Honda VFR400 NC24

I got my Honda VFR400 NC24 after my wife spotted an ad in the local shop window. Within an hour I was checking it out as I wanted a project for the coming winter evenings. It was a 1988 VFR400RJ-III (NC24) and I was disappointed that it wasn’t the NC30 model. It was really scruffy and had some road rash but at £350 I thought that I would be able to tidy it up reasonably cheaply. The battery was flat but I was assured that it ran ok so I returned with a trailer and it was in my garage the next day.

Back home, under the lights it didn’t look so good. Undaunted I removed the panels, fairing, seat and tank to have a good look. I noticed that the rear sub-frame was bent, somebody had dropped it in the past and this part had taken the brunt of the impact. Fortunately everything else seemed to line up ok. The next thing I discovered was that the exhaust collector box had completely rotted but I figured (naively!) that I would be able to weld it up or if it was too bad then I’d get a replacement. I hadn’t done my homework, firstly it’s a discontinued part and decent second hand collector boxes are almost impossible to find. Secondly it’s not possible to remove / replace the collector box and exhaust pipes without removing the engine from the frame.
The only option was a complete strip down after a thorough search online for information. One of the first sites I found was the 400Greybike forum which stood out from the crowd. There were also some very good enthusiast sites with excellent "howto" articles. I should have read these first and then I would have been in a better position to haggle a little more. There's little printed material (in English) available for the VFR400 NC21 or NC24 models and without doubt the forum is the first place to start.

In a short time the bike was completely dismantled, cleaned, degreased and the parts sorted into plastic storage boxes with a photographic record particularly of the wiring for future reference. That was the easy bit.

neglected VFR400 NC24
Plenty of siezed bolts
Badly corroded NC24 collector box
Rear hub evidence of crash damage
Bent fairing bracket crash damage
NC24 Engine poor cosmetic condition
The exhaust collector box was too badly corroded to weld and a replacement was impossible to find. The odd one appeared on eBay but they all looked to be in poor condition. Eventually I discovered MLB Manufacturers in Taranaki, New Zealand who were manufacturing copies and I bit the bullet and ordered one. The fit wasn't perfect but it was a good starting point and did the job. Since then, David Silver Spares have started selling replacement copies in stainless steel which can be fitted with the engine in situ - just my luck!

A replacement sub-frame and various other second hand parts were bought mostly on eBay. It made sense to routinely replace bearings and seals for the steering head, swing arm, linkage and wheels and these were obtained from Wemoto, Lings and David Silver Spares as were any necessary gaskets, fasteners etc.

Having gone this far I had the frame, wheels, brake calipers and various brackets shot blasted and powder coated. Most of this work was carried out by Triple S Powder Coating in Bingley. Prices were a little higher than other powder coaters but you definitely get what you pay for, the quality was fantastic. The calipers were fitted with new stainless steel pistons, seals and pads. The rear shock was in a terrible condition and past reconditioning so a new Hagon replacement shock unit was purchased.

The inlet rubber mounts for the carburettors were rock hard and cracked so new ones were fitted. There’s definitely a knack to fitting the carbs on the rubbers. It seems to need a disproportionate amount of brute force and swearing before they suddenly and almost magically slide into place.

While searching around the 400Greybike forum I found details of the hydraulic clutch modification for the NC24 which seemed worthwhile. A VFR750 master cylinder, NC21 hydraulic slave unit and sprocket cover were all found on eBay. The pushrod was a little harder to find and eventually I obtained one from a 400Greybike forum member - thanks Neosophist. Fitting was simple and the clutch action is light and progressive.

The electrics were in surprisingly good condition except for the HT leads and plug caps which were definitely past their best. A new set was hard to find and eventually I got some made up with some nice plug caps by Rick Oliver. The entire wiring loom was checked for damage and all connections carefully cleaned as some were showing slight signs of corrosion. There was some discussion at this time on the forum that some benefits in fuel economy, tick over and starting could be achieved by adding additional earth leads. I was sceptical about this but as the frame was freshly powder coated and I reckoned it could only do good I added additional earth leads to the front coils, rear coils and the starter motor. Unfortunately I cannot claim an improvement as I never ran the bike before the mod other than to say I have no issues with the electrics.

I decided to replace the fork seals and bushes and whilst stripping them I discovered some surface damage to the stanchions which was a little too deep to stone out. The only place I could find replacement stanchions was Wemoto. (NOTE: fork bushes are now a discontinued item and I have been unable to find any as spares - genuine or aftermarket).

The old fairing was beyond repair so I ordered a new one from Skidmarx. The quality and fit was very good and only required minimal file work at a couple of mounting locations. I’ve always liked the Lucky Strike and AM-PM endurance racer liveries and in the end decided I would go with the Suzuka winning Lucky Strike scheme. I took the panels, seat, mudguard and fairing with photos I'd collected off the net to Dream Machine in Nottingham. Rather than an exact copy I wanted it follow the theme without it being too cluttered with sponsor logos. After some discussion we agreed on a general scheme leaving them with some artistic license.

