The Aphrodite Project (Cagiva Planet 125 RD 350 YPVS 421 Conversion)
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Introduction
It probably comes to no surprise of anyone that I've decided to build myself one of these beauts. With my recent posts showing off my brothers Cagiva Mito RD 350 converted bike.
That after one spin around on the block on one I just had to have one!
To those of the uninitiated, the Cagiva Mito has been famed in recent times by being a really common conversion for Yamaha's RD 350 engine. It has gotten to the point where by you can simply buy the conversion kits online for a DIY enthusiast.
This project actually dates WAY WAY back in time to around 2015 era where my brother would incessantly go on about them to the point where he eventually ventured down the path with buying a Cagiva Raptor 125 to perform the conversion to.
Now my Cagiva Raptor which he sold to me the moment he bought his already converted Mito 350.
I 100% absolutely agree that the Mito 350 is simply the better bike to have and perform this mod to, but I simply don't ride my RS for the fact that it can be very uncomfortable to ride after 20 or so minutes. I must have damaged my wrists as a child as I even struggled with this fact on my RS 50 when I was 16 all those years ago.
The Raptor, or Planet that I have bought, is a streetfighteresque motorbike that simply has more relaxed geometry and for longer blasts is simply and utterly bliss to ride. I almost just bought an RD350 factory phresh, but I wasn't a fan of the OEM setup and just felt it would be criminal butchering a classic bike to tack it up the way I do.
So instead, November 2023, I flogged to eBay in search of the donor chassis for this project and landed with a Category C Written off Cagiva Planet 125 for a measily £65! Bargain.
This will be a labour of love and like Peanut Butter and Jelly or Bacon Lettuce Tomato sandwiches, this project matches together two of the best things to come out of the two stroke era of motorcycles; the famed Yamaha RD 350 motor and the Italian 125 sports bikes that have made the likes of Rossi what they are today, so sit back, relax and grab a brew as this is going to be a long one.
Initial Prospect
I will be using a 2001 Cagiva Planet, along with the the Yordy Reyna kit, to align the engine into the chassis whilst maintaining the rear wheel alignment. This modification will work with all Mito Evolution 2's and Cagiva Raptors. The Planet can be converted to a Mito if I so wish, however I am pretty set on just sticking with the Planet/Raptor setup for the moment, however this is subject to change as the Mito is definitely a sexy machine.
In November 2023 I dropped a few hundred quid on:
- 2001 Cagiva Planet Frame
- Cagiva Mito Swinging Arm
- 1982 Yamaha RD 350 LC 4L1 crank cases.
- The Yordi Reyna engine mount conversion kit
It is here that I made my first critical mistake.
YOU DON'T WANT THE 4L1/4L0 crankcases.
Yes the engine will fit into the all models of RDs and the conversion kit is correct for it, but the crucial part here is the stud pattern on the crankcases are different, along with the internal spacing of both the crank and gearbox. They only did the LC for years 1980-1982 before they moved on to the far superior LC2 YPVS models.
These cases were sourced at no small expense, but I may actually reuse them and drop them into my DTR some point in the very distant future.
This is annoying, but is no dramas, I'm learning as I go and I was able to whisk this all off to the fabricators for the frame to be modified and the engine mounts welded in!
The engineer was very busy, so these were dropped and left with him for a quiet period where he could undertake the necessary modifications. Meanwhile I turned my attention to acquiring the parts I need as well as sourcing another engine that I will want to use.
The market for Raptor/Planet bits is rather volatile. Where possible you merely want to search for "Mito" parts or comparable Aprilia RS 125 parts. These triple clamps cost a considerable amount of money, and the a week later a set came up for pennies
Like the Aprilia parts, the metal here is of a good quality and a few minutes with the old polishing mop you can quite easily achieve a nice finish.
I hear the Suzuki RGV 250 is a good choice for rear suspension so I managed to snag one that is in dire need of a rebuild. I have stripped it down and stored it ready for it to be rebuilt.
Similar story here with the clocks that I had with the clamps...
Bought one set of clocks at an exuberant cost, then a week later another one popped up for pennies.
I bought both as I suspected I may need to butcher one up pretty badly for this project as I have some plans which I will discuss later.
