The Modification of " Green Bean "

" Green Bean " is / was a Yamaha RD400 Daytona from 1979 for the non-historians (like me) she was originally white with red and black decals and electronic ignition as standard.

I found her in a chicken run looking very sad and took here away from her 'Sh**' covered life for the measly sum of 500 local dollars. (She & I met originally in the West Indies) about 200 UK pounds in those days. I scrubbed here down thoroughly, then preceded to strip her to the last nut and bolt.

Engine modification

The engine was standard so the rings got replaced. The ports were altered as follows:-
Exhaust port = 188 degree
Transfers cleaned and the bottom opening into the crank area knife edged and thoroughly smoothed.
Inlet port widened by 2mm
The piston bottom edge was filed to give a 2mm wide wedge to help the oil on the cylinder wall get squished up between piston and the wall rather than be scraped off and be allowed to run down into the crank area.
Whilst on the subject of the piston modifications I open up the oil holes in the underside of the wrist pin bosses and enlarge the countersink to them. The Piston port should be re-worked to match the inlet port outline. Please be sure to round off all the edges inside and out to this hole in the piston.
For this state of tune I used Expansion Chamber from Allspeeds for the YPVS model RD 350 and if memory serves lengthened the centre barrel.
The carbs are YPVS model 31K fitted out with:-
main jet 250
Jet needle 5k1 fitted in 4th position.
Needle Jet P - 0
slide 2.0
Pilot jet 30
Start jet 70
air filtering is with single K & N's per carburettor and stock reeds or Boysen f'glass for the RD400F. During my time as a Yamaha service provider I found several stock Air Boxes wrongly assembled with the bikes having rather a sluggish power range.(THIS WAS STRAIGHT FROM THE FACTORY although I did find the odd one on weekender mechanics bikes as well !!!)

The spark plugs are B9EV (these plugs have fine precious metal central electrodes and by my experience at least less prone to fouling and generally 'dodgy' spark production)

Frame Modifications

On this model RD400 the footpegs are on a frame loop just rear of the swingarm pivot. These loops were cut off inline with the frame re-enforcement plates. There are two original stubs fitted each side of the frame at this point on the plates. I made plates, from 10mm Aluminium plate stock to carry the rider and pillion foot rests (also acts as a fixing for the rear bracket on the expansion chambers), that slid over these stubs and secured in place by very thick washers fabricated from aluminium bar. (SEE PICTURES ON MAIN GREEN BEAN PAGE)

On the Left side one of these stubs can be used as a pivot for a rear set gear change pedal and linkage (my original version was a bolt on from the YPVS model).

On the Right hand side the rear set rider foot peg puts the brake pedal pad section too far forward of the rider's boot. I cut off the pad section and heated the bar section to BRIGHT CHERRY RED heat and bent it at right angles for the last 1.5 inches from the freshly cut end.--- BE AWARE THAT THIS MATERIAL MUST BE BENT AT BRIGHT CHERRY RED HEAT anything less than this will cause stress cracks in your brake lever !!!!!! DO NOT chill this material in water or oil ALLOW IT TO AIR COOL !!!!! for the same reason. I then arc-welded the pad back on over the bent bit.

The rear swingarm was removed and re-inforced with 1 inch square section tubing that was welded at the axle bearing end plate of the round section of swing arm on the RH side sloping earthward to meet a central 2 * 1 inch section tube spigot(in line with the tyre centre line) round and up to the round section of the swingarm on the LH side close to the axle bearing plate.

Whilst this added rigidity it allowed very little room for the chain to pass in the event of less than stella chain maintenance. (SEE PICTURE OF ORIGINAL ON GREEN BEAN TITLE PAGE)

The rear Fender as all steel fenders go was a piece of iron lace so I cut off the rusty bit and welded on another bit to act as a mud flap / Number plate holder. Since the plastic 'toolbox' was shot I made a steel one that was lockable and could act as rear lampholder as well. Most of the seat pan was fine but the lock had been forced at some point so it was replaced by a rally car hood stud and grenade pin type lock set-up.

©  Geo of K.G.B. of T & T.