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
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