My friend Gilles has 15 or so various vintage bikes, mostly Hondas and he tries to keep the herd exercised regularly. He picked up a very sweet-looking Black/green 1973 machine with low miles and with stock 4:4 exhaust pipes. The overall appearance is very good with shiny chrome and bright instruments.
The bike exhibited the sticky front brake problems that affect so many 40+ year old original Hondas that haven’t had regular maintenance, but that isn’t a huge task to resolve. He lives up in San Diego’s N. County coast area, which is about 50 miles away from me. Fortunately, our friend Randy Troy is an excellent ace mechanic and lives out to the east of Gilles in Valley Center. Randy did the brake work and then noticed that the idle mixture screws required shutting them all the way OFF in order to idle properly. This is not a good sign and can only be remedied by carburetor removal and inspection.
I was up in N. County for my monthly chiropractor appointment, which is about 20 minutes away from Gilles, so I stopped by to have a look at the bike and agreed to bring it back home for some TLC and necessary repairs. After he bought the bike, I suggested that he pick up an electronic ignition system to eliminate the points and condenser original parts. He picked up a system from 4into1.com, which I wasn’t familiar with, but most of all of them are pretty much the same, these days. There was also a burned-out headlight bulb issue that needed to be addressed. No big deal, right?
Despite a “new battery” in the bike, Gilles has to kick start it as it wouldn’t hold a charge. I put the battery on my charger while I installed the ignition system, then tried to use the electric starter to light it off, but the voltage plunged from 12.6 to 4 under load. The kickstarter was working, but someone had taken it apart, apparently, as the mechanism wouldn’t stay retracted properly. The solution for that issue was just a 5/16” steel ball to help retain the kickstarter arm properly.
I had difficulty in setting up the ignition system as the LED light was coming on way after the TDC T mark, much less way after the F firing marks. I slotted the backing plate, filed down the protruding edges and finally got it to time correctly. The battery kept bouncing back to an indicated 12.6 volts, but there seemed to be no current available under load. The bike did fire up on the kickstarter and on a hunch I checked the charging system voltage and it was immediately pushing 15 volts at about 4k rpms. I surmised that the high voltage had popped the low-beam filament, so I shut it all down.
I ordered a new sealed beam from 4into1.com, which came in an OEM box for about $80. Going on eBay to search for the part number turned up several listings where people were asking $300 for the same part! The new bulb arrived safely and was installed with no problems. I had to think about how to rein in the voltage output, so removed the voltage regulator for inspection. There is one small adjustment that can be made to change the tension on the point set, but I could see that someone had been in there before tweaking the contact mounts and the adjustment stop. I bent the stop down ever so slightly and reinstalled the voltage regulator. Firing the bike back up on the old battery ( a new one was ordered), the voltage rose up into the 13v range and held steady. I had ordered a solid-state regulator-rectifier unit to replace the mechanical point voltage regulator, but it may not be needed.
Moving on to the carburetor problems, I extracted the carb rack from the engine and put it on the bench for inspection. I removed the idle jets and poked the holes open with my tapered reamers and then looked at the array of floats and how they were adjusted. The floats on these carbs are plastic and have a flat bottom that winds up parallel with the carburetor body bowl surfaces when the 21mm float level setting is correct. What I encountered were floats that were more like 45 degrees away from parallel and were about 31mm at the high point. Yikes! Who would do something like that and think that it was okay? After resetting all four float levels, I replaced the main jet o-rings which may have been original as they all looked pretty smashed, but were still sealing. I did a quick rinse of the bowls and put it all back together again.
With carbs mounted back on the bike, the engine fired back up (still kickstarting it) and once the mixture screws were set back out to 7/8 – 1 turn out, the engine settled down and idled smoothly once again. A test ride showed improvements in the overall power curve and throttle response, but in the end these bikes are pretty underpowered for a 350cc machine, but they do have a great visual presence and sound lovely running down the road.
With a fresh battery, a repaired kickstarter arm, the voltage under control, a new headlight and carburetors that are set back to OEM specs, the little beauty is ready to go back home and be enjoyed along the coastal strip of San Diego’s N. County beaches.
Bill Silver aka MrHonda
8/16/23
PS
No good deed goes unpunished….
After delivery to Gilles, where we met about halfway between his home and mine, he rode off to cruise the coastal highway only to have the electronic ignition die about 10 miles up the road. I was almost all the way back to my home and had to U-turn and pick up the bike again. Fortunately, the bike died about a quarter mile away from where his wife had stopped to grab lunch, so she took him back home. I ordered a tried and true Dyna ignition kit from 4into1.com and that should solve that problem.
There were signs of an oil leak as well when the bike was parked. Removing the left side sprocket cover revealed a little bit of a leak coming from the threads of the oil pressure switch. That was remedied with some Teflon tape and solved the little oil leak problem.
While it was here, we decided to do an oil and filter change. There was a bit of weeping at the drain plug, so I installed a new one with a fresh, new aluminum gasket. The final check ride showed a dry motor on the bottom, instant starting even without the choke and a nice smooth ride again. It could use some quality rear shocks and a little front fork work to smooth out the ride quality, but it is what it is, as it was from the factory 50 years ago.
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