Wow, it's really sad how long this project takes to come to fruition...
Maybe I'm spreading myself too thin with way too many concurrent projects, maybe it's because for the first time in my life I've been doing stuff other than motorbikes/cars, but in any event December saw lots of time off for me and I was able to drag what I've been accumulating out of the wardrobe and start with some head scratching and engine work assembly.
Banshee/RD 350 Athena 421 Bottom End Assembly
With that all said, this month I took stock of my inventory and I came to realise that I had virtually all of what I needed to close the crankcases up on my Banshee 350 motor, in preparation of assembling the Athena 392 kit.
As some of you may know, there is free performance to be made if you port your crankcase's transfers to match the transfer ports on the cylinders. The Yamaha RD 350/Yamaha Banshee engines are notorious for leaving steps in between the transfers for the bottom end and the cylinders. Since I intend to run the Athena Big Bore Kit, this step is even more exacerbated.
In a nut shell, here I'll be marking out this discrepancy using some Dykem Blue engineering fluid, then scoring a visible outline using my Facom Scribe and then with my die grinder, porting the bottom end to match.
For reference again, the engine cases I bought were brand new direct from Yamaha. As such this gives a good example of how much, unmolested cases need to be grinded away.
[image: 01.jpg]
[image: 02.jpg]
You can get a rough idea of what needs to be cut by overlaying the gasket over the bottom end and marking out the material that needs cutting out.
[image: 03.jpg]
In my cases, I painted on the Dykem Blue and assembled the cylinder to the bottom end. This squished out excess fluid and left a visible line of where the cases meet the cylinder.
[image: 04.jpg]
Here I've placed a guitar pick into the location of what we need to cut. There is a visible step here that should be machined away using a die grinder.
[image: 05.jpg]
To ease the cutting process, I've washed away any excess Dykem Blue fluid and scribed a distinct line for where I want to cut up to.
[image: 06.jpg]
With all the appropriate markings made out, it's time to grab the die grinder and port the bottom end to match.
[image: 07.jpg]
[image: 08.jpg]
[image: 09.jpg]
I'm using a Rounded Tree Shape gold coated carbide burr. It's coarse flute geometry and titanium nitrate coating prevent the flutes from becoming clogged up and essentially cut through the alumiunium like butter.
[image: 10.jpg]
In only a matter of seconds I've roughly cut out the intended shape.
[image: 11.jpg]
Care MUST be taken here that you don't go too deep into the trenches. The crankcase walls are pretty thin towards the bottom and therefore care must be taken to avoid porting straight through the cases.
I've taken a photo here to give you a clear indication of how deep you'll want to aim to go.
[image: 12.jpg]
I've gone around and done a rough cut of the desired shape.
[image: 13.jpg]
I can quickly overlay the gasket to ensure I'm along the right track.
Note: The gasket used here is only a basic indication, there are cases where the gasket protrudes into the transfer ports and as such the gaskets need trimming. Therefore the method described above is preferred to get the perfect shape. This is especially true for ported cylinders.
[image: 14.jpg]
You can see here a Before/After photo and how now the pick is not being covered by the bottom end transfer ports and now correctly aligns to the cylinder transfers.
[image: 15.jpg]
The cases need to be thoroughly cleaned throughout to ensure no swarf is left anywhere.
[image: 16.jpg]
[image: 17.jpg]
These cases can be ported to quite some degree, since this is only running a mild big bore kit, the extent of the transfers needn't be too significant.
With this out the way, I can now start to assemble the bottom end with all the trick bits I've bought.
Bottom End Assembly
Now that the porting work has been completed and the gearbox rebuilt with a taller first gear, it's finally time to assembly the crankcase halves.
[image: 01.jpeg]
Here the selector drum can be installed along with the dog ears. The selector drum has been modified to aid easier shifting and easier neutral detection. It's a common mod for these engines and involves grinding away at the shift star to make the ramps more pronounced.
[image: 02.jpg]
The upper crankcase halves have been installed with lightweight titanium studs.
[image: 03.jpeg]
The 4mm Hot Rods crank can be installed, along with the straight cut primary gear. New seals throughout and I also acquired/installed new bearing clips that were allegedly tighter tolerances than the OEM ones. Although upon inspection they look much of the muchness to me.
