Well, between a little jaunt off to Cozumel last week and rounds of parts cleaning, sorting, procuring and assembling, the weeks have just flown by.
I rounded up a local man who had a mobile soda blaster setup and we attacked the engine cases, cylinder head, covers and my rare, alloy CB77 front fender (so I could ship it to metal wizards for repairs and dent removal). The soda blast came after car wash cleaning and steam cabinet cleaning to get all the oil out of the pores and peel off the spray paint. Once the parts were cleaned off, I was able to begin engine building, which included a replacement crankshaft, new camchain/primary chain, X’ing the transmission gears, new seals, knocking off the high spots on the cases with a large, single-cut file, reassembling the shift drum/forks and transmission gears, along with some new transmission bushings. The primary chain was replaced with a rare NOS spare and a new wide-style camchain tensioner will be used on the cylinder block.
Once the bottom end was assembled, the clutch was the next focus of attention. I tried mixing-matching some early and late clutch plates, along with using an older hub which uses three retainer spring wires. I used some “white” clutch springs, but the clutch pack wound up with six plate sets, instead of the usual five, so the total stack height is a little bit more than normal.
I had sent the cylinders off for 1.00 re-boring with new pistons, but the machine shop called back to say that the sleeves fell out when he took it out of the steam tank! Also, both sleeves had some fractures at the lip edges, so they were junk. A quick search on-line found a set of .25 250cc cylinders from a large-scale eBay seller in OR. I paid for them and had them shipped to the machine shop for work while I was gone on vacation. When I returned, the machinist said that he had swapped out the cylinder sleeves from the purchased cylinder block cleaned and set them with Lock-Tite, then bored the liners out to 1.00mm oversize, then put the cylinders in a mill to flatten them out again.
On to the cylinder head, which had a worn camsprocket (loose rivets) and pitted camshaft lobes. I dismantled it all, cleaned the valves, lapped the seats and reassembled it all with a couple of new cam bearings and a NOS camsprocket from stock. I re-used the rocker arms and shafts and buttoned it all up for installation.
With new pistons/rings and cylinders bored to size, the next steps were to install a new camchain guide wheel and camchain on the crankshaft. I run a piece of 22 gauge electrical wire through the end of the chain with a knot tied in the end to retain the chain while all the parts get loaded up vertically. The pistons were installed with new pins/clips and ring gaps all were right at specs. Unfortunately, when you bore the cylinders out to 1.00mm the nice beveled edges at the bottom of the sleeves almost disappear and they are instrumental in helping to nudge the rings into the piston grooves during installation. It probably took about 15 minutes to work the rings into the bottoms of the liner bores without breaking a ring. Once the pistons are secured in their bores, the process speeds up with new gaskets, o-rings for the locating knock pins and then the head is slid down over the studs and down flush onto the cylinder head gasket. Even with the cylinders being decked a few thousandths of an inch, the camchain didn’t want to hook up until I put a nut and sleeve over a stud to help clamp the head/cylinder block down sufficiently to allow the camchain to be connected with the master link.
Once the motor was all tied together, it was a quick “clean and jerk” move to get it off the bench and onto a little wooden, 4-wheeled dolly for transport back to the chassis. If you have read my previous postings about doing this exact job on an early model CL77 last month, you know that reinstalling the motor and all the chassis parts is a lengthy and exacting puzzle to assemble. With most of the major components reunited, I had to install the E-ignition system components on the chassis and cylinder head, all wired up properly.
The bike fired up after about five kicks, but was spitting back through the air filters and running rather poorly at first. It appeared that something was going on with the right side carburetor, so I finally removed it for replacement of the float valve, reset the float level and rechecked the idle jet for signs of plugging. Nothing seemed unusual, until I put it back on the engine and fired it back up with the air filter still removed. I could see the slide and needle moving up and down, but I didn’t see the edges of the needle jet in the carb throat! I had the carb bodies completely torn down and apparently forgot to install the needle jet in one side. Another “Senior Moment” I guess, but it was a quick fix and the engine fired back up sounding crisp and clean, finally.
Once the whole bike was assembled, I rolled it out into the driveway and headed out for its first test-run. The engine is very quiet and seems to be carbureting correctly. However, a combination of my hybrid clutch and worn out clutch release mechanism components seems to be affecting the clutch release action. I discovered that the clutch cable joint is the wrong one for the k/s cover, thus imparting some bending/binding in the cable as it spans the distance from cable joint to the clutch lifter arm. The clutch adjuster was installed upside down and has apparent wear on the threads, so that will have to come back out and be replaced along with the cable joint.
A final challenge is that the bike’s charging system isn’t charging. I originally thought that the rectifier wasn’t grounded or was defective, but pulling the stator lead connections apart and testing each “leg” of the wiring showed two dead leads out of the three. The kickstarter cover has to come off anyway, so the stator will be checked and either repaired or changed out for a good one.
Never a dull moment, when trying to revive these old bikes, but the sound and the appearance of this one will be attracting many approving smiles in the weeks, months and years to come.
Bill “MrHonda” Silver