New Member West Midlands Area

[Calum]

TLDR; I need help identifying engine/build/parts. Skip to bottom if you're not interested in introduction

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Hello all!

Hopefully this is the right place to post an introduction

New member joining from West Midlands area and I'll be looking to some of you for help with regards to a hybridised RD250/350/400 project that I want to start undertaking.

At the moment I'm just in the process of collecting bits.

I run/own the Yamaha DT125R website forum and have had my Yamaha DT125RE for ~15 years.

2005 Yamaha DT125RE

This bike was stolen in 2010 from me and returned a day later utterly demolished  . It was rebuilt using an amalgamation of a myriad of parts, from Aprilia RS125 wheels, TZR 125RR Belgarda engine and Yamaha WR450F forks. Full details for the project has been documented on my forum and a video made to encapsulate the project in a succinct manner.

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My next project following this was an Aprilia RS 125. I built an Aprilia RS125 from scratch using a frame from Germany and whatever parts I could scrounge up from all over the web.

2007 Aprilia RS 125

For this I ended up using a clutch Master/Slave cylinder from a Ducati 916 (as shown above) and machined up an adaptor plate which sits inside the engine. 

Ducati Hydraulic Clutch Conversion Adaptor Plate

Ducati Hydraulic Clutch Conversion Adaptor Plate Fitted

The rest of the bike was bolted together with T5 titanium bolts, beautiful carbon fibre (courtesy of TYGA Performance' Catalogue) and a lovely well spec'd engine, utilising Gilardoni's Italkit 140cc revised cylinder, VHM head and the VHSB 34mm carburettor. The bike is practically brand new, handles superbly and goes really well. I reckon it'll do a smidgen over 100mph (indicated) with me tucked behind the visor and some tail wind

Again full details of this project can be found on my forum, with again a video summarising the overall project.

I have a good number of other bikes/projects on the go at the moment and I'm not here to talk to you about these bikes, instead the reason I'm here today is to scour up some knowledge on my next undertaking...

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In 2021 my brother decided to purchase a bike that he'd spoke of time and time again (RD350). I always considered him a bit of a pipe dreamer, but lo and behold when we drove up to Manchester to collect his new pride and joy (Hybrid RD350). I won't discuss/post this here as he likes to keep this bike under wraps (understandably). The resulting purchase made his current bike redundant and I agreed to take it off his hands for a nominal fee.

2004 Cagiva Raptor 125

This is a 2004 Cagiva Raptor 125 (many of you will probably now see where I'm going with this). It's not just any Cagiva Raptor 125, it's a Raptor in need of some love/care/attention/restoration. This photo was taken in the summer after a well overdue top end rebuild was done (piston had cracked along the crown and down the gudgeon pin area #TickingTimeBomb).

I haven't used this bike a great deal, if I'm honest, in 2021 it suffered an electrical fault leaving me stranded and as of a week ago the engine packed up...leaving me once again stranded. No fault of the Cagiva, I suspect the refreshed top end was too much for the bottom end, having stripped it down finding the top end is still in great condition from the recent rebuild. It hasn't been running right since late October and it was getting progressively worse. I actually only took it out to see if it could make it in an emergency... This is a bike owned predominantly by 17 year olds and has just not had the attention/maintenance it needs.

I bought a spare bottom end for this earlier this year with the intention of rebuilding it and having a drop in replacement and zero downtime for this fantastic bike, but seeing as the engine has given up the ghost the bike is now out of commission. This sent me back onto eBay scratching my head. I'm currently in the midst of another Rotax 122 engine build, for an Aprilia ETX 125 I acquired in 2022 that was desperate for a restoration, which I'll build slapping the Polini 154 kit to.

2001 Aprilia ETX 125

(I have only ridden this bike twice and then it was immediately stripped down)

So until I finish my Rotax 122 build the Cagiva is on hiatus.

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Where am I going with this?