The gearbox wouldn't be complete without all new bearings throughout, although my bearing was missing the much needed circlip. Luckily I have amassed enough spares in my workshop to salvage a bearing clip from another gearbox.
[image: 04.jpeg]
Here is the gear on the output shaft which was swapped for the 1st gear conversion.
[image: 05.jpg]
Along with the shift star mod, I've also got a modified detent arm (with roller bearing) and shift lever with the cut outs widened to give greater movement to the shifter mechanism.
[image: 07.jpg]
All the gears were tested/shifted to ensure correct alignment and engagement.
[image: 06.jpg]
The shifter mechanism operates on a cam which needs to be aligned prior to sealing. A relatively simple job once you understand what you're looking for, but easy to overlook. Once the alignment has been done, the locking nut can be tightened.
[image: 08.jpg]
Low profile grade 5 titanium bolts are used to affix the baffle plates and bearing retainer. Everything inside this engine is brand spanking new, since I have been building the engine from scratch.
[image: 09.jpg]
I've just ordered a Pro Design Billet Stator Plate, not that I'll need it as I plan on running a Zeeltronic ignition system, however it should finish off the bottom end nicely. I also ordered a chinese copy which looked perfectly serviceable.
I also decided to buy the Pro Design Wicked Cool Billet Head to fit onto my Athena Big Bore kit.
[image: 00.jpg]
[image: 10.jpg]
I still need to get a clutch basket and clutch plates, then my straight cut gears can all be installed and the bottom end completed. This will have to wait a few months as this is quite an expensive item to acquire.
[image: 11.jpg]
In order to get the top end assembled I need to ditch the Athena Pistons and order some appropriate ones for the stroker kit.
Carbon Fibre Moulding
On a side project, for the panelling on this machine I want a Carbon Fibre tank guard. This really isn't an necessity and I've merely been messing around with various techniques to try get a feel for how hard it would be.
Initially I started off with a moulding kit, but I ordered an inappropriate amount, failed to fully do the prep work and rushed the process. The result was the mould cracked upon separating.
Next I instead opted to just do a simple design to better understand the technique. Here I designed a part I wanted for the clutch cover in CAD then 3D printed the part to make a mould from.
[image: 15.png]
This too failed as I was unable to separate the mould from the part and as a result the whole thing was scrapped. I was starting to grow impatient and finally I decided I'd directly 3D print the mould and then make a carbon fibre part directly from the mould.
[image: 13.jpg]
To my surprise, this actually worked out really well (given the low-budgetness of it all), however I was not getting the desired effect. I wanted the lettering to be really pronounced as it is on the original part. However the lettering is feint and is mainly made of the epoxy which fell into the mould and not the carbon fibre.
I refined the approach, this time creating a mould-press to help form the lettering. I wanted to use a red carbon weave to accent the bikes final "Black" colouring.
[image: 17.jpeg]
But this again was unsatisfactory and I decided to ditch the lettering and call it a day for that idea and just focus on making a singular part.
[image: 12.jpg]
Although the weave got distorted, the part came out better than I expected.
[image: 14.jpg]
Sadly, I don't love the result, it actually looks better when the light isn't shining directly on it.
I am happy with how the part has come out, it's done as a budget part and it has worked to a degree.
Undeterred, I've given the moulding process another shot to see if I can fair up better. This time making sure I do plenty of prep work and don't rush it.
[image: 16.jpeg]
Actually pleased to say the moulding has worked! So I now have something that I could potentially make a carbon fibre part from. I know you can get reasonable jobs from this type of setup, I am not looking for perfection here, just something to give the bike a bit of bling would be nice.
Sadly, I ran out of carbon fibre weave to actually progress with this and I'm not sold I want the red carbon/polyester weave, however I've seen you can get red pigments for the epoxy resin which I may give a go with this mould.
Conclusion
Still a LONG way to go, but having the crankcase halves assembled is a huge milestone for this project. I'm hoping that next year I can get the cylinder work completed and the engine closed up. Once this has been done, I'd like a Bitubo steering damper welded to the frame and then the frame and ancillaries can go off for painting. Then it'll be case of rolling the chassis!
