Yamaha RD400F Restoration

Yamaha RD400F Restoration

RD400FDave Newitt, from Hinckley in Leicestershire, has a history of restoring old XT Yamaha’s but has recently turned his hand to a string of smaller capacity strokers. His latest being a relatively rare 1979 RD400, and the last of the air-cooled breed before the world went totally LC crazy.

Better known as “Thumper Dav ” a nickname gained from his track record restoring & showing his XT4500 projects, of late his interests have taken a turn, albeit remaining firmly in the Yamaha camp. His passion for restoring bikes started back from when he was a teenager, with only a few spanners in his tool kit. “Times were hard when I was a younger” Dave states “but it taught me all my restoration skills the hard way”. Now aged 46, married, and with 2 children, his interest in getting bikes back to as new condition hasn’t diminished.

Yamaha RD400FMany years ago, Dave started buying Yamaha’s from the 70’s & 80’s period, to restore and sell on to raise funds to fund his biking interests, this progressed into building one off custom classic bikes and restoring bikes for a few select friends and customers. Although Dave prefers his 4-stroke bikes, he has a huge passion for the early two strokes. “I wanted an RD400 when I younger, and I knew that if I wanted one now I’d literary have to make one out of a basket case due to the rising costs of tidy examples”. His present collection of bikes consists of, 1979 Suzuki X7 and a 1980 RD350LC, all bought on the cheap and restored by himself. Dave’s considers himself to be one of the few remaining UK restorers that actually does the work rather than just stripping a bike and sending off the parts to a variety of suppliers and trades people only to be assembled as new later on.

In simple terms, Dave makes everything and does everything wherever possible, if it doesn’t fit he will make a new one. “Being self-sufficient and armed with the required skills, means I can now fully restore a bike within 4 -6 week period” he states. Dave’s many talents include Painting, fabrication, zinc plating, blasting, welding as well as all carrying out all of his own engine work. He has been known to fabricate his own seats covers too, when his wife lets him use her sewing machine that is.

Today Dave offers his services and advice to those interested in restoration work via his own website www.yamahathumpers.com.

Yamaha RD400 Restoration“My search for the right RD400 took me 2 years in total, fuelled by me owning one many years ago and like most, wishing to re-live my youth in a cloud of 2-stroke smoke. The bike was sourced via eBay, bought using the “Buy It Now” for £1.400.00, having had just 2 former keepers, and as a bonus, all of the old tax discs & related Mot’s to warrant the genuine 12,000 recorded miles were present and correct. It was exactly what I was looking for, having been stored inside a wooded shed for the last 17 years, and covering a total of just 2,000 miles in that period, mostly accumulated taking it for its annual Mot over this period. Having got the bike back to my workshop, I could have a better look around it and overall the bike had seemed to survive quite well. However, a closer, in depth, examination revealed more issues and additional un-planned work. The frame was rusty everywhere and the paintwork was very tired and damaged, so my decision to completely strip the bike down commenced. This generated a huge pile of rusty black metal bits, which were swiftly shovelled into the back of my car, destined for sandblasting and powder coating at KMH powder coating of Leicester.

Yamaha RD400F engineDoing this freed up valuable floor space and permitted me time to inspect all the others components closely. By pure astonishment, most of the original items required nothing more than a good clean up. The wiring loom only required a few new terminals, which I replaced, while all the switch units and clocks were excellent underneath the years of grime and dust. Most of the original nuts, bolts, fixtures & fitting were corroded badly, and not seeking to cut corners I re-zinc plated everything. The bikes original chrome work required nothing more than good polish, I was amazed at this as Yamaha chrome of the period isn’t rated as being the best at longevity, normally the RD400 suffers quite badly in this respect, and this find was a big bonus. With this unexpected saving, I thought I’d treat the underside of each mudguard to prevent future corrosion ever setting in later on. Having thoroughly inspected & cleaned everything removed from the frame, I’d now accumulated quite a large list of new parts required for the rebuild, something which Granby motorcycles in Derby assisted me with.

Yamaha RD400The paintwork was showing it age, wearing a large yellow fuel stain on the top caused from a leaking petrol cap seal. Having restored many bikes over the years, experience leaves me no option but to paint stripper the lot and repaint everything. Anything less would have resulted in different shades of white, something I wished to avoid. Once stripped of paint, the petrol tank revealed light surface corrosion underneath and evidence of an old repair on top of the tank. After repairing and painted everything back to original spec, I applied new decals as per the original design.

