Jerry Thurston recommissions a Honda Cub!
So, this feature is all about the most common motorcycle of all time, one of the 87 million Honda cubs built between 1958 and today (well, 2014 according to Wikipedia!). This Honda Cub is a 1969 50cc variant that had genuinely been in a barn for years and although it is primarily to be used as paddock transport at historic race meetings as it will be on the road at some point the work has been done to MOT standard. If you’ve been lucky enough to find a motorcycle that’s been in the proverbial (or real) barn for decades it always looks like it could be up and running without too much difficulty. But rather than just sloshing some fuel in and giving it a kick let’s look at what’s involved in a careful recommissioning of something that’s been standing for ages. Here’s how I did it and what it cost! The first job is always simple: give the whole machine a good clean and degrease. It is going to be far easier to see what you are doing and when you remove components you won’t have muck getting into the motor. I always drain the old oil overnight and if the machine has any sort of oil pan, pull this off – there is often a considerable layer of muck sitting in the bottom ready to be sucked up by the oil pump! Then fresh oil and replace any filters before you kick it over. The Honda has no filter, relying instead on a centrifugal filtration system fed via a gauze strainer. What Honda recommend is draining the old oil, removing the right-hand side cover and cleaning the gauze (the gasket is £9.50). Given that it holds a scant 0.7 of a litre (2L semi synthetic 10/40 £10) I went further and once it was running changed the oil twice in quick succession, but I’m slightly ahead here, we need to get a spark first! I needed to connect a good battery: this one is 6V but later Cubs are 12V. I managed to get a good quality 6V 4 amp battery for £18, not forgetting to put the negative to the blue wire, positive via an 8 amp fuse to the red. Beware though, If you find a ‘faded’ red wire and connector, ignore it, it’s not faded it’s meant to be pink and it’s a spare. The positive needs to go to the bright red double connector that comes from the flasher unit. I always do a quick test for power when the ignition switch is switched on by press the rear brake lever or trying the horn, if you get light or a peep, it’s all good to go. To check for a spark, I push a spark-plug into the cap and rest it on the cylinder head, ignition on and kick. OID school: but I find I have no spark, so it’s time to change the plug and check again. Still nothing so I need to go deeper. The Ignition/ generator system on these earlier machines is pretty robust, so I figure that a simple clean of the points through the flywheel might work. I’m still getting nothing so it’s flywheel off to investigate further; the correct left-hand thread 27mm puller is about £8 so it’s not worth risking damage using anything else.
With the points out a simple continuity test proved that they didn’t pass current but a really careful clean with the blade of a knife sorted this out (genuine replacements cost £16). If the points are good and there is still no spark, you can check the condenser, set a multi-meter to ohms, place the positive terminal on the centre connectors the other to the body and hold for a few seconds, this should charge the condenser slightly, change to the volts setting and do the same again and if it’s good you’ll see the reading fall as it discharges, (by the way, a genuine condenser is £16). At this point I had spark but if you are struggling, check all the wires, looking for dirty connectors or a break somewhere paying particular attention to any pinch points. Even if you have a spark it’s worth doing this, I found two trapped and damaged wires in the rest of the loom which needed attention. With a spark I was now on my way, but it’s not time to try a start yet. I decided to check the fuel system first. Top tip, the fuel tap is on the carb not the tank on these early Cubs so have a container ready for when you pull the lines off! Once the tank is empty look into the fuel tank with a torch; hopefully it’ll be clean and bright, but any flakes of rust are going to clog things up. A handful of small nuts and bolts carefully rattled around will scurf most of the rust debris, followed by a degrease then tank rust remover. Beware though, as this will search out any pin holes especially in the seams. If you decide that you are merely going to live with it, a £2 disposable fuel filter in the line/s (the Cub has two, one main the other reserve) will save much angst later. A thorough clean of the remaining fuel system is always prudent and I replaced any hardened or rotted lines and I also gave the carb and the jets a once over with carburettor cleaning fluid and compressed air. Time to give the cables and controls some attention too! The Honda’s throttle was sticky, which I figured was dangerous even on a 50! The twist-grip was stripped and re-greased and the cables were checked for damage and when passed fit it was re-lubricated. The difference this made to the controls was a revelation and it’s always worth doing on a recommission. I don’t trust brakes until I have checked the shoes, but be cautious, old brakes may
still contain asbestos linings, never blow them out with compressed air. I tackle unknown brakes while wearing an air-fed mask and even then I squirt lots of penetrating oil into them while they are still on the bike to damp them down, then remove and wash everything in old two-stroke oil which doesn’t dry out. Only when they are surgically clean do I use brake cleaner to remove the oil residue. I suppose I should say that this is what I do, not a recommendation of any safe technique! Mine on the Cub had a complete strip-down, copper grease on the pivots and new shoes (genuine, £10 for all!). While I was there, I realised that the cush drive rubbers often suffer over time and mileage, so I checked and mine were shot but were easy to replace while the wheels are out to check the brakes and a genuine set came in from ebay at just £18.85. I had the wheels out so I checked the spokes. As a minimum, I check for any broken or loose spokes and give the wheel a spin to check that it is reasonably true. Both of mine were, which was a relief as I would have had to budget for a wheelrebuild otherwise! Decades-old tyres and tubes will undoubtedly be past their best, so I replaced them. I bought Michelin Street Pilot, one size up at 2.50 x 17 for £37 pair and the tubes were £15 pair. The exhaust is where I went to town. On any old four-stroke this is likely to be rotten, a pattern replacement is £36 but because this machine is going to be used as paddock transport I took the opportunity to fit the only nonstandard part on the machine: a stainless steel Kepspeed race pipe which was a ‘whopping’ £89.95! With the ’69 Cub MOT ready I had a total recommissioning bill of £297.02, although this did include a few extras that weren’t strictly necessary, such as a new seat cover (£35) and footrest rubbers (£10 pair), the chain was marginal so was replaced too, without these and the exhaust upgrade my costs would have been £109 less, but I’m happy! cmm
She certainly needed a good recommission!
Jerry went through the bike methodically.
ABOVE: She’s going to be used, so it’s not a nut and bolt resto.
BELOW: Work was needed on the mini-motor.
Cleaner, safer and better than before: if not immaculate.
Normally an area for rot!
Forks and spokes need to be A-OK.
Yeah, best replace that.