I am by no means sold on these...
But my main motivation here is that 3 spokes < 5 spokes so must be easier to clean! Also for similar reasons above...I have another reason why I've decided to go 3 spoke on this project.
Since I made a bit of a faux par on the engine, I've been hitting up the rdlccrazy forum to ask for assistance. I was pointed in the direction of a very helpful blog about how to build my engine.
I am more than happy to run Yamaha's RD 350 YPVS, if I am honest with you I barely take my 125s to the limit of their power let alone a 350cc. The fact is, I simply cannot be bothered with the headache of the YPVS system, although it is very reliable, I just like the simplicity of running open ports.
The plan here then is to run the Athena 392cc Big Bore conversion kit with does away with the powervalves. These are very popular and a common modification to this setup is to use a stroked crankshaft to take it out to 421ccs. The problem is, as I alluded to earlier, there really isn't much support in the aftermarket scene for the early LC engines and if you want to do this, then you really want the LC2 YPVS engines....or better still the Banshee 350 engine.
The Power Plant
The plan here is to run an RD 350 bottom end, stroked and bored to 421cc. I was unsure about how this was achieved, but JonW over at RDLCCrazyForum was able to talk me through the process. He basically ran the scene for these motors back in the UKs hayday, but his website has long gone and he recommended using the wayback machine to visit his site to figure out how this done. This to me was a bit faffy, instead I have rehosted (with Jon's permission), the portion of his website that deals with the big bore conversions on these engines.
RZ350 RD350 Big Bore Primer
^^^^This is a MUST read for those looking to get the most out their big bore kit^^^Once I read this, I understand what steps I needed to do.
- Banshee 350 Crankcases
- Athena 392 Big Bore Kit
- Hot Rods +4mm Crankshaft
Results in 421cc of two stroke Godness!
America and the Banshee 350
Just off on a tangent here but to give the uninitiated a quick background on what I'm talking about here.
The Banshee 350 was Yamaha's answer to Suzuki's LT500R, or the Quadzilla.
In a bygone era where manufacturers dared each other to try and out do one another by making more and more ridiculous powerhouses, back when, at the time, the US Government put a ban on further development to the ATV market.
The US didn't get the RD 350, instead they got the RZ model, which for all intents and purposes is the RD. Unfortunately this was sold in limited numbers, due partly to California's strict emission regulations.
What the US did get in large quantities was Yamaha's Banshee 350 and it is actually this little beastie which I have managed to source brand new in box direct from America...
I couldn't understand the US's fascination with the Banshee 350. I must have heard about this vehicle a thousand times before, but never paid it any attention. I think they looked pig ugly and am generally not a fan of quads to begin with.
For those who think the same, then you need to watch this video!
https://www.youtube.com/watch?v=yZruUQVTqmI
Watching that video just gave me a whole new level of appreciation for what Yamaha did. The fact is, they made these quads from around 1986 all the way up until 2012. They wanted a piece of the ATV market, but didn't want to outlay the cost of developing a new motor to put in one. Instead they recycled the RD 350, which was selling extremely well in Japan/Europe, and built the ATV around the RD 350 engine. They felt that the 60Hp the RD was putting out was rather silly for the ATV and detuned them to around the 40Hp mark. They also "undid" some of the work they made to the RD series of engines, where allegedly they left room to bore the bottom end out to accept larger cylinders, much like they were doing with the DT's at the time, but this never came to fruition. This makes the Banshee 350 bottom ends stronger as they filled in the void gap left in the crankcases. This is a common mod to strengthen 350 cases up, however buying the Banshee variant saves this process. Other than that they are virtually identical, except for the omission of the tachometer (which I am not planning on running anyway).
These ATVs were sold in a variety of markets, but it's the American market where they really sold well. And it's because of this fact that the scene in America is utterly HUGE! If you're a two stroke lover, like me, and you want the ultimate two stroke experience, then getting into the Yamaha RD/Banshee scene is about as close as you're going to get to having the ultimate 500 V4 experience. Just as a side note, they are so big in America that there are companies out there that make billet crank cases for the Banshee 350!
