BACK TO TO THE ENGINE
With
the cases de-greased, I was able to begin a re-assembly of the bottom
end. I opted to just use some Cast Coat Aluminum spray paint to use
on the bottom cases, cylinder head and the top cover. Getting them
all vapor blasted would have added another $400 to the ever-growing
price tag. I rifled through all of the NOS transmission parts and
managed to put together an upgraded transmission with all back-cut
gears. The crankshaft was carefully reinstalled on the locating pins,
being careful not to dislodge the main bearing pin for the rotor end
of the crankshaft.
Even
after soaking in a hot tank the leftover gaskets were stubbornly
still adhered to the engine cases, requiring an additional 45 minutes
of careful scraping and leveling off of the mating surfaces. When
you come across the old asbestos-based gaskets, you will find them to
be quite challenging to dislodge.
I
used some Moto-Seal, which is equivalent to Honda Bond and tightened
all the fasteners equally. The engine came with the bottom center
front studs having plain washers and nuts vs. the cap nuts and copper
sealing washers. There is a special long 6mm nut that goes together
with the aluminum sealing washer for the bottom case, just below the
oil outlet, however they were installed on the opposite side of the
cases. There were a lot of little assembly errors discovered as I
went along.
Once
the cases were married together, the engine can be flipped over to
add a new camchain guide roller. BTW I installed an endless camchain,
this time, over the crankshaft before assembly. I fed it over the new
guide roller and it awaited being pulled up through the cylinders and
onto the updated camsprocket.
From
1960-62, Honda did NOT use a primary chain tensioner system for all
of their 250-305 engines. I had to sift through my stash of parts to
find a good shift shaft, which has to be installed before the primary
chain and sprockets are fitted up. I was using a later rubber-cush
drive clutch outer, but when I pushed it fully onto the main shaft,
it started to bind up the shaft and clutch hub. I had to swap it out
for another good used part as there was some kind of machining flaw
with the other one.
I
ditched the big 6 plate clutch pack, which has no retainer wire
grooved fitted to the clutch hub. I have been upgrading the clutches
to the later 1966-67 CB/CL77 clutch assemblies with a two groove
inner hub to hold the 3mm Plate A and then a set of friction and
steel plates in the next groove. I used some similar sized fiber
plates, which are probably from a CB350 with lots of radial grooves
and are only slightly thinner than the 268-020 OEM plates. The outer
pressure plate has four angled holes to help evacuate the oil trapped
inside the clutch assembly, which eases the tendency to slip.
I
had a NOS clutch cover and oil pump cover for the left side, so
replaced the old originals that were scuffed up and worn. All new oil
seals were installed in the engine along with a NOS neutral switch.
The oil filter received a good cleaning and new o-ring. It had about
a 1/16th inch of crud built up inside the filter rotor. The clutch
cover has the early small hole design, so you must remove the whole
clutch cover to clean the filter rotor.
TOP
END TIME
I
thought I was all set with the newly-discovered .75 piston rings, but
as I was installing them back on the cleaned pistons, I discovered
that the top ring was actually a STD ring, instead of .75. I recalled
seeing some various pistons in a spares box and luckily there were
two .75 pistons with new rings installed. I transferred the top ring
of one onto the 1961 pistons and then replaced the piston pins with
NOS items that came from the NOS parts stash. I had difficulty
getting the cylinders down over the piston rings on the right side
and although I has scraped the carbon out of the ring lands on the
piston, there was a little tight spot that kept the ring from seating
deep into the ring land groove. A little filing of the groove
finally allowed the ring to compress properly and the cylinders
dropped down easily. I had the cylinders honed before installation
and there were a few scratches on the right side where the broken
piston ring was rubbing up against the cylinder wall, but it should
be okay to run that way, I hope.
