This latest bike was added to my collection after I remembered my friends and I discovering (back in the 70s/80s) the disproportionate amount of fun that we could have with these little bikes. In those days, I had several Dax’s and a Chaly; all now long passed on from me, but happily, apparently still alive according to the UK DVLA vehicle database.
It was clear from the Internet that there was now an enormous worldwide following for these small Honda-based ‘fun bikes’, especially with the availability of ‘cloned’ Chinese models and wonderful after-market parts at bargain prices.
I then found a genuine Honda 1979 Z50JZ that, despite several reductions, had failed to sell on eBay before the owner had emigrated to New Zealand, leaving the bike in the UK with his friends.
Luckily, I was still able to do a deal via email and I collected the bike in December 2010. Although it had some useful modifications, it clearly still needed a lot doing to it, so within hours of getting it home, it was reduced to a pile of grubby components.
I knew from bitter experience that under-powered bikes were a nightmare on busy UK roads, so first on the shopping list was a decent engine. After much searching for other buyers’ opinions on forums across the globe, I decided to install a new YX140 with a Z40 cam, as used in Stomps and other similar pit-bikes. The engine was claimed to put out a healthy 12-14hp and had a good reputation for reliability, so it seemed like a good investment.
It was important that the finished bike appeared reasonably standard, rather than simply like a pile of shiny goodies lashed together, as I had seen too often online. Therefore, with the new engine positioned in the bare frame, I took my time to offer up and modify the oil cooler before welding on the discrete new bracket that I had fabricated.
I also took the opportunity to acquire and fit a pattern Honda VIN/’rego’ plate…a subject of much discussion on the Australian monkey bike forums! My bike never had one from new, only having the frame number stamped on the headstock. However, despite the very thin paint, this was barely readable even before the headlight etc got in the way, so I thought it was worth making it more accessible.
Before I bought the bike, a previous owner had fitted a very exotic oversize Takegawa swing arm, so all I had to do was polish that up, and I couldn’t resist advertising the revered brand with some genuine stickers; almost impossible to obtain, but finally sourced from France.
The chromed rear shocks looked more stock than the fancy new Ohlins I was tempted by, so they were given a second chance. However, although basically sound, they had considerable surface rusting, so they needed to be completely stripped. After first discovering online that this was actually possible, I then made up my own spring compressor with a couple of scrap gears and two workshop clamps.
This worked far better than I had dared hope, and after some serious polishing, I was able to reassemble the units, both looking like new again.
The bike also came with some decent 10in alloy wheels, but I thought I could improve their looks a bit by spraying the inner sections metallic gold, as I had previously done on my Harley, and various sports cars. Naively, I expected the split rims to be easy to dismantle but sadly, I was wrong!
Time had bonded the tyres to the aluminium and despite blood, sweat and many profanities, I was finally forced to admit defeat and spray the wheels with a tyre still attached to one half. Still, I think it was worth the effort…
The mudguards were chromed plastic and looked fine. However, the thin alloy plate that relocated the rear one to suit the extended swing arm was already fractured, so I re-made that in steel and rubber-mounted the mudguard to reduce vibration. At the forward end, I welded on some spacers to match the original frame tube above. This put the mudguard in the right place relative to the tyre and also reduced the visual impact of the modified swing arm.
As the new engine had been ordered with a 12v lighting stator, I tried to find a suitable battery to fit the original tiny 6v battery holder. Unable to source one, I then investigated the possibility of using a capacitor instead, since I only wanted to stabilise the lighting voltage. Following online advice, I bought a 10,000uF capacitor from Ebay for a few pounds and, despite it being larger than I had anticipated, I just managed to squeeze it under the original side panel.
I also bought an original CRF50 engine casing from the USA to cover the flywheel magneto. Along with some black paint on the alloy barrel, the whole engine was looking more ‘Honda-like’ by the day! Even the angled after-market red K&N-type air filter fitted perfectly and looked remarkably standard.
The petrol tank initially appeared sound, but had a slight dent in one side and considerable internal rusting. Stumbling across methods online to de-rust tanks using electrolysis, I thought I’d give it a go. Although it took weeks rather than the days suggested, I was very pleased with the end result, especially as a local garage did a great dent repair and spray job for only £35.
With the pattern stickers applied, the tank looked brilliant. I was definitely going to have the ‘Z50R-style, red with wings’ paintjob anyway (regarding it as Honda’s best), so it was just fortuitous that it was also exactly right for a 1978-79 street-bike model like this one.
The fuel tap did initially foul the choke knob on the new carb (as I had already feared, after reading the forums) but by removing the lower heat-proof spacer on the inlet manifold, then routing the fuel pipe around the carb body, I was able to solve the problem. It was close, but that just made it look even more original – result!
A previous owner had obviously grafted on a wiring loom from something like a Dax, as under yards of sticky insulating tape, I discovered all the associated warning lights from the larger speedo assembly. As I also wasn’t obliged to have turn signals anyway, I took the opportunity to strip the wiring back to the basics, removing about two thirds of the unsightly mess I had originally started off with.
