I will return the motorcycle to its original light silver color, so the non-standard blue paint had to come off.  For this work I used Aircraft brand paint remover.  This blue paint was rock hard and initially resisted the paint remover, so I had to lightly sand the surfaces to allow the paint remover to do its work.  The paint eventually surrendered and flaked off as expected.  At this point I discovered a few areas with very thin body filler under the paint.  The paint remover also removed the body filler, so I’ll need to fix that before priming the panels.

I also began the process of reassembling the engine.  The alternator rotor needed to come off, which required an M16 1.5 fine thread pitch bolt to be screwed into the rotor.  My local hardware store only stocked M16 2.0 standard thread pitch bolts, so I had to order a single bolt online.  Armed with my special bolt, the alternator rotor easily popped off as I threaded the bolt into the rotor.  This allowed the old crankshaft seal to finally be removed.

I disassembled all the transmission pieces, cleaning each piece with solvent before reassembling them with engine assembly lube.  The engine assembly lube has graphite and molybdenum to aid in lubricating the engine during the initial start-up, before the oil has a chance to circulate the first time.  I was quite pleased with the condition of the transmission gears.  I wasn’t able to find a single tooth that exhibited any visible wear.  The gear “dogs”, which engage the gears when the transmission is shifted, looked like new, without the slightest rounding.  This transmission should shift nicely.

The crankshaft was cleaned and the bearings lubricated before being set into the crankcase.  The camshaft drive chain was installed at this stage.  All engine seals were replaced as I reassembled the engine’s lower end.  I stopped at this point but will pick up next time with the installation of the pistons, cylinder and head.

I used a graphite-moly engine assembly lube during reassembly.  It only took about 10 minutes to reassemble.  This oil pump body also contains the oil drain bolt.  The original drain bolt was previously chewed up by earlier owners that apparently had only a pliers in the tool box.  I replaced this with a new zinc chromate plated magnetic drain plug.

I will soon be reassembling the engine.  I have ordered the M16 1.5 pitch bolt I need to remove the alternator rotor from the crankshaft, after which I can remove the old seal and re-lubricate the bearings before reassembly.

Today I finished rebuilding the carburetors.  It’s a fairly simple process, made easier since the carburetor bodies were cleaned with the vapor honing process I covered in my January 29 post.  The carburetor rebuild kit included parts specific to this model of motorcycle, so reassembling the carburetors was easy work.

The carburetor rebuild kit included new brass jets, springs, gaskets, o-rings, float bowl valves and adjustment screws for both carburetors.  The adjustment screws and throttle jet needles were set to the default setting, which should be fine for starting the engine.  Once the engine warms up and breaks in for at least 50 miles, I’ll go through the process of setting the adjustments to balance the carburetors and fine-tune the settings for a smooth idle.

I have all the engine parts needed to begin reassembly, so stay tuned.

In another example of overkill, these forged aluminum pistons from Wiseco are designed for high-performance applications, but are lighter and stronger than the stock cast aluminum pistons.  The new iron cylinder liners will be installed in the cylinder block after I have it media blasted to clean away decades of oxidation and grime.  The cylinders will then be bored and honed by a machine shop to fit the new pistons.

I’ll be taking the engine block castings, cylinder and head to a media blasting company in January.  I want to be reassembling the engine in February to stay on track.  As always, I’ll post updates when progress is made.

Typical for Honda engines of the period, there is no external oil filter, but instead a centrifugal oil “slinger” which removes particles from the oil by spinning a finned chamber at high speeds, causing the particles to be thrown to the outside of the chamber instead of circulating through the engine.  There was a heavy accumulation of crud in the chamber when I opened it, which required heavy scraping to remove.  I suspect that this chamber wasn’t cleaned with any regularity, if ever.

I have yet to clean all the head parts, but so far I’m pleased with their condition.  The valves look great, as do the valve seats.  At this point I plan to clean and lightly lap the valves into their seats during reassembly.  The valve guides are also in excellent condition.  After taking measurements with a micrometer, the camshafts are all within spec, and at the high end of the range, too.  I already have a new camshaft chain, so I didn’t bother measuring the original.

I’ve removed the iron cylinder sleeves, and will simply retire them.  I’ve ordered new forged pistons and iron cylinder sleeves, which should arrive by the end of the year.  The engines cases, cylinder block and head still need to be cleaned and either bead blasted or vapor blasted to return them to original appearance, after which I’ll have the cylinders machined and honed to fit the new pistons.

These engine rebuilds are lot of fun.  I’ll post updates as progress is made.