Taking the overall displacement out to something like 1200cc when you include big bore/stroker kits!
Utterly Ballistic!
The tuning scene for these legendary motors is alive and kicking in the United States of America and that's exactly where I sourced my crankcase from, along with a few other very tasty treats.
Back to Aphrodite Project
Brand new in box direct from America from a company called Cascade Innovations, delivered in a matter of days, is my Yamaha Banshee 350 crankcase and what I will be using to build my power house with.
I mean how cool is that!
Absolutely factory PHRESH, with a capital P!
I was so excited to receive these as this is a major stepping stone to be building my dream motorcycle. So thanks again to Cascade Innovations for sending this over.
Because I am an idiot, I decided early on, after discussing this over the RDLC Crazy Forums, that I was merely going to be building a brand new RD350 engine.
So it's many trips to Fowlers later getting all the odds and sods for the internals.
Farm and Sand Toys (F.A.S.T.) have you in mind if you want some trick bits...
This is their modified selector drum star, shifter gear and detent arm. Alongside the extended water pump cover and their billet neutral switch.
Next was heading off to Mad Bike Designers to order the critical part of the build, the stroked crankshaft.
I have various other bits, but no photos as of yet, these will come in time however.
Chassis Development
With the power plant understood and on its way to be delivered, I turned my attention back to the chassis portion of the project. I contacted the engineer who was taking responsibility for the engine mounts and spent the day with him making a start with the fabrication of the engine mounts.
The Reyna kit comes with instructions, but they weren't the clearest in the world.
Before I begin, I want to give a shout out to Matt@MB Engineering and Vapour Blasting for doing this side of the work. Unfortunately this is beyond my skill set and I do rely on others from time to time. A real professional and was more than happy to undertake this work at an EXTREMELY reasonable price. When Matt isn't doing up rally cars he's happy to undertake other projects. So thanks again Matt it was really appreciated.
By this point in the project, I realised I had dropped off the swinging arm without the spacers and felt it would be useful to bring a shock and suspension knuckle. I assembled it all on his bench and we compared/contrasted what we had with the vague instructions until we had a plan of action.
The first step was to cut off the original OEM mounting lugs at the front of the bike and move them above inside the trestle.
Once we'd done this, we could turn our attention to drilling the appropriate hole for the swinging arm to go through and then mocking up the rear engine mounts.
We managed to get the swinging arm on and offer up the mounts to the frame ready for a quick tack weld.
Lots of
effingandjeffingfrom Matt as 23 years of oil came pouring out the frame as it sweated, making it incredibly difficult for him to TIG weld up.This is not to be underestimated! I got there at 10:30 and I didn't leave till 17:00 and all we'd achieved were the preliminary tack welds.
Unfortunately, the engine fouled the rear mount and we needed to make various modifications to the kit to get it all in there.
I left the day feeling pretty happy with what we'd had achieved. Again this was a huge milestone in the project and by the time I had left I had an RD 350 fitted into the chassis of my Planet. Matt had only tack welded the parts in place and I left him to it for another days work of cutting and welding and general tidying up of the parts.
The parts have been nicely sculpted and welded in.
Although I will be having these parts powdercoated, this is a five year project and whilst I'll be assembling and disassembling the bike many times over, it's nice to have it all cleaned.
Luckily, Matt has just the thing with a great big whopping vapor blasting cabinet.
I asked him just to give it a quick rinse as it's all getting painted anyway.
Whilst Matt was busy modifying the frame, I turned my attention to the front suspension.
For clarity, I have ridden my brothers Cagiva and I think it's absolutely fine. It handles fine and it stops fine. There are others on the WWW that disagree however. Others seem to think that the extra weight from the RD motor causes the front suspension to sag.
From my perspective, swapping out the front with something with extra stopping power to match the increased power would do wonders for my project.
With this in mind, I purchased a beefed up front end from a 2008 Kawasaki ZX10R to fit to my project, this comes back to what I was referring to a long while ago with regards to clocks.
To itemise this for others I plan on running:
- 2008 Kawasaki ZX10R Front Forks (Generation 3)
- 2008 Kawasaki ZX10R Front Brakes (Generation 3)
- ~2000 Era Ductai 916 Front 3 Spoke Wheel
- Cagiva Raptor 125 Triple Clamps
Verdict....
