ENGINE

2003 Fuel Injected Yamaha R1.

A new fuel injection system was introduced for the 2002 year, which worked like a carburetor by employing a CV carburetor slide controlled by vacuum created by the engine. With a similar power output to the 2001 bike, the engine was developed (larger bore, shorter stroke) to rev higher, faster and for longer. This engine should be good for approximately 150bhp.

ENGINE FRAME

From the outset we wanted to retain as much of the original mini subframe as possible.  This not only reduces the amount of fabrication time for mounting the engine, but also makes the frame more viable if the build is replicated in kit form.  The only modification made to the stock subframe is the removal of the front cross member to allow for the exhaust header to fit inside the flip front.

Our bespoke frame was initially produced in 20mm tubular steel, but after discussion with James, we both agreed that something more substantial would be more suitable.  The frame pictured is made from 27mm tubular steel and consists of 3 parts welded together.

There is the rear hoop which connects at the bulkhead and at the stock R1 engine mount points.  Then the front down struts were bent to shape and then tacked in place.  These connect to the front corners of the stock mini subframe using bushed housings which have a peugeot 205 tie rod bush installed on each side.  The reason for installing bushings has been to absorb engine/transmission vibration and to reduce side loading on the frame under acceleration/braking. 

The rear hoop of the frame also serves the purpose of hanging the diff cradle (cradle mounts pictured right).  We wanted to hang the diff from the engine and not connect it to the chassis in any way as movement of the engine unit under load would affect chain tension. 

DIFFERENTIAL

The differential unit itself is a bought item and can be sourced directly from quaife, swift tune or from bj auto bits in the UK which is where I purchased mine.  The ATB diff is geared, not plated, and such items are popular for kit car builders as plated diffs can often be too aggressive.  I run a plated LSD in my suzuki swift rally car, and it works extremely well, but the torque steer is quite severe and therefore the car isn’t ideal for daily road use.  I hope this project results in a mini which can be used on the road without giving the driver too much hassle.

The modifications for the differential unit in order to fit it to the bike engine involve housing the diff, containing oil for lubricating the diff, supporting the diff and tensioning it.  For the housing we created a pair of bearing blocks (pictured) from aluminium stock purchased on ebay.  These blocks will house the LSD main bearings on one side of each block and the stock mini, driveshaft oil seals on the other side.  The blocks also requiring mounting holes to accept retaining bolts for the diff cradle which will hang from the engine frame via rose joints (pictured). 

To lubricate the diff, we will fabricate an oil can which can be either glued on or bolted to the diff face.  Then by installing a drain plug/filler hole/grease nipple, the diff can be oiled or greased respectively. 

For the diff tensioner, we will design a framework which will attach to our main engine frame and from this we can install a worm drive or tensioner rod which will drive directly into the bearing blocks or diff cradle.  This drive/rod will be adjustable so that the diff cradle can be pushed towards the bulkhead to give chain tension as the diff will swing from its rose jointed mounts above.  This is one of the most important parts of the build as chain tension is crucial for maximum performance and also for the longevity of the chain/sprocket. 

GEAR SHIFTER

The gear selector is what I consider to be the centre piece of the build.  Rather than retain the stock mini gear shifter position from the floor pan, I wanted to go for a more WRC style shifter mechanism to add another unique touch to the build.  It also means we can mount some of the switch gear in the floor pan where the original selector resided to keep the weight low in the car. 

The first part of the shifter (top picture) is a boss which clamps around the stock mini steering column.  From its mount position, the shifter can then tilt forward and aft about the rose joints on the shifter boss. 

From the in-car part of the shifter, we will install a nylon rod directly through the bulkhead on to a pivot/bell crank setup in the engine bay which will control the stock R1 gear selector (pictured bottom).  The gear selector mechanism has all been fabricated from steel or aluminium and incoporates rose joints to provide a simple but effective means of changing gear. 

This part, like many of the other bespoke parts on the mini, have been made with limited resources and basic tooling, and with the view to possibly re-producing the gear shifters as part of a kit.  The fact that the shifter is adjustable means we can alter the throw and the overall feel of gear selection so that the driving experience is as good as possible.