New 700cc Outfit


XS650 Guru
Top Contributor
Reaction score
New Zealand
Watsons RD 700.jpg
700 cc Classic Outfit

The basic idea for this arose during a long drive back from a race meeting. At the meeting we realised that to go any faster we needed more power than we could safely get from our XS.

The class we compete in at most meetings has limitations on engines year of manufacture, wheel size, brakes and suspension. Basically the engine must be in production before 1973. Unless used on the production bike flat slide carbs, monoshock, floating discs and brake callipers with more than two pistons are prohibited.

The easy way would be to go the BMW route as Norton’s and Triumphs require too much money to get going fast and tend towards being fragile. However we are Yamaha fans.

Combining two Yamaha 350 motors together in a sidecar was done pretty early on in Australia. I read in an Issue of Old Bike Australia about the man Alex Campbell who did it. It also said that engineers from Japan travelled to Aussie to view the machine all this was before the TZ 700 was released. For those of you who want to read the article it is in Old Bike Australaisia issue number 62.

An RD 700 outfit was also built and raced in New Zealand (I think in the 1970’s) by Garry and Clive Watson.
The photo at the top is the Watson 700.

From looking at the Watson motor it looks like the two crankshafts were used being joined between the second and third cylinders. It also appears to retain the RD transmission which I think is an advance on the Australian version which used a Norton gearbox.

In England by 1972 Ted Broad had grafted another cylinder to a TR3 to build a 525cc solo.

I really admire what these early guys working in isolation without factory backing achieved. It must have been so much more difficult than now.

Currently in the UK Alan Millard (who seems to be able to reconfigure any motor layout) and a few others are adding extra cylinders to Yamaha two strokes. There is also a 4 cylinder LC 700 being built as I write.

In the US if you have the money you can buy a beautiful set of billet 2, 3 or 4 cylinder cases for banshee cylinders.

So as you can see idea is not new, this is how we are attempting it. Whether we are successful or not remains to be seen.

I must also say that most of the info on engine modification has been gleaned from the Two Stroke World Forum. Like this forum it has some very knowlegable members who generously share their knowledge.

This thread will have some images that have been posted before in other threads but future updates to the RD 700 outfit will only be posted here.

The outfit will be a new build not a repower meaning new frame, running gear, motor and body work.
Brakes, we will be using XS discs and callipers. The discs have been drilled and bead blasted one was refinished by grinding. The callipers were bead blasted and new aluminium pistons made, new seals, bleeder valves and pads bought. All wheels will be braked.

Wheels and hubs we are using 10 inch diameter mini mag wheels, custom made hubs and axels.

Front end will be a leading link type with dual YSS shocks and rear suspension will be conventional swing arm again with dual YSS shocks. The platform will be front and rear exit on the left side.


Two RD 350 engines with modified cases and common crank using 3 labrynth seals.

Clutch will be upgraded using a Hinson banshee basket with straight cut gears, FZ 600 plates, standard steels and upgraded springs and hydraulic actuation.

The standard RD has helical gears and the extra power may load the crank axially excessively. Interestingly the first TZ 700’s used a XS 650 clutch and we considered using one but there was a bit of work required to get it to work and the banshee clutch is almost a direct swap, has a cush drive and straight cut gears. Multiple problems solved with one expensive item.

Oil pump has been removed and blanked as has the tacho drive. We will be using premix and an electronic tacho.

Transmission will be stock contained in the right hand case. The output shaft will be extended and supported by an outrigger bearing. A simple means to mount and change the front sprocket needs to be devised.

Starting will use the kick shaft modified to allow remote start by electric drill. Starting a race already knackered from pushing a bike that won’t start is not good.

Carbs will be VM28 with vacuum fuel pump.

Ignition will be HPI with two dual output coils.

Chambers will be of our design and porting will be conservative.

Over the last while I have been accumulating and making / modifying numerous small parts that are required.
Last edited:
The kick start shaft modified to enable remote start with drill and socket. The pall has been turned down and most of the spline removed so a nut can be pressed on, it needs to be welded still.

