Bought on impulse for £350 this Honda VFR400 NC24 had obvious accident damage and was in poor cosmetic condition. The intention was just to get it roadworthy with a minimum amount of work.
Apart from a bent subframe and badly damaged fairing this Honda VFR400 NC24 looked complete and straight. The exhaust was badly corroded and I’d wrongly assumed that if it was too bad to weld I could get a used or new replacement. I hadn’t done my homework, firstly it’s a discontinued part and decent second hand collector boxes are almost impossible to find and command a premium. Secondly it’s not possible to remove / replace the collector box and exhaust pipes without removing the engine from the frame.
The NC24 model was intended for the Japanese domestic market only and consequently there’s little printed material in English. Fortunately there is a lot of information online, especially the 400Greybike forum and Honda VFR400 NC24 & NC21 Community Facebook group. This particular bike is 1988 Honda VFR400 NC24 RJ-III and had arrived in the UK during 1994 via the grey import specialist BAT Motorcycles.
The engine had to be removed to replace the collector box and it was at this point it developed into a restoration project. The frame and subframe were powder coated metallic silver. The engine required little work other than replacing the water pump due to corrosion and setting the valve clearances. Unlike the later NC30 model which uses shims to adjust valve clearances, adjustment on the NC24 is by a screw and locknut. Its simple, very quick and easy! The covers were powder coated black.
The carbs were removed, partially stripped and cleaned. The jets, emulsion tubes and float needles were all replaced. Float heights were all over the place and I set them as near as I could to the standard 6.8mm. The old carb rubbers had hardened with age so they were replaced with new. Initially, reinstalling the carbs was a real challenge. I’ve since found the best way is to use a light smear of red rubber grease and secure the front rubbers to the head. Next place the rear rubbers partially on the head at an angle. Push the front carbs into place and as they slide home push the rear carbs into place. There’s definitely a knack to it and it works just the same on the 750 too.
The electrics were in good condition except for the HT leads and plug caps which were past their best. The correct caps were hard to find. Eventually a new set was sourced from NC30/35 specialist Rick Oliver who can also supply some NC24 parts. The entire wiring loom was checked for damage and all connections carefully cleaned as some were showing slight signs of corrosion. The stock regulator has a poor reputation for reliability and R6 regulators seem to be a popular alternative. Fitting details are well covered in the 400Greybike forum. The regulator was a tight fit and I had to file two channels across the fins to make room for the ht leads which are routed below it.
The polymer bush on the fork anti dive mechanism had worn but was I unable to source a replacement – another discontinued NC24 part. The hardened steel piston collar (also discontinued) which fits inside the bush had cracked causing it to be slightly wider where the snap ring fits. I’ve also seen this in two other collars which were among some used spares I bought. Searching online I found plain bronze bushes (8x11x8mm) at £7 for a pack of 5. It was an easy job to press out the old worn plastic bush and fit the bronze bush.
For interested metallurgists out there, chemical analysis revealed that the collar had been produced from a free cutting steel with a nominal composition of 0.42% carbon, 0.23% sulphur and 1.0% manganese; the surface hardness was 55HRC. High machining rates are achieved during production by using free cutting steels but this is at the expense of ductility and toughness, undoubtedly compounded by the high hardness. I’ve since had some replacement piston collars machined from Uddeholm THG 2000, a high strength special steel, prehardened and tempered to 40HRC. I’d expect this to be a significantly more crack resistant than the free cutting steel originals. Please note that this modification is the way I carried out the work and should not be understood as the official or necessarily the correct way.
Fork servicing can be tricky if both legs are dismantled together and the parts mixed or if they have been previously reassembled incorrectly. Some internals of each leg are different and unfortunately there isn’t an English manual. However they are very easy to work on and it only needs a few minutes study of the online parts microfiche or the Japanese parts and workshop manuals. Firstly the stanchions are different lengths and the shortest fits in the antidive leg. The oil dampers are different too but are easy to identify from the microfiche. The source of most confusion seems to be the alloy oil lock piece which should fit on the antidive side with its flange down. Again this is clearly shown in all the microfiche and Japanese manuals but many seem to assume this is a printing error and install it the other way. The fork springs are installed with the tightly wound section uppermost.
Initially, the panels and a Skidmarx fairing were painted by Dream Team in the Lucky Strike colours. Over a lengthy period of time I managed to collect a full set of original plastics and a tank. These are becoming increasingly hard to find in decent condition and I had to bid for a couple of panels on the Japanese Yahoo auction site to complete the set. Paintwork was carried out in original colours by Hull based Rapier Paintwork.
The build was featured in the August 2018 issue of Practical Sportsbike and during the photoshoot, motorcycle journalist Simon Hargreaves experienced some unnerving slides on the bike whilst cornering. NC24 forks are known to be soft and I sort of accepted it. I’d fitted a Hagon rear shock during the build to replace the original worn out unit (I’m currently refurbishing a standard rear shock to get the bike as near factory as possible).
The forks were standard, just as they left the factory. After a short discussion we felt that whilst it was ok for me, it was too soft for Simon and that the forks would benefit from a spring upgrade. Other NC24 owners have fitted Maxton springs with good results and I’d previously spoken with Maxton. The following week I ordered a custom set of springs and spacers based on my weight. Turnaround time was quick, the spacers were neatly machined aluminium versions replacing the awful cheap sheet metal efforts fitted by Honda. Although I expected an improvement in handling, the transformation particularly under braking, was huge.
In contrast the popular 90s magazine, Grey Bike generally praised the handling during its road test of a 1987 Honda VFR400 NC24. I guess that’s both a reflection of suspension at the time and relaxation of the springs over 30 years or so.
Decent suspension helps here and despite the relatively firm setup of the bike I rode, the suspension remained compliant enough to soak up bumps and road irregularities… The front end makes do with a set of conventional teles adjustable by means of air valves, and these do a great job keeping the front end under control, especially when pulling hard on the pair of two pot Nissin Calipers…..Grey Bike magazine Summer 1995
Grey Bike magazine Summer 1995
Parts availability.
Some new and aftermarket parts can still be obtained from cmsnl, Wemoto and David Silver Spares. Additionally Rick Oliver, although a Honda NC30/35 specialist, can also supply some parts. Many NC24s have ended their lives at the breakers and there is a large used spares market. However certain items are becoming increasingly rare in good condition and you can expect to pay a premium! These include:
Petrol Tanks
Collector boxes
Petrol taps with filters
Gear levers
Air intake snouts and frame retainers
Genuine fairing panels
Printed Resources.
As I mentioned earlier theres very little printed material in English for the NC24. There are a few pages of NC24 specifications and torque settings appended in the Haynes Service and Repair Manual for the later, and very different, NC30 and NC35 models.
The Japanese Workshop Manual, Part List book and Riders Manual are all usually available on the Japanese Yahoo auction site. I used Buyee Japanese proxy service. The site is also great for hard to find parts, but make sure you read the excluded parts list for shipping. Alternatively some files are available for download from 400Greybike forum and the Honda VFR400 NC24 & NC21 Community Facebook page.
Workshop manual for Honda VFR400 NC21 and NC24. Text can be translated using apps such as DeepL.
Parts list book for Honda VFR400 NC21 and NC24 models.
Front and back pages of Honda VFR400 NC24 sales brochure.
A.M. Photoblog 