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The CB77 suddenly seizes solid… We both get "screwed" but live to tell the tale…

Starter clutch screws backing out, damage shown, replacement parts and reassembly.
Starter clutch screws backing out, damage shown, replacement parts and reassembly.
Bill Silver

This 1963 CB77 was featured last year in another story. See: for details. The bike was pieced together mostly from leftovers around the shop and has been back a few times for spark timing/camsprocket replacements and odd oil/fuel leaks here and there.

The owner, Lea Dennis, has only put less than 300 miles on the bike, since it was finished, so I guess it is still “under warranty” from me. Old bikes have old bike problems, but normally a decent vintage Honda 305 twin is oil tight and fairly trouble-free, when set up correctly. We battled oil leaks at the tachometer cable connector for quite awhile, until I got a really decently-made reproduction cable. The clutch cover gasket seems to have a slight, but incessant drip and a forward engine case bolt started drooling oil down the front of the lower engine case.

After some six hours of engine pulling/rework/reinstallation, the bike was running pretty well as dusk settled onto San Diego. I know most of you are hating the weather anywhere outside the SoCal these days, but it sure helps me to get things done comfortably this winter.

The bike went out for a couple of test rides and I sensed some steering looseness in the front end, so came back and readjusted the steering head bearings to snug things up. Another test ride verified the improvement in the steering/handling and the motor was sounding crisp and clean when throttle was applied in any gear.

Approaching a freeway onramp, I moved towards the diamond lane (car pools and motorcycles) to bypass a line of cars in the other single driver lane when a sudden screech was heard from the engine and it seized up solid, skidding the rear wheel momentarily at about 20 mph. Having just been in the engine, my mind raced with all the potential failure mode scenarios associated with an engine seizure. Fortunately, the local neighborhood truck was available on short notice and my neighbor came along to help me load the bike from the edge of the freeway apron.

Once it was unloaded, I dove into pulling the motor out of the chassis, fearing the possibility of a broken camchain, seized piston, seized crankshaft bearings or who knows what. I can pull the motor out of the chassis in about 20 minutes now, given so much practice lately. Popping off the top cylinder head cover revealed… absolutely nothing wrong in the top end, but the crankshaft was jammed up tight. Luckily, the camchain link was nearly at the top of the sprocket, so it was easy to unhook and separate the camchain to allow removal of the cylinder head. Once the head was removed, the piston bores looked just fine, but the crankshaft was still not moving. My “logical” mind decided that something must have gotten loose in the primary chain, so the oil was drained and the engine turned on its side for clutch inspection. Again…nothing evident to cause crankshaft seizure. Moving the remains to the workbench, it appeared that it would be necessary to split the cases to determine what had gotten into the crankshaft bearings.

The starter motor must be removed to allow the engine cases to be split, so once it was pulled back, the last thing to remove on that side is the crankshaft’s magnetic rotor/starter clutch assembly. The rotor bolt was easy to remove due to the seized crankshaft condition, but as soon as the rotor puller was used to unseat the rotor from the crankshaft taper/keyway the mystery was finally solved. One of the three starter clutch retainer screws had backed out, digging into the face of the starter clutch hub and wedged it all tightly together, fixing the crankshaft in an immoveable position. With the rotor removed, the crankshaft turned easily, once again. I’ve been SCREWED by a loose screw (not the one in my head, either. Well, that may be up for discussion!). It was one of those times when you fail to listen to your intuition about what the true cause might be. The starter clutch had come to mind, but I was sure that I had rebuilt the springs and rollers and should have attended to the three screws, checking them for looseness or damage, which I usually do. This kind of failure is not uncommon, but I have never had it happen to me on a running engine, so had no reference point to consider when I heard that sound. I would have thought that the screw backing off would have given more of a warning prior to it jamming all the parts together so suddenly. Well, it didn’t and I wound up wasting several hours of unnecessary labor tearing down a perfectly good motor and then getting to put it all back together again, just because I overlooked the simplest of failure points. Had I started with the rotor, the motor would have stayed in the frame, intact and the repair would have taken about 15 minutes instead of three hours.

The motor was buttoned up about 8PM, just about four hours after the initial failure moment and subsequent rescue adventure. Fortunately, I was about five miles from home and had my phone with me. Interestingly enough, almost as soon as I had put the bike on the centerstand a SANDAG highway rescue truck pulled in behind me to offer assistance or at least safe passage to the other side of the ramp. Had I run out of gas, he would have given me a gallon at no charge! As soon as the bike was secured properly to his satisfaction, he headed back onto the freeway to help another stranded motorist. Moments later, an all-white CHP stealth car (most are black/white) swooped in and the officer asked if I was okay and had called for help. I assured him that I would have the bike removed quickly, which we did with in thirty minutes.

In the morning, the motor goes back into the chassis for the fourth time and I expect everything will be back to normal, once again (or whatever is normal for this persnickety Super Hawk). I am glad that this failure occurred with me in the saddle, instead of Ms. Lea D. It goes without saying that paying attention to the smallest details of these old bikes is critical to long-term reliability and overall enjoyment. Somehow, I overlooked the starter clutch screws and created an unnecessary adventure for this bike. Hopefully, this will be the end of the mechanical mishaps for this black beauty, so that Lea can ride with confidence in her vintage ride that she loves so dearly.

Bill “MrHonda” Silver

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