NS400R Engine Rebuilds, Servicing & Conversions

Engine Rebuild Service

We offer a full engine rebuild service for £475 plus parts. Please contact us with your requirements for a more detailed price.

Engine Conversions

Honda stopped production of many major parts for the NS400R almost 20 years ago. As most engine parts are almost impossible to get hold of the use of alternative quality aftermarket parts is often the only option available.

Most 20,000 mile bikes will require re-plating of the cylinders (£150 each, please ask), new pistons and the crankshaft rebuilding. High quality Japanese 57mm piston kits are now available (56mm for South African model & NS250R, MC11) in the engine parts section, to replace your old worn out pistons, beware of cheap imitations on ebay for £50 per set that don't fit!

Here at Classic Race Replicas we have developed 475cc & 444cc big bore kits using 63mm & 61mm pistons priced at £1800 & £1725. Your old barrels and heads are required for this conversion or if available supplied at an extra cost of + £250. A deposit of 40% will be required upon order and will take up to 12 weeks before completion.

We also offer a full range of engine tuning for the NS400R, including - Head skimming / re- squishing & O-ringing.
Cylinder Inlet & transfer mods.
Alloy cylinder base gaskets to raise the exhaust and transfer.
Carb boring standard 26mm to 28.
Standard exhaust gutting.
Race fibre reeds.
Aluminium end cans.
Dyno tests of the above mods gave an increase of 10bhp over standard. Dyna Pro dyno reading not the high reading old dynojet dyno's give (add +5bhp to all figures quoted if dynoed on dynojet dyno) Cylinder tuning, road or race.
Mild road tunes (387cc) 62bhp - 34ft/lbs tourque at rear wheel (standard is 55bhp on a good UK spec bike, not 72 as Honda claimed!)
Race tune 63 - 66bhp - 36ft/lbs torque at rear wheel or 72bhp with pipes (please ask).
444cc big bore, 75 - 82bhp 43ft/lbs torque depending on pipe, carb & ignition combination.
475cc big bore, 82 - 88bhp 46ft/lbs torque depending on pipe, carb & ignition combination.

More power still if you want to go racing, let's go for it!!

Reconditioned Crankshafts

 All reconditioned crankshafts have new big ends, main bearings, come with a full set of crankshaft seals fitted and are fully balanced. Con rods are good used and all webs are as new.

Non-exchange cost is £950 (available to purchase in the parts section) or £775 on an exchange basis for a faulty crankshaft, dependent on condition (please contact us to arrange). Please note, customer is responsible for any shipping costs to send a faulty crankshaft to our UK workshop.

Wheel Conversions

In 1985 the NS400R was at the height of technology and was announced to be the best handling bike of its day. 31 years on its still a great bike, however tyre technology has moved on to a different level as have wheel diameters and widths. Here at Classic Race Replicas we have developed a variety of wheel options so you are able to fit modern tyres to your pride and joy.

Rear Wheels

17” x 3.5” Comstar (please ask)
17" x 4.0" 3 Spoke
17” x 4.0” 6 Spoke 

Suitable for tyres from 130 to 150 by 17”.
Example of 17” x 4.0” Rear (Option H) below suitable for 140/150 tyre (150 max in standard swinging arm)

Front Wheels

17” x 2.5” Comstar (please ask)
17” x 2.5” 3 Spoke
17” x 3.5” 6 Spoke

Suitable for tyres from 110 to 120 x 17”.

Please contact us for prices and availability.