In the past, the forks had also been replaced (along with the added disc brake) from a Chinese clone bike, maybe a Skyteam. They had also been extended 50mm with alloy slugs; a practice I recall from my past as being seriously frowned upon, but which now seemed to be acceptable on these small bikes. However, I took the precaution of replacing the rusty retaining bolts with stainless ones made to order and changed the perished brake hose for a braided one from a scooter.
The fork sliders were sprayed silver and the rusty chrome top yoke was sprayed matt black, to look more like original Honda components. The Daytona quick-throttle assembly was already on there, so I left that alone, along with the chromed bar weights that also protected the hand-grips.
I then found that the knobs that secured the original folding handlebars had seized solid over the years. Just as I was getting resigned to leaving them like that, my efforts with copious ‘Plus Gas’ releasing fluid and a big strap wrench paid off, and suddenly they were free! Needless to say, they got well-greased before being reassembled.
The exhaust appeared to be a Daytona Spitfire twin-outlet type, of good quality. However, the mounting bracket had obviously previously failed and been dreadfully re-welded, so that was now re-done properly, using the new engine as a jig to hold the pipe in the right place.
Unfortunately, the chromed heat shield was stamped ‘Jincheng’, but I was able to fold that inner edge over so it wasn’t visible, and an OEM-style warning sticker completed that ‘stock’ look.
Finally, the genuine Honda seat was on the bike when I got it, having been recently fitted by the previous owner. It was certainly very comfortable, but I would have preferred it in black.
(However, with this new ‘mega-engine’ now fitted, perhaps it was just as well the bike has got a brown seat…!)
Now it was time to see if the beast would actually run…..
Starting it up, and that first trip out…
Well, sadly it wasn’t exactly a first-kick start, which would have been nice, if a trifle over-optimistic. The big surprise was the amount of compression encountered! Although not as bad as the Yamaha XT500C that I had bought brand new back in 1977, there was clearly not going to be any repeated ‘lashing away at the kickstart’, as one often witnesses happening with small bikes. It also meant rapidly finding out why the engine wouldn’t start, before I became totally exhausted.
The spark was the best I’d ever seen, so obviously no problem with my reworked wiring, which was a great relief. The petrol was fresh and seemed to be getting to the plug, so I kicked the engine over once more, this time with a handful of throttle. That did the trick and away it went, sounding really beautiful! I was amazed at how easily it revved too, despite the original flywheel; I could only imagine what the lighter ‘inner rotor’ option must be like!
The engine sounded reassuringly quiet mechanically, and tightening the banjo bolts on the oil cooler soon stopped the slight leaks coming from them. As expected, there were a few whiffs of smoke and the smell of hot new metal as the engine began to warm up for the first time, but otherwise, everything seemed fine.
Luckily, since the bike I had originally bought was already MOT’d and taxed, it was now time to get out on the open road….and as if to encourage me, the sun even came out!
Thankfully, everything went very well, as the bike started without any problem (or choke!) and soon settled down to an even tickover. I had already set the clutch adjustment and this proved to be fine too; the gears engaged easily and pulling away smoothly was easy.
Although I was very aware that I mustn’t stress the new engine, there was obviously plenty of power there, even at low revs. It was a bit strange getting used to the ‘4-up’ gearshift pattern, as I was accustomed to simply shifting down whenever I stopped, but doing this now this just left me trying to move off again in neutral! Still, I’m sure that will become instinctive with a few more miles practice; after all, I used to swap seamlessly between Brit right-hand and Jap left-hand gear levers with no problems…well, most of the time, anyway!
I was also relieved to discover that the final gearing ratio seemed to be perfect too. On the advice gleaned from reading similar enquiries on various forums, I had opted for a 17-tooth sprocket on the front (the biggest that would fit under the cover) with a 28-tooth on the wheel, driven with the heavier duty 428 chain. Although I cannot establish top end speed until the engine is run in, this ratio seems to work well with the currently available power.
For my first trip out, there was one really obvious location – Monkey World! This is the largest primate rehabilitation facility in the world and it is located only a few miles from my home in Dorset, on the south coast of the United Kingdom. It is a very worthy charitable cause and also has an impressive collection on ‘monkey-related’ products in its online gift shop; there’s a link to the home page here:
http://www.monkeyworld.org/home.php
Of course, I simply had to get a photo of myself with the sign outside!
Only about a mile down the road, there is another notable location that has a motorcycling link, albeit a rather tragic one. It was the spot where T.E. Lawrence (AKA Lawrence of Arabia) crashed his 1000cc Brough Superior and was killed in May 1936. Although there have been countless conspiracy theories surrounding this crash (as with Princess Diana), it seems more likely that it was a simple accident, caused by Lawrence swerving to avoid two boys on pushbikes. However, the memorial stone subsequently erected now provided another ‘photo opportunity’ to record my little monkey’s successful ‘maiden voyage’!
After many more miles of pottering round quiet back roads amidst the beautiful Dorset countryside, then on down to the beach, everything on the bike was still working well, so it was with a mixture of pride, elation and relief that I finally headed for home.
Here’s to many more trips over the years ahead….!
PS: Although it took me a while to finally get the bike, my interest in monkeys started a very long time ago…
Here’s me with my first pair, circa. 1965!
oldjapbikeguyUK 