It's tight...
Very Tight...
Like I may want to shave the back of the calipers tight...
That said...it might work.
But there are issues...
2008 Kawasaki ZX10R Front End on Mito/Planet/Raptor Triple Clamps
As mentioned earlier, the plan is to run a 2008 era, generation 3, Kawasaki ZX10R front forks/brakes in the original OEM triple clamps.
The first problem I see is that the ZX10R triple clamps have a wider offset than the Mito setup. This means that the spindle protrudes the fork leg and that it is not possible to tighten up the front spindle.
Secondly, there is simply not enough room to run the speedo drive.
Finally, as mentioned, the brake calipers very nearly foul the wheel (yet to confirm without spacers).
My plan here is to offset the spindle 15mm towards the edges which should allow me to tighten up the front wheel. However the spindle and the nut occupy the region on the fork leg which the legs clamp to, so I will need shims to back fill this to. I will then need a speedo delete spacer made up along side a normal spacer.
I knocked this out in CAD and 3D printed some test pieces to trial fit.
Not sure how much people are interested, but the Mito 350 is quite a common conversion and I didn't see much information on the web specifically about what people have done.
So the problem I have with using the ZX10R forks inside the Mito triple clamps is that the clamps are narrower than the ZX10R forks. As alluded to in my original picture, the spindle protrudes the fork leg and therefore it is not possible to torque up the front wheel. Furthermore, the spindle sits on bushes inside the fork legs. This was probably done for some good reason so it's probably best not to mess about with that too much.
I've spent the day making notes and drawings and I've come up with two options:
- Use ZX10R triple clamps and swap the bearings and inner headstock spacer out + bearing cup if needed
- This was similar to how I did this type of conversion on my Yamaha DT125RE
- Space out the spindle equally and backfill the bushes on the inside and appropriate spacers
- Possibly may need to machine down the wheel nut bush
For simplicity, I'm going to send these CAD drawings off to a machine shop and get the appropriate spacers made and see how it all fits, but I'll attached a render to help explain.
The render shows three different states alongside a screenshot of spacers necessary. Looks like my Ducati wheel accepts a speedo drive the Mito yokes are simply too narrow to use one so on spacer will delete the speedo drive altogther.
Going to the colour render the colour denotes the following:
- Pink
- The Wheel Hub
- Silver
- The Fork Leg
- Red
- Wheel Spindle
*Blue - Spindle Outer Shim
- Wheel Spindle
- Yellow
- Spindle Inner Bush Shim
- Green
- Wheel Spacers
The idea here is to make up the original triple clamp length at the spindle, by moving the spindle equally outwards on both sides so that it no longer egregiously protrudes the fork leg.
In the colour render, the top image highlights the problem. The spindle far exceeds the fork leg and bottoms out on the spindle bush/nut. It is not possible to torque up the nut and there is now play in the forks.
The second image demonstrates where each of the proposed parts would fit. The Blue spacers will shim either side of the spindle and will allow the spindle to sit further in the fork leg hopefully not bottoming out the inner bush nut. The bush/nut may need to be machined if it still bottoms out and a new Yellow Spindle inner shim made to take up the slack.
The Green spacers can then be slid into position, although the speedo drive unit side my have to be inserted into the wheel first prior to offering the wheel. I've made it a snug fit so it should stay in when offering. The second shim is only a few mm so may prove difficult.
The final image shows how it should all be mounted in situ. The spindle still protrudes the fork leg, but it's now equal on both sides. Hopefully it allows for the nut to be torqued up without compressing the lower fork stanchions and/or leaving them loose.
This may prove not to be successful, but I'll cross that bridge when I get to it. A shorter spindle would also go a long way and may be a far more simpler solution, but I'm just working with what I have.
I have sent the CAD designs off to be CNC machined. In the meantime I need to look at the speedo drive replacement.
Speedo Drive Enclosure
I want the bike to look close to factory, which means retaining the original OEM clocks. The problem here is that it is simply not possible to drive the clocks without the speedo drive in a feasible manner. As I've alluded to from the opening paragraphs, I sort of anticipated this from the get-go. I always suspected I'd run a custom fork setup and will be at onus of what I ends up using to determine how I will run a speedometer.