The seat was in excellent condition but the cover had perished, so I got away with only required a new seat cover to which I fitted myself having sourced from a guy that makes them for the VJMC club. Both the wheels were paint stripped and brushed painted “Pillar Box Red” sourced from my local £1.00 shop. The brakes were fully stripped and re-painted; I even re-plated the original brake hose fittings. Having completed all the chassis components, I turned my attention to the engine. The engine ran, and performed, very well before I removed it, so I wasn’t expecting to do a great deal of work once inside it.

RD400F engineI decided to sand blast both cylinder barrels and heads, as the original paintwork was flaking off. Paint stripper was applied to all the engines outer casings and a thorough clean out of the engine internals was carried out. The engine, having covered few miles during its life was in great condition and inspection failed to reveal any internal faults or measurable wear. As gesture of good will, I treated the engine to a new set of pistons and rings, bought for a staggeringly cheap £20 each from the Donington Park classic bike show last February, to its still standard bores sizes. Assembled with new gaskets and fitted with its newly painted outer covers, the engine was beginning to look really nice. To cosmetically enhance the engines appearance even further, I removed and re-zinc plated all the original engine bolts/brackets and mounting so to look new again. Both carburettors received the similar treatment being fully cleaned and re-built inside and out and now look and work like new. Wherever possible new parts where used for the consumables areas like the reed valves and carburettor rubbers.

One week later the powder coating is completed and ready for collection. New taper headrace and swinging arm bearings were used to re-assemble the bike. I’d strongly advise to anyone powder coats a motorcycle frame to ensure you run a clean tap through all the threads or risk discovering after you’ve built the bike up that damages threads lurk within. With all of the parts now back in my workshop huge pile of black shiny metalwork looking at me, it was now time to build the whole bike back up. Assembly was a fairly straightforward task and greatly assisted by the numerous amounts of pictures I’d taken during the restoration.

Problems encountered:

1: Locating the correct rear brake link, as someone had fitted the wrong part.
2: Fitting the new pistons back into the cylinder bores, rings fouled on inlet ports requiring the reed valve blocks to be removed to gain access to the rings.
3: Front engine mounting bolts were a nightmare to insert, especially with the rear bolt in place, apparently this is normal but I did fear a bent frame at first.
4: Fitted a new throttle cable and with the first twist of the grip the cable snapped.
5: Clutch adjuster inside left cover had seized up.

Granby motors, tel 0115 944 1346
KMH powder coating, tel 01162 770 050
Classic restorations, tel 01455 440 604

1979 RD400 4L0 Specification

  • Type Air-cooled twin-cylinder two-stroke
  • Capacity 398cc
  • Bore x stroke 64 x 62mm (2.52 x 2.40 inches)
  • Compression ratio 6.2:1
  • Fuel System Mikuni twin 28mm VM slide carburettors with reed valve induction
  • Primary/final drive 2.869, Chain, (17/38)
  • Clutch/gearbox Wet multi-disk /6-speed close mesh
  • Electrics 12V 5.5ah, CDI electronic ignition
  • Frame Tubular steel
  • Front suspension Kayaba 35mm oil damped telescopic
  • Rear suspension steel swing arm with twin oil damped shocks
  • Brakes front/rear 267mm disc with single-piston floating-calipers
  • Wheels front/rear Cast Alloy 3.00×18 3.50×18 inches
  • Tyres front/rear 3.60 x 18 Dunlop TT100 4.10 x 18 Metzeler Perfect Me77
  • Dry weight 174 kg (385lb)
  • Wheelbase 1334mm (52”)
  • Seat height 800mm (31.5inches)
  • Fuel capacity 16.5litres (3.63gals)
  • Top speed 108mph
  • Max power 42bhp@7500rpm
  • Fuel consumption (claimed) 35mpg
  • Price new £ 980 inc vat (1979)

Daves top tips for RD restoration
Never let your heart rule your wallet when it comes to buying that ideal bike.

You’re better to paying more money for right bike, than having to source all those no longer available parts from Yamaha.

Be methodical and keep a written record of what parts you require and what exactly you aim to achieve.

Take good, clear pictures of the bike before the restoration, and during the strip down will save time wondering where all those parts go, this is doubly so when dealing with wiring.

Expect to pay high prices for bikes with matching engine & frame numbers/ history & low mileages.

If matching numbers don’t interest you, you’ll still achieve beautiful restored bike for far less money.

The RD400 was pretty much a solid bike, but suffers from corrosion in most areas un-seen.

Items such as the frame/ fuel tank and the steel seat base will no doubt require repairs.

Sticking brake callipers/ worn swinging arm bushes, over bored engines & worn out engines are almost guaranteed.

Yamaha RD400F Gallery

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