The panels had some cracks and minor damage but I was assured that these were an easy repair. I opted for home delivery and the finished items were delivered by Dream Machines own delivery van, each individually covered in bubble wrap. A quick dress rehearsal revealed that the colours were well matched and I couldn't detect the repairs. Overall the quality of the work was exceptional.

It was this point the project was put on hold indefinitely due to various commitments including relocating to another area. I had to stay in a hotel for a while and after moving into my new home I had to wait for some building work to be completed. I didn't have anywhere to store it and fortunately I found Transbike who collected the bike and put it into storage. It would be difficult to find anyone more helpful than Arran who arrived to collect my bike in an impressively modified van. The bike was fastened down using fittings designed and produced by Arran himself, in a very secure manner with no risk of any damage or scuffing occurring and taken away. When I was ready I called Arran and it was returned in exactly the same condition it left in.

The bike was now taking shape but it was difficult to start and would splutter and die after a short warming up period. It seemed like fuel starvation and I checked the vacuum pipe for kinks and that I'd connected it correctly but I couldn't find anything wrong. Next I checked the tap internals and replaced the rubber diaphragm with a new one but it was no different.

I found a gravity feed modification kit from Bellway Engineering on eBay (again!). Theres another slightly different version for NC30 and NC35 models. Initially I didn’t want to go down this route and a gravity feed mod using standard parts is well documented but I thought I would give it a try as it looked a neat and simple kit. It was delivered in lightning fast time, installation took no time at all - take off the tank, remove 4 phillips screws, aluminium plates with spring and rubber diaphragm from the tap and replace with new cover plate and allen screws. I inserted a bolt (supplied) into the vacuum pipe which I tie wrapped to the frame as this is now redundant. It fired up third attempt, sounded a little rough at first and then ran smoothly after all the rubbish had burnt off. It now starts immediately and cleanly first time, every time. I still don’t know what the problem was before as the tap internals were new and correctly assembled, I can only think that insufficient vacuum was being generated due to a blocked hose connector.

Fuel gravity feed mod for NC24

The next job was to fit the Datatag kit I'd bought at the NEC Motorcycle Show. Discounted and a beanie thrown in – a bargain. Easy to fit, the only drama was when I dropped and almost lost one of the two glass transponders supplied when I stabbed myself with the very sharp insertion tool despite the warnings on the packaging!

The standard 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 and I also found this guide intended for VTR1000F which was helpful. I was initially looking out for a connector off an old R6 wiring loom but found a new connector plug kit for £3. Its very important to solder the connectors rather than crimping them on. The regulator was a tight fit and I had to file two rounded slots in the fins to make room for the ht leads which are routed below it.

Yamaha regulator rectifier

Yamaha R6 regulator - 5 pin and not the 6 pin version.

The bike sailed through its MOT but I got an advisory note that there was a noise from the front forks which I'd noticed as I rode it to the garage, a sort of dull clunk. Despite the noise the bike handled fine. There was no play in the forks or headstock and I started to doubt myself and was unsure whether I'd assembled the forks correctly. So it was back on to the Abba stand and the forks were stripped only to confirm that they were in fact ok. I'd noticed during the rebuild that the polymer bush on the anti dive mechanism had worn but had been 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. Searching online I found and bought 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. However I had to open the bush out slightly to accommodate the piston collar which was slightly oversize due to the cracks. Fitting the bronze bush has stopped the noise but I'm looking into using an engineering plastic as an alternative in case there are problems with the bronze. The piston collars are an easy job for a machinist to copy although they will need heat treating. 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.

NC24 Fork assembly confusion - fork servicing can be tricky if both legs are dismantled and the parts mixed or if they have been previously reassembled incorrectly. Some internals of each leg are different and unfortunately there isn't (to my knowledge) an English manual as the NC24 is a Japanese import. However they are very easy to work on and 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 and I've shown them in the photo below. 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 manuals but many people 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.

NC24 anti dive component
The cracks in the collar can be clearly seen in this photo. It seems that when the bush wears and becomes oval the piston collar twists within the bush under load and cracks - the wall thickness of the collar is 0.95mm thick. I have two sets of forks and both were like this and I wouldn't be surprised if the anti dive units of most NC24s are similarly affected.

Original worn plastic bush in NC24 anti-dive piston

With the collar removed the wear in the plastic bush is obvious.

NC24 anti dive piston with replacement bush

Replacement bronze bush in anti-dive piston

NC24 fork leg components

Lower fork leg components

Oil lock piece on fork damper NC24

Correct orientation of the alloy oil lock piece, leaf spring washers and damper rod

Oil lock piece on damper rod NC24

Oil lock piece and leaf spring washers in place on the damper rod

The completed bike

VFR400 NC24
VFR400 NC24
NC24 Speedo
NC24 headlight cowl detail
NC24 front wheel
NC24 rear hub
NC24 front brake caliper
NC24 hydraulic clutch conversion