Production Racing YAMAHA RD400

Originally bought from Cooper Brothers Motorcycle Shop on Templehill, Troon. Good straight out of the wrapper but its never enough is it ;)

Thanks Jim Paxton for the pics!

First things first, let’s get a bit more feel in the braking department, Aeroquip brake hose front and rear with Ferodo H pads, and thanks to my biking chum Geraldo original discs drilled to try and dispel water build up when it rains, which it does with monotonous regularity in the West of Scotland…

Braking now just peachy but also causing the front end to dive like a Kamikaze so cheap ‘n cheerful solution GTX Engine Oil instead of regular fork oil. I did try and cram a set of British Valve springs in also as dual rate spacers but that was a no go, front suspension went rock solid… Rear suspension taken care of by a set of Girling Norton Commando shocks a bit unforgiving on such a light bike but gave plenty of clearance for leaning over on the twisty bits.

Rear-sets and drop bars followed with the obligatory hacking off of extraneous material from the rear-sets. Drilling the sprocket cover and any other non-structural part seemed like another wizard idea in the quest for better power-to-weight ratio obviously both centre and side stand were deemed non-essential so off they came. An OW31 seat took care of the derriere department which remained unpainted for the duration with fibreglass front guard rather than cut down the original metal component, obviously fork rigidity was not helped when attached by jubilee clip, so not a great idea.

Fortuitously American Cycle Magazine ran an article describing in detail how to tune Yamaha twins so off we trundled to Dave Hanvey’s garage to pull the heads and barrels and see what was what. Transfer ports were polished to a razors edge and opened up to the base gasket mark so nice flowy fuel mixturey bit. Piston windows were also reworked so, all in all, a lot crisper and more responsive as was proved when outdragging a DRM of Kirckaldy tuned RD 350 along the straight at Knockhill in the Open Production Class. The oil pump was ditched in favour of premix for a lighter Quick Action throttle but was a actually pain to have to carry about a bottle of Bel Ray Two Stroke when out for a run down the Coast.

Kawasaki adjustable Steering Damper was eventually fitted with removing a bit of the Head cooling fins and that was it…happy days.