Creating my own motorcycle scratch

[Old England]

With engine mounts welded to the frame and some suitable period style racing handlebars bent up I could now heave my creation into the daylight. The rear hub is from a Honda 250cc road bike much modified to suit my needs. Very satisfying to get to this point but there was much complication ahead....

[Patio]

I am impressed.
Most people would build a motor, or a frame, or a girder front end, with triple trees, but not everything.
Patio

[Old England]

A couple of reasons Pat: First I had been let down so many times by suppliers with my racing bike projects. The final straw was waiting months for a crankshaft to be rebuilt for my blown methanol burner only to find they had forgotten to weld the throws of the built up crank as instructed. Second, once I started I couldn't stop, and it is very satisfying

[Old England]

OK I need to explain the transmission now as it is a little complicated: The DR750 engine I used for the crankshaft is gear primary drive on the right and final drive from the gearbox is on the left. I had decided to use the Suzuki gearbox internals but British bikes of the period I was concerned with had chain primary drive on the left, usually with final drive on the left too. So to get chain primary drive on the left I flipped the gearbox internals 180°on the axis of the shafts and by running my engine backwards the bike would go forwards. Fortunately the gearbox dogs were not undercut so it worked fine, though scheming this out was the easy bit! My final drive would be on the right (a cross over gearbox) but this was not unknown in the 1920's.
In my arrangement the crankshaft primary gear became the timing gear driving my half time camshaft gear, and the taper on the other side of the crank that held the alternator rotor now had a small sprocket for the primary chain. I realised that if I cut the large primary gear off the clutch basket I could then replace it with a large primary sprocket. A slight problem was the clutch lifting mechanism as on the Suzuki this is in the primary cover and does lift the clutch. No problem just drill a hole through the centre of the gearbox mainshaft for a conventional pushrod from the other side.....
Now the thinking was over it was time to design a gearbox housing and replicate the complex die cast interior of the Suzuki crankcases, this proved somewhat difficult!
I've attached a couple of rough sketches which hopefully will explain the above rambling.

[Old England]

Here are some selected photos from year 3: stages in making the gearbox casing, lots more swarf!

[Old England]

Hopefully folks are still interested so I'll press on:
First photo shows the large primary gear separated from the Suzuki clutch basket and in the centre a new sprocket modified to accept the clutch shock absorber springs.
Photo 2 is a trip back to the nearly complete cylinder head, you can see the rockers are now ready to be welded onto the shafts as I mentioned earlier. Lots of the parts here are dull nickel plated for period correct appearance and all bolt heads on the bike are machined flat to remove forged in specifications. This really makes a difference to the overall appearance of the bike, along with flat screwdriver heads on case screws etc., no allen bolts!
Photo 3 is the cam billet of nickel/chromium/molybdenum tool steel. I was so excited to make this I forgot to photograph the process. Suffice to say the lobes are formed by cutting lots of flats using dividing head on the mill, these are then filed to a nice smooth profile and polished before heat treatment. See the next photo for the result, the gear on the left has a groove in its shaft to drive the oil pump.
Finally it's beginning to look like a motorcycle at last though there was still much to do. The petrol tank is in two separate halves: the right for fuel and the left contains most of the total loss ignition system and a small battery to provide the volts thereof. Sheet metal work is not really my thing and the tanks were a nightmare to make. The left tank half can be very quickly removed with all the electrical gubbins and battery inside.
The exhaust was bent using my old hand tube bender and was the only part I couldn't nickel plate myself for quite obvious reasons!
I'll wind this story up with the next instalment.

[JackF]

When finished you must provide us with a video of you and your bike in motion.

[Old England]

When finished you must provide us with a video of you and your bike in motion.

Will do Jack

[NP317]

Remarkable vision, planning, machining, and success!
Thanks for sharing.
RussN

[Old England]

Remarkable vision, planning, machining, and success!
Thanks for sharing.
RussN

Thank you Russ, of course some mistakes were made but fortunately I managed to transform them into 'features'
Carl.

[Old England]

In the Summer of 2016 the bike made it's public debut at the annual Brooklands Museum Motorcycle Show, creating lots of interest and a few confused motorcycle enthusiasts who tried to identify what it was. The fact that a number of them thought it was a genuine Brooklands racer was very satisfying. Unfortunately there were a few minor things to finish so I wasn't able to start the bike and do some demo runs. However I did get to pose on the crumbling remains of the famous banking underneath the replica 'Member Bridge'.
Only two weeks later I was finally able to spin up the rear wheel on my home made (of course ) starting rollers and dump the clutch, to my amazement and relief it burst into life almost immediately. Later in October I entered my first sprint race meeting where it became obvious that the period hand change was a major handicap to say the least: On the first run I zapped a Yamaha R1 1000cc four off the line despite massive wheelspin and going sideways, but by the time I'd straightened up and changed into 2nd gear I was nearly at walking pace
Towards the end of this video there is action footage from that first race including our Daughter and I fumbling with the hand change trying to find neutral after starting for the first time, then a later run where I repeated the quick/slow race style against a Honda 1000cc V-twin followed by very slow when a pushrod jumped out
Despite the hand change problems the bike managed to hit over 80mph in the 1/4 mile so I was pretty pleased and apart from the pushrod nothing else fell off or broke, always a good sign!
[youtube][/youtube]

[Old England]

During the winter of 2016/17 I made a foot change on the correct period right side. As a rider of Japanese and Italian bikes for my whole life ie left foot gear change this meant I had to really THINK before acting when riding the bike. The lovingly turned teak and brass knob I made for the hand change was transferred to our Daughter's car when the original gear lever knob fell off
2017 saw a return to the Brooklands Museum motorcycle show and a first run up the famous 'Test Hill'. Created in 1907 the hill was pecifically to test the hill climbing ability of very early cars and motorcycles, short but rapidly increasing in gradient to about 33% near the top. This video is of my very first tentative run up the hill and begins with me trying to remember which side the gearchange is on
The track turns sharp right just at the top of the hill so it's a good idea to slow down before cresting the rise as there is not much run off; a number of well known vintage sprint racers have gone straight on in the heat of the moment and crashed; including my lovely wife who took off on her race bike and crash landed in the mess of potholes and gravel!