I am a component rebuilder not a engineer but I am meticulous and would enjoy the opportunity to contribute to this community.
( I have not found the technical drawings but still searching )

 

[R-III-R Turbo]

Thank you. I will search back through the thread. It is a little daunting given that there are 49 pages on this thread . It could be interesting to discuss technical details about this project sometime if you would have the time. I am on whatsapp and can share my contact details if it is appropriate. I am new to this forum and I do not want to overstep the protocol here but I am motivated by the old adage... two heads are better than one.
Ok I went through to page 16 and I see that your engineering skills are well beyond mine. That said I do feel that I would like to contribute in my own way if there is sufficient collective interest remaining to date is it merely funding that is needed to get this off the ground ? Additionally I do feel that if the right manufacturing facility was contacted for example a smaller outfit that is more flexible in their ability to introduce a smaller run of parts without the overhead. To this end I believe I could be of assistance in the networking. I do realize many here have already shook the tree on this years ago so if I am simply too late to the party and or the interest is just not there than that is a valid point. It just seems that it is worth having a go to see what could be done. To be clear I am a component rebuilder not a engineer but I am meticulous and would enjoy the opportunity to contribute to this community.
( I have not found the technical drawings but still searching )

Top of page 46 has the post with all the details, pics and links to drawing files.
We did try Robinson Industries, a smaller firm with reasonable prices, and already very familiar with the Rocket III trans (Bill makes a billet version of the weak OEM 4th gear)... but no dice unfortunately.
In fact we didn't even get a reply!
Strange.

 

[SDR_11 Rocket]

Top of page 46 has the post with all the details, pics and links to drawing files.
We did try Robinson Industries, a smaller firm with reasonable prices, and already very familiar with the Rocket III trans (Bill makes a billet version of the weak OEM 4th gear)... but no dice unfortunately.
In fact we didn't even get a reply!
Strange.

Thank you. I will also contact Robinson Industries. I did find they still have the Billett 4th gear listed. Not to rehash everything but I saw a cursory reference in which you commented I believe regarding the option to modify the final drive ratio to suit this purpose in a simpler fashion. Is that just not workeable or is it not productive in terms of ratio gain ?
To be very clear if the reference file / image does not state "modify existing" then the entire component needs to be manufactured. ?
The machine shop said they would go over the CAD files and provide a quote at no cost. They asked what quantity for initial parts quality and testing I told them 1 each as far as I know ( please clarify ) but I was also thinking 2 in case it would be advisable to have parties on both continents test at the same time.