I
think the machine shop did a bit of bead blasting of the combustion
chambers on the head as it was all shiny and clean. I came up with a
good used later model camsprocket and matching camshafts to replace
the 3 lb original camsprocket. The rocker arms still looked good, so
they were reused with the pins and the valve springs and all the
valves, after they were cleaned on the wire wheel.
The
completed head was gently slipped back over the studs and the
camchain pulled up to meet the camsprocket. In order to assemble the
engine with an endless chain, you must install the inner cam bearings
in the head, then slip the camchain over the tapered side of the
sprocket in order to finally lift it over the sprocket teeth. With
the right side piston at TDC, the camsprocket flat with the punch
mark must be leveled with the cylinder head surface and then the cams
are inserted from both sides, as you match up the master spline
sections together. The cylinder head must be secured with a couple of
short 3/8 drive sockets and nuts on top to compress the head and base
gaskets enough to allow the camshafts to be inserted into the
camsprocket. Care must be taken to index the point cam mark at the
top as the right side cam is driven into the sprocket splines.
It’s
a tricky business, doing the endless chain, but reduces the chances
of a master link failing. It is hard to find new camchains that come
with a clip-type master link now. I have found that OEM Honda master
links will fit into some of the aftermarket camchains once the chain
is separated. Honda’s 250-305 engine share the same camchain
length as the 350 twins and SOHC 750s, which all run endless chains.
Chassis
powdercoat
Once
I finished disassembly of the chassis, it was time to haul it all out
to the local powdercoating shop to make it all black again, except
for the fenders and side covers. I had to have a little piece of the
chain guard bracket re-welded and the fork crown holes were welded up
and the local polishing shop finished the welds off so it looks like
a 1961 crown, instead of a 1962 version.
All
of the nuts and bolts came off and went into a big bin for cleaning
and reassembly. What I failed to notice was that the shocks were held
onto the swing arm with 8mm bolts instead of the normal 10mm types.
After the shock covers came back and the re-chromed lower covers were
all installed, I noticed that I didn’t have the correct lower shock
bolts. I ordered some grimy used ones from an eBay seller, but in the
meantime I discovered a pair in a separate box of parts. After I
cleaned them up on the bench grinder wire wheel, I discovered that
they didn’t fit the shocks! I had noticed that the original shocks,
which have alloy covers were steel instead, but it finally dawned on
me that these shocks were from a CB160!
The
problem with most powdercoating shops is that they are not fully
tuned into which parts need to be covered up and which are not. I
spent a couple of hours removing powdercoat from the inside of pivot
holes, the steering stem lock housing and worst of all the rear shock
bushings on the swing arm were burnt out and all that was left was
the outer sleeve, still stuck in place and powdercoated around the
edges.
I
attempted to cut out the sleeve with a hack saw blade in two places,
180 degrees apart, but that didn’t work. Finally, I dug out a box
of seal and bearing drivers and in the bottom was a small chromed
steel slug with a hole in the center. The OD matched the OD of the
bushing sleeve.
BYW,
the little bushing tool had RH initials inscribed on the edge. This
was part of the tools and equipment that I received from Bob Hansen,
the “father” of the CB750 prior to his passing a number of years
ago. I didn’t remember even having it, but I think the lower swing
arm bushing for the CB750 rear shocks is the same as the CB77 part.
So, thanks Bob, for helping me out in a difficult situation.
Not
having a hydraulic press left me with few options. Finally, I used a
tapered drill bit and knocked a small edge into the bushing shell.
Using a deep socket to allow the bushing sleeve to move into, the
little steel slug was positioned into the tapered hole and the swing
arm held together all with both hands in my bench vise and I managed
to square up the tool and tightened it all up. The vise handle is
only a foot long so didn’t have enough leverage to apply serious
pressure to the little tool piece. Once it was secured in the vise, I
grabbed my trusty, spare CB77 fork tube to apply some more force to
the vise and it slowly pushed the tool through the swing arm hole and
out came the bushing sleeve! I applied the same strategy to the
opposite side bushing sleeve and finally the holes were cleared out
so new bushings could be installed. I was able to use the vise to
push the new bushings in place. You have to install them flush with
the swing arm surface or the shock clevis won’t fit down on the
shock mount.
