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 Little Dream 07 - 'the Corporal'

Part 4

The Rebuild Starts

So, with the suspension in place front and back, I had a rolling chassis..... time to stuff a motor in it to make it a motor-bike again!

1986 Honda CB125TD-C - Renovation

Starting to look more bike-like, isn't it? And getting it to this point was a pretty big mile-stone, to help keep my spirits and enthusiasm going. But took a lot more time effort and work that its state of completion suggests! But it finally looked like something you could ride, so I took a photo. Shame its a blurry one, but still.

1986 Honda CB125TD-C - Renovation

Getting into the 'meat' of the project here, but a lot of stuff was being done 'here and there'. I mean, stripped most of the old girl down during the initial investigations, and haven't shown you any of the bits I took off the frame to sort the steering and suspension, or what happened to them between then and starting to put stuff back together.

Engine

So starting with the engine. It had been checked over, right at the beginning, so there was little reason to open it up, but it didn't look very pretty, and needed a little bit of make-up. Paint Stripper is the best way to get into all the detail of the castings and fining, but a wire brush the best way to actually get the stuff off! So it was a case of paint a bit, brush a bit, wash. Let dry, then repeat, doing it in little bits between doing other stuff. Then add paint.

1986 Honda CB125TD-C - Renovation 1986 Honda CB125TD-C - Renovation 1986 Honda CB125TD-C - Renovation

1986 Honda CB125TD-C - Renovation 1986 Honda CB125TD-C - Renovation

This IS only a 'blow-over', the whole engine painted as a 'lump', the critical bits masked off, rather than the individual piece parts individually painted. But, without doing a complete tear-down to bare castings, this is often the best way to paint the engine. Take any cases off to paint separately, and you risk getting paint inside the engine, and potentially blocking oil-galleries and things

Engine paint is a frequent question on the forums, and people suggest all sorts of things; Hamerite barbeque paint; Halfords wheel-silver, high-temperature exhaust paint, and all sorts of stuff in between! High-Temperature brake calliper paint is a common one.

Anyway, the important thing is that high-temperature paint, normally needs to be 'cured' at a high temperature, often the operating temperature of what's painted. Until it's 'baked', it remains slightly soft and can flake.

If you choose the wrong paint, its possible it may never cure. Most common example is the Very-High-Temperature (VHT) paint sold for painting exhausts. Exhausts get very, very hot, especially the headers near the cylinder head, but the cylinder head itself often wont get anywhere near as warm, so painting the actual engine with VHT, quite likely it'll never get hot enough to cure properly, and will flake off, or stay soft.

And its actually only the 'business-end', the cylinder head and barrel of an engine that gets all that hot. The bottom end can run quite cool, and in many cases is actually designed to. On an air-cooled engine, you do need a high-temperature paint, because the business end does get hot, but on a water-cooled engine, with a water-jacket stabilising the temperature at around 88DegreesC, its often not actually THAT critical, though 'cosmetic' panel paint might not stand the occasionally localised hot-spots and generally warmer temperatures. When I rebuilt the Rover V8 for Bert, I used lots of different paints for the different parts, but the engine block was painted in silver wheel paint!

For the Corporal, though, I used PJ1 Engine Black. I cant remember the exact temperature range its designed for, but it says on the can 'For Air-Cooled Engines'! so I reckon that's about right! But it does stay soft until the engine is run up to temperature, and its worth noting it gives off some smelly vapours as it cures, so make sure your in a well ventilated area before you start it for the first time after painting!

Wheels

The wheels on the CB125TD-C 'Super-Dream' are the second generation 'Comstar' construction. Their the same construction as the first generation, which is to say that they have a hub, and a rim, like a conventional 'wire laced' or spoked wheel, but instead of wire spokes, they have flat metal plates bolted between them. Honda were very enthusiastic about them in their day, vaunting how much stronger and lighter they were than wire-spoke wheels, but more forgiving and durable than cast wheels. (In the early days, cast wheels had a reputation for stress cracking)

1986 Honda CB125TD-C - Renovation

They are, now, a right royal pain in the proverbial. The plates are riveted to the rim, and bolted to the hub, with anti-tamper bolts, and there's a message stamped into each plate that says 'Do Not disassemble'. The plates and rim are also anodised aluminium, while the hub is painted. So cleaning them up is awkward. Be a LOT easier to polish the spoke-plates if you could take them apart, and clean and re-paint the hub. But you cant! and its really bloomin' awkward to get between those plates to clean them! However, they were cleaned up, as best as, and the fittings that go on them were re-painted.

Now, I've mentioned it before: "The important stuff is having good tyres, steering, brakes and suspension, so that when the motor has got you moving, you can move in the direction you want, and stop when you need to!"