An assortment of reeds cut from fibreglass and carbon fibre have been made. I think we will go with the fibreglass ones cut from 0.4mm thick sheet initially. Fibreglass is hopefully a lot kinder than the 40 year old steel reed to a motor when it travels through it.


The standard reed blocks have been opened up and modified to gain flow. Further mods are to remove the centre bar and use a single petal reed if required. RZ reed blocks can also be fitted with work to the barrels.


6mm reed block spacers waterjet cut from Al plate. Setting the reed block back unshrouds the boost port in the air cooled A/C RD 350.
Vacuum fuel pump and primer bulb. The pump is rated at 65 litres per hour (1083 ml/min). A formula for fuel demand for a 2 stroke in ml/minute is the HP x 13. We are aiming for around 80hp that works out to 1040ml/min. So the pump is borderline but it will be easy enough to add another one.

Standard VM 28 carbs cleaned up and modified to Dave Friest specifications. RZ 350 carb mounts with balance tube bungs, one with vacuum take off for fuel pump.
The balance tube is to smooth out the mid-range. We will not be running in the mid-range so probably won’t need them.
We can experiment with using them if we need to. VM34’s work well on these bikes but we had the 28’s and I have read that they will be more than adequate for our bike in its initial state of tune (mild).

Unipod foam filters these are without the solid end. When setting up the frame you need the carbs air filters fitted so that you can make sure they don’t foul the frame and there is enough clearance for the rider.

Quick pull throttle and 1 to 4 splitter. The splitter started life as a 1 to 2 destined for an XS but I discovered it was pretty easy to convert to a 1 to 4. The throttle cable is push bike brake cable.

Ignition on/off switch (actually a light switch), tether switch a must for sidecars, hour meter to keep a track of service intervals, LED neutral light. The neutral light is a nice to have but not essential it will be powered from a 9V battery. It may not make it to the completed bike as we are trying to keep things as simple as possible, less to break down and cause problems at the track.

Mitaka RZ 350 pistons modified to suit the air cooled motor. The tang on the rear skirt is removed. RZ pistons have larger port window than air cooled pistons. These will be carefully sanded to reduce stress risers and the crowns and skirts coated before final assembly.

RD 400 head gaskets I thought these were copper but they are only copper coated ferrous metal.
RD 400 head gaskets have a larger area than the standard RD 350 ring; the barrels need to be machined to suit. The larger area provides a better seal and is less likely to the leak and allows higher head nut torques. Further developments may include machining for O rings if the engine holds together. For now once we know how thick they need to be we will cut from copper stock.
"Copper gasket held by magnet"

Water jet cut exhaust flanges machined to suit spring mounted exhausts.
Hinsen Billet proof clutch, straight cut gears and clutch damper. The damper should mean we don’t need a rear wheel damper like the XS outfit.
The straight cut gears will reduce axial loading on the 4 pot crank.
FZR 600 plates have a larger surface area than standard RD ones and we may be able to fit an extra plate as well. EBC heavy duty clutch springs.
An assortment of stock steels have been bead blasted and the best ones will be used.

Hydraulic clutch slave cylinder, clutch spring adaptors and home-made clutch holding tool.


Engine side covers bead blasted and burnished with scotch bright.

Crank wheels cleaned and lead weights repressed to ensure tightness.
Engine work

Initial lining up the cases to check what needs to go and what can stay.

And so it starts a few pics of machining the cases.

2017_0612fireplace0014comp.jpg 2017_0612fireplace0017comp.jpg

Machining the alignment bars, 62 mm diameter 480mm long as close to perfectly parallel as I could do. Had to make a lathe dog and watch lots of YouTube to learn how to do this. It was pretty scary having such a large piece in the lathe.


First bar fitted.


Second bar fitted


Machining the centre barrels.

Slapped together for motivation and a few pics.
2017_1211fireplace0001comp.jpg 2017_1211fireplace0002comp.jpg 2017_1211fireplace0003comp.jpg
Machining a block to mount the cylinders on the mill so that the gasket ring can be machined off suit a RD 400 head gasket.