I figured that my Raptor being complete and quite a rare little two stroke, that it would be criminal to butcher the frame for my new project. So instead I found a Cat C Frame Cagiva Planet (earlier version of the Raptor) on eBay (£65) and want to build another Cagiva Raptor but with a Yamaha RD350LC conversion. Since my brother bought his hybridised RD350LC I have absolutely fallen in love with the idea. Since then I've been toying with the idea of purchasing an early Yamaha RD350LC. I've seen a few that I've really liked/enquired about but nothing came to fruition. I've spoken to a few local gearheads that have pointed my in the direction of a hybridised RD350. USD forks, new rear swinging arm, modern wheels/brakes. All of this sounded great, however again I find myself in a situation where this would mean butchering a classic!

Secondly, once I'd added/changed the bits of the RD that I didn't like/want, that I basically would have been better off just building one with a tried/tested formula.

Here comes the Yamito RD350!

Cagiva Mito 125 with Yamaha RD350 Engine (Not mine)

So what have I got:

• Cagiva Planet 125 Frame
  
• Cagiva Planet Swinging Arm
  
• Cagiva Mito RD 350 Engine Mounts
• Yamaha RD250 4L1 Crankcases
  

I really don't know much about the RD engines and my plan was just to buy a complete RD350 engine that I could use as a donor. Since I am tied up in the midst of three/four other bike projects at the moment, all in a disarray of states, that I didn't want to drop $$$ for an engine just yet. I figured all I needed were the crankcases to get the frame and engine mounts welded together so that I have some form of commitment to the project.

I have spent the last few days scouring the web (this site looks like it'll be my home for this project) trying to learn as much as possible.

What I have come to realise (maybe someone here can shoot me down), is that I could probably build up these RD250 crankcases into a 350 or Athena 394???

I am looking for a bit of help as to what I am in for, what I've purchased engine wise, and whether it would be cost productive to just build these crankcases into a complete motor, other just source a complete engine.

My reasoning for this are:

• No matter what engine I get, it's going to want an overhaul
  
• Brand new aftermarket cranks can be bought for a smidgen more than a rebuild (PJME)
  
• I am not after concourse and thus not necessarily wanting genuine 350 barrels (Athena will suffice)
• Part compatibility seems to be a huge win across RD ranges (where I want your guys help)

I am a pretty slow rider (barely use the power out of my RS) and therefore I am not chasing BHP. The Cagiva Mito/Raptor engine is very capable, provided there is not a slight incline or head wind. As a result, I would benefit from a few extra torques and I believe the RD250/350/400/421 would enable that for me. I don't want to spend a fortune uprating the gearbox or any weak components and therefore finding the right balance between modernisation (Zeeltronic Ignition System/Carbs/Cylinders) and what the RD bottom end can handle will be important. I note that the conversion kit I've bought doesn't appear to support the Tie Rods for the engine. Some light reading leaves me to believe that the RD engines were revised due to twisting of the cases etc.

I will open up a thread once the formalities are done and, whilst my main website for project updates will be my own forum, I will maintain the build across both forums because your guys input is going to be invaluable.

That's my introduction, hopefully I'll be able to contribute more meaningful information in the future.

Calum

[4l04ever]

Welcome in :-)

[midlifecrisisrd]

Hi and welcome along

You seem to be no stranger to modding and hybrids so should manage fine

Just remember that if you are wanting an Athena or Cheetah motor you will need YPVS crankcases as they won't fit on the LC cases

If you are not chasing horses a 250LC top end would be a cheap option and make more power as standard than a balls out tuned 125 motor. Only issue would be that most modern exhaust makers will do their development on 350 LC or YPVS motors

A standard YPVS motor would be my choice

Steve

[Calum]

Hi,

Right, so I sort of want to abandon the 4L1 crankcases and source a YPVS 31K set?

My brother runs the 421 without YPVS and that thing is like a bat out of hell. Am I right in thinking that the 421 kit won't fit the cases I have bought?