Tyres on these wheels didn't inspire me. But then they didn't make me cringe either. They were obviously a bit old, but they weren't worn out, squared or perished. As tyres go, they were 'adequate'. {See Comments later in Blog. When Presented for MOT 22/03/11, it passed with flying colours gaining only one 'advisory', commenting on the tyres exactly as I had on initial inspection} A nice new pair of Mitchelin Pilots, would probably do wonders for the bike, but they are about 100 a pair, more than twice the price of a pair of 'commuter' tyres of the sort this kind of bike would normally get, and the ones on it were probably better than they would be, so I left them there, 'For now'.

{Note: Recommended Tyre Sizes are 'Tubed', 3.00-18 Front, 3.25-18 Rear. These are old 'Imperial' tyre sizes. Checking the metric conversion charts, 3.00-18 converts to a 90/90-18, and a 3.25-18 converts to a 100/90-18. Now, most modern tyres are Tubeless, and normally mount on a different rim profile, and often cant be fitted with tubes. Though in sizes common on older bikes, sometimes 'compatible' tyres are marked 'can be fitted with tubes'. They tend, though to be a LOT harder to fit, and often can only be put on with a professional tyre fitting table. However, it does rather broaden the possible tyre choice. HOWEVER, converting BACK from the metric sizes, there is overlap with the Imperial sizes, and the 90/90-18 is also an equivalent for a 2.75-18, and the 100/90 an equivalent for the 3.00-18. This is rather 'convenient'. Those are the front & rear tyre sizes of the 'earlier' Twin shock CB125, but better still, they are a MUCH more common 'lightweight' sizing, used on bikes like the YBR125 or CG125. And its those sizing we chose to Donna's 'Pup', when getting her a nice pair of Mitchelin M45's. The tyres ARE slightly smaller in width, and consequently in rolling diameter.... its quarter of an inch, barely 6mm. And the advantages far outweigh the disadvantages. First of all, cost and availability. There are FAR more tyres available in this sizing, from different makers, so they are easier to find, and tend to be a bit cheaper for similar grades of tyre, whether looking for lower cost or higher grip. Next, more of the bikes that fit those sizes have spoked wheels, hence need tubed type tyres, so they tend to mount better, and more easily, and they are much more DIY fittable, for further savings, and serviceability, should you get a puncture. Effects on performance are negligible. Narrower tyre has some advantage, ultimate dry grip may be slightly sacrificed by the narrower section and smaller contact area, but in the wet, the narrower tyre will dispel water from the contact patch more easily. Meanwhile, the narrower tyre will provide lower rolling resistance, so they are good for economy AND 'speed', as well as making the steering a little lighter and more precise. The reduction in diameter, does lower the gearing though, which will increase engine revs for any given speed, and increase the number of turns the front wheel does to cover a given distance, making the speedometer 'over read' a little. Working it through, though, its 6mm over 600.... ie 1% Its a VERY small difference, though it IS noticeable in the steering and rolling resistance, surprisingly.}

The bearings in the hubs are semi-sealed units, so they cant really be taken apart and greased up or anything, so I checked for obvious play in them, and as they seemed OK, left them alone too! As I did the sprocket, sprocket bolts and cush-drive bushes, which also all checked out OK. So onto the brakes

Brakes

I decided to replace the front brake assembly. It worked 'OK' but the pistons were quite deeply pitted, but not rusty, suggesting it had been overhauled, but re-using the old parts! I was not impressed. The pistons worked, but use, was likely to see the piston seals chewed up, if not immediately, certainly when they were pushed fully in to accommodate a new set of pads in the future. I was also not impressed by the front brake hose. It was a piece of industrial nylon hydraulic line. Hard and not as flexible as rubber, and without any protective sleeving, it was liable to kink when flexed through suspension movement, or be damaged by road debris or snagging.

So I scoured the ready-spares store, also known as 'the heap'. Two complete front brake assemblies immediately presented themselves. The first was the one off LD01, and was reasonably serviceable, but the other we had removed from Donna's bike, 'The-Pup'. There was very little wrong with that one, which was why we hadn't used it on 'The-Pup', choosing instead to completely recondition a completely useless assembly that had been in one of the boxes of 'spares' acquired, to give Donna a chance to learn some mechanics. So I chose to use that one, stripping it down, and cleaning it, masking and painting, greasing and re-assembling.

The rear brake was actually quite good, but again, it was stripped cleaned and greased where needed, piece parts being painted between times. Fitted up it worked very well.

And that takes us up to what you see in the first pic, a rolling chassis, with engine, needing detailing out, but that needs lots and lots and lots of piece parts looking at and sorting out, so the next thing to look at was the plastics.

 

NEXT: Part 5 - Tackling the Plastics

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