So back to CAD I decided to model the original speedo enclosure to enable me to make reasonable modifications to still have a working speedo.
With the speedo meter dismantled I spent the day modelling it in CAD.
And in no time at all the models were sent off to be printed for me to examine.
And it's pretty darn close!
I was well happy with that result, and for a measily £20 delivered to my door! Bargain.
With that element de-risked, I set about dismantling one of the clocks that I bought. I chose the one that looked the most beaten, as unfortunately I had to dremel it to get it open.
I removed all the gearbox internals of the speedo drive and I now have a speedo meter which has a direct drive capability added to it. What this means is that turning the back of the clocks is directly coupled to spinning the needle.
Now that I have the designs for an OEM enclosure in CAD, the plan is to modify this enclosure so that it can house a stepper motor which I will mount to the back. I will then use a hall effect sensor at the wheel to calculate wheel speed and step the motor accordingly.
These clocks also have no provisions for temperature sensor, so I may also include some sort of temperature display readout underneath the indicator lights. I still have to design and thing about this some yet.
Conclusion
That's your lot I'm afraid. There is some odds and sods that I have left out of this blog post. Of course, I don't actually expect anyone to read any of this nonsense. This is merely a way for me to document my findings and a therapeutic/cathartic way to relieve the stress of throwing time/money/life.
That said, there is some useful information here that may be of value to someone in the future looking to embark on a similar conversion. This, if nothing else, is just more information about the process and hopefully allows someone to not make the same mistakes that I did.
Until the next post...
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@Calum This is a well impressive project, I read the entire post (hope I've fully understood) and let me make clear straight away I've never taken on something of this magnitude.
Firstly I think your use of a Raptor as a base could open some new doors within the Yamito community. How different is the frame to the Mito? Because potentially at this stage you could engineer a quick change, plug-and-play system between naked for street use and fully faired for more serious track day/fast road riding, a bit like people who have a Supermoto wheelset for their Enduro bike so they can get out on tarmac as and when the mood suits them. Has anyone ever done this with a Yamito? It would be quite special to have this facility as it could be a modern RD350N/R1-Z250 one week and a sports bike the next.
Pretty cool write-up about the ATV scene in the US; every time I see an LT500 I wonder why Suzuki never made a liquid-cooled, power-valved RM500. I guess the US MX market was moving further towards 250s at the time due to the popularity of Supercross.
I do understand your preference for 3-spoke wheels but in this instance I think this is causing a few headaches. I wouldn't be happy with the calipers being that close to the spokes either, plus I'd have reservations about machining material off the insides of the caliper bodies. Do you have the ZX-10R front wheel, was it included with the front end you bought? And is there a reason you don't want to use it? Is this the correct ZX-10R (I'm not really up to date with modern sportsbikes so I had to look it up)?
https://www.motorcyclenews.com/bike-reviews/kawasaki/zx-10r/2008/
If yes, I'd say that is a nice looking front end as is, and the 5-spoke wheel would blend reasonably well with the stock 6-spoke Mito/Raptor rear meaning you could just go with your Option 1 and use the ZX-10R triple clamps. It would surely be easier to make a complete front end fit than start experimenting with inner/outer shims and custom wheel spacers. As stated I don't know too much about these but there's one for sale on eBay ATM running the stock Mito rear suspension besides a custom Maxton shock (I think you'll definitely need one of these), ZX-10R forks and Ducati front wheel with what looks like some outer wheel spindle shims like the ones you've proposed in order to run Mito/Raptor yokes; is there a definite red flag about the ZX-10R front wheel amongst the Yamito community?
If you're determined to run 3-spokes, have you considered something like an RGV250 VJ22 or GSX-R400 GK76A front end? Those Kayabe USDs were quite well-known back in the day for superb ride quality and adjustability, and a lot of RGVs found their way onto the track meaning there's a lot of setup info out there.
And regarding the speedo question, I think if I was taking on fitting a different engine into a chassis with all the myriad of engineering problems that entails, certainly in the short term I'd be more than happy to bungee/JB Weld a cycle computer to the top yoke just to get the bike MOT'd and do some initial testing.