Am I okay to use these cases merely to mock up the final transplant? I.e for my purposes the 4L0/4L1/31K will suffice me until the project is ready to accept the built motor.

I want to figure out if the stock wheels/suspension will suffice. Looking around the net it is a bit all over the place, saying that the rear suspension is okay, but the front end could do with beefening up. But that's all part of it and the chassis will be a lot easier to move around without the lump in it.

[dusty350]

Hi
Welcome to the forum
As said, if you want a big bore motor you will, currently, need a Ypvs bottom end, as the Banshee cases shares the same architecture as the Ypvs, so big bore barrels will fit, but not on an Lc. However, the mounting points are the same between Lc and Pv so a Pv engine bolts into an Lc frame with no modding.
There was a Ypvs bottom end at Kempton autojumble last week - complete except for the generator and rotor, and the fella wanted 400 quid for it - thats a good price for a bottom end nowadays - usually they are more expensive than that, and not unusual to see complete Pv engines for 2k or more.
I'm with Steve on why not go with a standard Pv but add a modern ignition, newer carbs and some decent pipes. That will give you a decent power upgrade and keep reliability, and not cost a fortune. You would add those parts to a big bore engine anyway to get the best from it, but save on the cost of the barrels and head set up. You can go to a 385cc without too much trouble if you really want to go bigger. Search the forum as there are lots of threads on big bore engines, and also speak to Muttsnuts on here as this is his "bread and butter"

Dusty

[Calum]

Okay fellas cheers.

I basically want something with the best aftermarket support. 350 will be plenty of power and for the moment, these 4L1 cases will serve their purpose to act as a template for the welding points. Then I shall relist them.

Yes that is a very good price. I will post here in the wanted section for a good bottom end then. Cheers. Likewise these 4L1 cases may be useful to someone wanting to do a 250 restoration, so I will be sure to advertise them here at a discounted rate. My plan was to get them vapor blasted by the chap who I plan on doing the welding just so my project has a clean slate.

I will put together some funds for a YPVS motor early next yeah.

[veg]

Welcome in, I won’t add anything to what Steve and Dusty have said, they’ve covered it all. Once you start, pop a build thread up and you’ll get loads of advice, assistance and encouragement. Whereabouts in the midlands? There are a few of us about and I’m sure anyone local will also be able to help out.

[JonW]

Welcome in.

Looks like youre done some great projects. Excited to see what you build.

[Calum]

Cheers veg. Gloucestershire area. Yes I'm sure I'll be seeking some expertise when the balls rolling. For the moment I'm just scouring parts.

I've got the engine mounts now, so will take the 4L1 crankcases I have to have the mounts welded in and it all vaporblasted. Once that's done I'll probably start saving for the 31K motor to go in it.

I'll get some photos up once the frame is welded and the cases are in.

From my research, it looks as though the front end would benefit from some stiffer suspension. At the moment I am thinking Ducati 916 forks (Showa? I haven't got Ohlins money...) and some possible machining to the yokes to make them fit. Since it's all Ducati (Cagiva was the parent company at one point) the rear wheel will be matching the front and it won't look so jarring. All that seems fairly reasonable coming to around £600 to "roll" the chassis. Apparently, the weight is mostly at the front, but a Suzuki RGV250 rear shock can be dialed in to help out at the rear too. But those posts are from 2010 and I doubt I'll be lucky to find anything in my price bracket.

But that's about it for now. Parts have been getting delivered like it's Christmas...but it's all manky stuff and needs proper cleaning before I post up any naught pics. All arranged with the fabricators in the new year, so expect to see something February time

[Calum]

Still doing this...just parts hording at the moment.

Basically have most of the Cagiva bits I need, frame has been dropped off with the 4L1 crankcases to weld in the engine mounts last weekend.

I'm looking/thinking, probably to buy a set of brand new Banshee 350 cases over used RD cases and build an Athena 421 setup using the Hot Rods crank. Still, five year project atm the moment, if not longer.