Taking a resin cast of the stock combustion chamber.

Head mandrels for squish band cutting, head centralisation, polycarbonate plate for measuring head volume have been made. Still waiting on the burette to arrive.


Using the head centralising mandrill. Note the fin cut off the head, this will be repaired.

Once secured central to the bore the head will be drilled and dowelled to the barrel. On a standard Rd there is a lot of tolerance in the head bolts and it is a lottery if it aligns as it should.
2018_0723fireplace0011.JPG 2018_0723fireplace0012.JPG
More work on the running gear. Skimming the wheel hub surface it just fits in the lathe.

Drilling the rear brake carrier/ hub half.
2018_0827fireplace0004.JPG 2018_0827fireplace0005.JPG

The chain adjusters almost finished, if they look familiar they are my take on the Ducati TT2 units but scaled up a bit.

Working out the size of axel spacer needed for the rear calliper holder. It is a XS 650 rear unit drilled to take a 25mm axel.

More work required to adapt car wheels than you would think, bushes for the wheel stud holes to suit the hub bolts.

Yet more work, inner bearing spacer.
Brakes and suspension.

YSS shocks longer ones for the front and shorter for the rear.

XS 650 disc drilled and bead blasted some have been resurfaced by a precision grinder. We are going to try using three of these with two callipers on a single front disc and one each on the rear and side wheels. The front hub is made to take a second disc if the 2 on 1 idea doesn’t work.
2017_0108fireplace0006 comprss.jpg

XS callipers cleaned up new aluminium pistons made. These are considerable lighter than the stock ones.
stock compressed.jpg ali compressed.jpg

Stock brake piston 189g, Al replacement 64g. 125g x 4 =500g saving.
Last edited:
Max Pete thanks for the compliment.
Thanks 2M, will put that into the mix of ideas.
Everything we have thought of so far has been over complicated and fussy. It may take several attempts to get the one we go with but that's the way this sort of stuff goes, rarely is the first idea the best.
Got a bit more work done on the rear axel and swing arm. Finished the chain adjusters. The tubes look heavy but are thin walled so hopefully they will be strong enough, we can always brace it I suppose.
The extra length behind the axel is to fit the shock mounts. In the photos the adjustment is at its most forward position.
I have not been able to find many options for 25 x 1.5mm nuts so got some stainless ones of ebay and fitted some pins to enable a split pin to be used.
I wanted to use 25mm to maintain as much wall thickness in the hollow axel which is made from heavy duty hydraulic tube.
The whole set up has me thinking it is pretty wide at the axel but it can be narrowed up at the pivot.

Looks like we will probably be running 2 discs up front as on another outfit my collaborator built for his kids he experimented with 2 calipers on one disc. Initial results are that fade is a problem. We assume this is due to heat however I don't know what pads they are using and the discs are not cross drilled so could be ok just needs further refinement.
2018_1007fireplace0001.JPG 2018_1007fireplace0002.JPG 2018_1007fireplace0004.JPG
Last weekend 1000 cc Nortons were finishing at least the length of the start finish straight ahead of us.
I returned to this bike with new energy.
Thinking about the rear chain adjuster set up, it is too wide so have put them aside for a possible future project.
I have now made more conventional helix shaped adjusters that will end up with a narrower rear end.
We were going to use XS ones and bore them to take the 25mm axel but the ones on hand look pretty average and the new ones look better and are lighter, its nice to have a win .
The ignition has arrived and a Schitsu tacho is in the mail.
There are programmable ignitions available but we don't want to add complication, at this stage simple is best.
Apart from tyres most of the expensive parts are in hand, however I tried to get some gearbox bearings today. No joy locally as they all seem to be specials.
The cluster also looks pretty tired so will need to source one in better condition. A Nova gear set is too expensive.
Tomorrow I will start making the slotted plates (fish plates ?) to carry the rear axel on the swing arm.