I suppose my underlying thoughts with anything like this are keep it as simple as possible, and don't have too many headaches at once. When I was RC car racing one of the guys at my local club was very keen on Tamiya which to those unfamiliar, are basically the Honda of RC in Japan. However the UK Tamiya importer is quite petty-minded meaning the kits and spares are ludicrously expensive, and they pull other tricks like waiting 6 weeks before doing a Japan spares order so they can save shipping costs by getting it all freighted in one 40' container; not ideal if you're racing next Sunday. Anyway undeterred and against everyone's advice (including one person who very kindly lent him a car/setup to tide him over whilst he was saving up for his own), this guy bought the Tamiya 1/8th buggy which cost him twice as much as the more common cars we were all running, he didn't have a single spare part and so was scared to even try and lap fast for fear of breaking something, and his entire racing season was an expensive disaster. To add insult to injury he was really into F1 and his expensive Ayrton Senna tribute graphics kit wasn't resistant to nitro fuel and it visibly upset him when they got ruined the 1st time he refuelled during a 15-minute final. In the end he gave up racing which was a shame because he was quite analytical, he was getting faster week after week with the loan car and was generally a joy to have along.
Like I say a Yamito build is not something I've ever taken on, fitting a a 350/421cc twin into a 125cc chassis is impressive enough in itself so my instinct would be to tackle every other aspect of the project in the simplest way possible for now as there will be plenty of time for further improvements down the line.
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@HOTSHOT-III No you're pretty spot on to be fair.
The Mito/Raptor is the same, like the Aprilia RS and Tuono. So you can easily bolt fairings on and off, the only difference is the rear subframe and the headlight surround. But it's an afternoons work of you have the bits.
I think you're right though, I may go Mito in the end but for now the naked setup is what I have chosen. This isn't the first Raptor 350 build, a few others have done it.
People are now doing the swaps into the MT125 chassis to keep it all in the same family.
Yeah as I say, it's a five year project so I am not in any hurry.
I definitely think the speedo setup will be the last thing that gets dialed in and tackled, as you say, the idea is to keep it simple. It's not a MOT requirement for the speedo to actually work, it just needs to be fitted, I can use my GPS on my phone for speed in the short term.
Yeah that's definitely an interesting story about the RC car. I was looking at getting a Honda NSR250 but it would be the same story, parts ridiculously rare and I'd just be worried about breaking it.
I'd be skimming the back of the calipers and only by a few mill to make the clearances. Regardless of what solution I go with, I'd still need to align the front wheel with the back, the Raptor yokes are being used as they have provisioning for the flat bars, the ZX does not.
I could design something in CAD to use the ZX bottom clamps and new top clamps that can accept the flat bars. It's certainly all yo play for.
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Propa OG that m8 looks mint awesome design can't wait to see her all running
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@yeolderaver Cheers bro, yeah it's slowing down at the moment as someone crashed into my car on my drive and didn't bother to leave a note, (it's a private drive 30+ metres off the road!) so I got that to repair this month
I wouldn't mind, but I don't even drive the car, it just sits on my drive. I've done 1000 miles in it in the 5 years I've had it.
Anyway, it was cheaper to buy these as an item of 5 as they have to set up the CNC machine, so figured I may as well get a few extras and float them on the forums see if anyone is interested...
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Aww thats savage hope you get some good luck from it all somehow. And yeh keep hold of them collectors piece indeed are there many of these conversions about? as first I heard here from you did show one my friends and he says looks epic hes been building chops n rats for many years and says thats going to be a top ride once completed so thanks for sharing your journey with us all bro wish I had funds for another project mot failed on DT wiring and brakes its not been right since some lil menace stole it so lucky I got it back but she aint the same now.
Must be a reason for our woes must make us better in the long run or something hope some cash comes your way soon so you can get this girl on the tarmac
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@Calum Sorry to hear about your car bud. +1 for I'd keep hold of those extra clutch cover inserts if I were you, they look ace and are a part that can get rubbed/scratched just from riding so it would be cool to be able to just bung on a fresh one as and when.
