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3. Let's get started

Just four bolts secure the engine to the subframe so it's quite quick and easy to remove it - even when it's all fitted in the car. Here's the bare subframe with every component removed. It's quite light but the Honda engine is probably less than half the weight of the Mini so it could probably be lightened even more.

Drum brakes will certainly be adequate for this little car. Disc and caliper kits are available but there's not much point. I think the top and bottom ball joints may be new but everything else is tatty and tired.

So, we have a CX500 engine - serial number CX500E - 2311650 which, from online data is from a bike made in 1981.

The front of the engine is looking a bit scabby ........

..... and so is the back. It's been leaning backwards on the lift/bench for a few days and has developed an oil leak from underneath somewhere - could be just a loose oil drain screw. You can see the gear change push-pull cable mod at the bottom of the picture.

Here's the oil leak culprit. I'm not sure if this is meant to be an oil drain plug because it's only an M6 threaded hole in a groove in the casting that goes through to the bottom of the crankcase. Whatever - it worked for draining all the oil out. I ground and filed away the sides of the grooved section and replaced the dodgy countersunk drain screw with an M6 Hex and Dowty washer.

OK - blasting time. I plan to strip the engine - maybe not completely but certainly to check the heads and rings at least and replace the clutch and waterpump seals. But I'll be happier if I clean it all up before I start. I've removed the starter motor, water pipes and everything that unbolts easily. Now it's time to mask and plug all the holes and shafts. Below, I've made soft PTFE plugs for the exhaust ports and clamped them with a steel bar across the manifold bolts.

I cut a couple of plates from 3mm aluminium to cover the inlets. They'll seal adequately with a light smear of silicone.

Gaffer tape around the output driveshaft and seal.

Tapered nylon plugs for the water pipe and starter motor holes.

.... and tapered wooden dowels hammered into the rocker covers. The spark plugs are still fitted but I'd rather keep the cavity clean rather than clear our blasting grit later.

Into our big blasting cabinet then. Some areas of paint and corrosion cleanup quite quickly but areas with thicker paint take a a bit more blasting. I use glass beads and low pressure on aluminium to minimise removal of the metal itself so it's a long job.

It's quite a struggle to reach all round a complete engine of this size in our blasting cabinet. I rotated and flipped it in every possible direction. A new glass window in the cabinet, additional lighting and a quick check through the opened door every now and again helped find every untouched area.
Not bad after an arm-aching three or four hours in the cabinet. I didn't bother too much with the rocker covers because they're coming off and I can blast them separately.

....and a few other little areas that I missed. Incidentally I take pretty much all of these piccys on my iphone 7 and I must have omitted to switch on the flash for the front shot above. I've used Photoshop to get it close to the natural colour of the rear shot below. 
Right - let's take it apart.

I actually removed the starter motor before blasting the engine. There's some corrosion on the case but it made a worrying grinding noise when I turned it by hand.

......and maybe this is why. The brushed don't look exceedingly worn but it needs new ones and a clean up.

Here's the coolant pipes and stat housing. It's clearly had neat water as a coolant.

Corrosion isn't too bad though. The worst of it is in the long steel coolant transfer pipe. Of course, the engine has been hanging around, drained of coolant for several years so it's difficult to tell how much of that corrosion is down to dampness inside the drained engine.

This mixed batch of steel and aluminium parts has just come out of the blaster. The steel parts have to be immediately moved to a warm dry environment. Surface rust will appear very quickly on freshly blasted ferrous metal in damp conditions. Blasting has certainly removed visible corrosion inside the long coolant transfer pipe - but you can't see round the bends......

...... unless you use our CBS Borescope (part number #BORE). This has a camera and light on the end of a long, flexible probe. Ideal for inspecting hidden places. Blasting through the tube has removed all the loose, flaky rust so I'll just pour a small bottle of 'Rust Remover' fluid in the tube, plug both ends and swill it around for a while. It's quite thick wall tube and the rust has not eaten into it too deeply so I reckon it'll be OK to use again. I'll be using CBS 'Evans Power Cool' in the engine so future corrosion won't be a problem.