There
were more difficulties with the steering damper parts. The bottom of
the steering stem was not covered before coating, so more filing and
grinding was required in order to fit the damper parts on the bottom
of the stem. Honda used several different parts for the steering
damper, including the bottom spring and the spring holder that the
damper shaft is threaded into.
I
have to turn the frame upside down in order to install the swing arm
and the centerstand parts. Somehow I wound up with two of the longer
centerstand bolts, instead of one short and one long on the side
where the side stand bracket attaches to the frame. Sifting through
various boxes of parts failed to unearth the short bolt, so I had to
order one up from an eBay seller in TX. The bike was missing the
centerstand when purchased, so I had to rob one off of the rolling
chassis that I picked up in N. Cal.
There
should have been a correct set of bolts on that bike, but the short
one went MIA, so things have slowed down until a new one arrives.
Installing the centerstand is tricky on these bikes, as the spring
seems to be way too short when using a spring installation tool. I
had found in the past that I could attach the short bolt loosely in
the right side and hook the spring to the left side anchors, then use
the centerstand as a lever to stretch the spring out enough to allow
the long bolt to go all the way through the frame and bracket holes.
I
did install a tapered steering head bearing kit for the stem to do
away with the 37 little #8 balls from escaping in the original
steering races. The upper stem bolts and hardware were NOS pieces
from the Colorado parts stash. Those parts, in addition to the box of
CB77 spare bits that I have acquired over the years are finally being
put into play for this oddball project.
The
wheels and brakes were all disassembled and cleaned. I actually
swapped out the wheel assemblies from my parts bike stash from N.
Cal, as the original rims were very rusty. I discovered a set of
re-chromed spokes that had been stored away, so cleaned up the rims,
de-rusted the brake drums, wire wheeled the brake linkages and
reassembled the brake panels. I wound up using the ancient, but
unused Michelin tires that were parts of the N. Cal stash, despite
the shipping tag that showed a 1997 purchase date! The beads were so
strong that I had to have a motorcycle shop install them. The bike is
being revived not fully restored, so I am cutting costs where I can,
just to get it running once again.
The
assembly went slowly, as the needed small parts drifted in from eBay
sellers, CMSNL and other sources. Once the centerstand, sidestand and
swing arm parts were attached, the frame was spun over and supported
by a long pair of tie-downs that were hung from an overhead rafter. I
slid the rear wheel into the swing arm, temporarily, to help balance
out the weight of the front forks and wheel. As that progressed, I
had to figure out how to mend the missing battery box piece, which
attaches to the front of the rear fender. A trip to Home Depot
yielded a piece of sheet metal which I cut down to the size of the
battery box and then flared one end to accept the fender bolts.
The
holidays interrupted the powdercoating process, so the silver parts
were delayed a few days. When they were finished, I was able to
attempt the rear fender installation after removing the rear wheel
again to access the forward fender bolt holes. I slid the metal
repair patch back towards the fender and marked the holes. I drilled
the new holes in the patch piece, bolted up the fender to the edge of
the sheet metal and then used GOOP to glue the patch piece down to
the remaining part of the battery box. Not pretty but you won’t see
it, unless you remove the battery.
I
rolled the chassis back off the bike rack and wheeled the engine over
to install in the frame. Juggling a 115 lb engine on a small floor
jack is always a challenge, but I was able to maneuver the jack
enough to start the engine upwards into the frame mounts. Once the
holes start to line up, a few big Phillips screwdrivers poked into
the bolt holes help keep the installation process going until all the
mounting bolts are finally installed. Once the engine was put in
place, the rolling chassis was rolled back onto the bike rack for
more part installations.
TBC
Bill Silver
aka MrHonda
www.vintagehonda.com