Although our workshops are fairly well insulated - as workshops go, they can still get a little damp and draughty in the depths of an English winter - and my old bones are feeling it more and more. We've tried just about everything over the years with varying levels of success - Electric, Calor gas, Diesel, even a stinky Swiss Army tent heater. However, we recently discovered these little beauties. Problem solved. They will run for a couple of days on five litres of Kerosene or Paraffin and shove-out enough heat for shirt-sleeves attire on the coldest of days. Clean, simple, compact and inexpensive to run. A bargain at around £200 and an absolute necessity for successful painting of our bits and pieces.

Here's what I'm using for the engine parts. POR15 paints are not the cheapest you can buy but they are, by far the best. They cure like an isocyanate - by absorbing moisture from the atmosphere to give an extremely tough and durable finish. All available from CBS, of course.

This handy little paint booth folds up to about the size of a large shoe box. Open it up and you have a turntable, extractor fan and filter. We've ducted the 4" outlet straight through the workshop wall but you can recycle filtered air as shown below. For painting small parts it works brilliantly.

The CBS Airbrush (part number #AIRBR) is easily up to the job. POR15 paints can be hand-brushed or, with just 5% solvent thinners, they can be sprayed. It's important to have a warm environment and important to get the proportion of thinners just right when mixing your paint. Too little thinners and the finish will be rough and patchy. Too much thinners and the paint will run and leave an uneven finish. Experiment on a test piece first.

First, a couple of coats of Grey POR15 Rust Preventative. It's a good first coat, not only for steel parts but it also works fine on aluminium.

Then two or three coats of POR15 Aluminium Engine Enamel.

The engine and subframe have been stored in our workshops for several years and in the previous owner's shed before that - hence surface corrosion on most of the steel and aluminium components. The main throttle butterflies move freely but the rest of the throttle linkage is siezed.

There are cobwebs and mild corrosion but, surprisingly, almost all of the screws appear untouched and undamaged indicating that it hasn't been 'Roy-Rogered' over it's thirty five year life.

A large ice cream carton, a splash of Gun-Wash thinners, a Brass wire brush (available from CBS #BRUSHPAK) and a blast with an airline will remove all the rust and corrosion and bring the carbs back to an acceptable condition. I changed the thinners a few times as the carbs got cleaner and cleaner.
Reconditioning kits are available for the carbs at about £17 each. That's most of the jets, needle, float valve, 'O' rings and rubber gasket.
Most of the fixings on this engine are standard Metric but all are mild steel and corroded. I'm replacing them all as I go along with stainless from the CBS range.
This is what I saw when I removed the air cut-off valve cover - grime and corrosion. I don't think this had ever been removed before so I'm surprised that it's all this grubby.

One of the diaphragms had a pin hole which would obviously affect performance. Well, I guess that's fair enough on an engine that's almost thirty five years old. Twenty eight quid for a replacement pair !!!

This small brass brush is great for cleaning threads.

.... and this 20mm diameter wire disc brush in my Dremel works brilliantly at removing corrosion from grooves and corners..

As you can see in a previous piccy, the steel brackets and plates that hold the carbs together are badly corroded. Blasting it all off is no problem but, rather than painting them, I fancy re-plating them as original. There may well be more steel items either on this project or others that deserve a new Zinc plate so I invested in this £110 Zinc Plating Kit. I can't find any local plating companies nearby prepared to do a small batch and mail order is a bit risky so I reckon it's worth a try.
There's a ton of information online and a few YouTube videos of folk using their home plating kits. To be honest is a bit of a palarva and takes a while to mix the chemicals, sort out the power supply and set it all up. Most of the Youtube demonstrations are of small parts like nuts and bolts which, I reckon, are far easier to plate than the long plates and oddly shaped steel pressings from my twin carb mountings. But her they are, hanging in the electrolyte with the Zinc anodes connected together and a fish tank heater to warm it all up. There is an aerator (fish tank pump) that pumps air to the bottom of the tub to agitate the electrolyte for a more even coating.

Here's the device that regulates the plating current that passes through the electrolyte. 
I added my own ammeter to get a better idea of the best combination of time and current but it's all a bit unpredictable with components like mine. I stripped off the plating in acid a couple of times and started again before I worked out an acceptable modus operandi.

The end result is acceptable.

POR15 Aluminium Top Coat Aerosol is a new product for CBS so I tried it on a couple of small parts like this coil mounting bracket. I blasted the parts and sprayed the paint 'direct to metal'. Seems great, so far.

My Vincent Comet engine was an awkward shape so I made a steel cradle for working on it on the bench. However, the Honda CX500 has a totally flat bottom that I thought would sit nicely on a 15" round turntable, making it much easier to spin it around. So, I bought this 14", aluminium 'Lazy Susan' bearing on ebay for about fifteen quid. It's amazingly good quality and will easily take the weight of the CX. I cut a 15" disc of MDF, gave it a quick coat of lacquer and screwed it to the bearing.

Engine on turntable.

Here's the water pump internals.

There's not much apparent sediment or corrosion in the housing ....
.... but the cast iron impeller has some surface rust and the ceramic bearing looks like it can't be trusted.
Removing the inner ceramic bearing and oil seal was a challenge.

Here's the blasted impeller and half of the new ceramic bearing.

I like to use a tap to clean out all the female threads to remove corrosion and any old thread-lock. I dip the tap in vaseline.......
.... which traps the debris in the flutes of the tap. Wash it off in thinners between each tread. It doesn't hurt to give each thread a blast with an airline.
Time to take the clutch apart but it needs a special 4 tooth socket to undo the main centre nut. I made one from an old socket.

Here's how I made it. I used a 1mm thick steel cutting disc in my Makita angle grinder to make vertical and horizontal cuts in the socket, dressing the remaining pegs until they are a good fit on the nut.

Time to plop some paint on the engine. It's been a while since I blasted it but it's been sitting on the bench in a dry workshop inside a big plastic bag so it's still in perfect condition for some POR15 Etch Primer. It would be pretty much impossible and very messy to reach every cranny with an airbrush so I sprayed the aerosol into a cut-off milk carton (thoroughly washed out, of course) and brushed it on with a top quality 1/2" brush.

The following evening it was the turn of POR15 Aluminium Engine Enamel.

Seemed like a good idea to change the 36 year-old driveshaft oil seal.....
...... and the gear selector shaft oil seal and here, the front camshaft oil seal. This end of the shaft drives the Tacho and Cooling Fan. Neither of which will be used on this car.

You'll see in earlier piccys that the die-cast Rocker Covers were equally as scabby as the rest of the engine but I reckoned they deserved to be polished. I soaked them in Gun Wash for an hour to soften the old paint then bead-blasted them. Here I'm dressing the casting with an unusual., abrasive flap wheel that I discovered on the stand next to us at the last NEC show. This one is 600 Grit but I also have 240 and 400. They work pretty well removing casting marks and prepping the surface for polishing.

I thought I'd do a final check on the engine by rotating it in 5th gear with mole grips on the drive shaft output and gear selector (protected with strips of aluminium, of course). I took a peek down the plug holes with our 'Borescope' and checked the valve gear was working as it should.
The coils were originally mounted to the bike frame but I mounted them in about the same relative position on top of the engine.

The water pipes are all fitted and a 'highest point' take-off has been welded to the top of the thermostat housing. This will go to a header tank. 
It won't see any oil, water or fuel until it's ready to fire-up in the car but I'm confident that it'll be a solid, reliable engine. And that's about it for now. Time to get on with the body.

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