QuestionThanks for the reply. I checked my caps to the plugs and the connection to the wire was corroded. After cutting them back and reattaching the bike seemed to idle better but the problem still persists when I give it any gas. It was tuned up by an ex-honda technician who had it running great but now he is moving away and I truly want to learn how to fix and maintain the bike on my own but this has me stumped. All the electrical connections seem good, the points plate is tight and the plugs are clean. I doubt its the coils. I've been through the carbs about 14 times and all seems ok there too. Any other suggestions?
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Followup To
Question -
Good Day. My 69 cb350 was tuned up and running great for around 20 miles or so and now it runs as if neither carb is getting enough fuel. It idles great but bogs when you start to give it gas. Strangly, when you start to throttle up, it seems to run on the one cylinder then switches intermitently to the other, back and forth. I have gone through the fuel system and it's clean, the carbs have been rebuilt, the floats work, both plugs are new and so are the points. Also, the left cylinder seems to not fire until the bike is warmed up. Can you help? thanks.
Answer -
Hi Andrew,
If you had a shop technician perform the tune-up, return the MC to the shop and complain a bit, respectfully.
The shop should take the come-back and correct the problems.
The problems could be as simple as a loose wire, or ignition plate screws loose, etc...
Respectfully,
Mark Shively
AnswerI suspect an ignition problem.
Test charging system and ignition system components for integrity & proper operation. Trace all electrical connectors and conductors for continuity and defects.
Inspect ignition and engine stop switches for corrosion or other defects.
Check all ground connections for clean and tight connections.
I need to perform a few tests to accurately diagnose the problem(s).
You should get your question in to expert Bill Silver. He specializes in these vintage models.
I copied the following tech file from the internet.
Respectfully,
Mark Shively
Honda CB/CL Tech Tips
CB350
The Honda CB/CL 350 is a parallel twin four stroke bike. A CB350 will have its exhaust pipes routed to the bottom of the bike on both sides. These machines are frisky little buggers. They're not low maintenance machines, but are nice town bikes that have the capacity to go long distances. I think these bikes are prime candidates for café racer modification.
Rebuilding
Pay close attention to the cam chain area. If the bike has been apart before, it was probably due to this thing. Replace it if necessary. Watch for galling where the cams run in the head. They’re not bushed and this can be something of a problem. Roller cam kits are available and are pretty damn trick. You'll probably have a hell of a time getting the case screws out. There are several tricks to remove these screws. A buddy of mine swears by reverse tap drill bits. Of course, this destroys the screw, but likely as not any technique for removing these fasteners is going to trash them. A good (Snap-On) screwdriver will deliver the torque needed to remove these screws. Heat, or as my pal Jon calls it, "The Blue Tipped Wrench" will make these screws much easier to remove, but watch the cases. Soaking them in some kind of penetrant for several days before the actual removal date will make your job much easier as well.
Charging System
This is the Achilles heal of this bike. There really isn’t much to it and if you run with the headlights on (it’s the law now, you know) you will easily bake, fry or otherwise sink your battery. The main problem is that these bikes were not designed to have the headlight on at all times. Only two of the three fields of the alternator are going when the headlights are off. All three work when the headlight is on, but in order to charge the battery, the revs have to be over 3,000. If you putter around town and never really open up the throttle, plan on having difficulties. The best thing to do is attach a spade connector link to both terminals of the battery and connect the battery to a trickle charger at least once a week. This will keep your batter from running flat on you and will keep your battery able to turn the starter.
Selenium Rectifier
This is something that’s probably gone south on your bike and you don’t even know it. You can replace it with a new one (big bucks) or with a little ingenuity, you can fabricate a block of Xener diodes or just retrofit a system from some other bike.
Starter
The free wheel system on the starter can eat itself without much warning so if your starter doesn’t engage or doesn’t spin the bike over with much ferocity, use the kick starter. Change the battery and if that doesn’t fix it, then you’re going to have to pull the flywheel/rotor assembly and fix the freewheel mechanism. Not a huge job, especially if you have a good torch and a slide hammer and a gear puller, but no so pleasant if you’re not so equipped.
Front Brake
Take care of it and it will take care of you. Strip it at least once every other year and don’t be afraid to use it hard.
Front Tires
In order for your brake to work, you’re going to need a decent tire on front. I should be something new and preferably not super cheap. The better the grip is, the better the stopping power.
Carbs
The vacuum diaphragms on the CV carbs are notorious for tearing. Handle with care. They’re about $50.00 each. The carbs on this bike are pretty straight forward otherwise. Check the inlet boots regularly. Be sure to use Loc-tite or some other thread locker on the choke butterfly valve screws. I blew up one of these bikes due to one of these things getting loose and into the intake valve.
Exhaust Pipes
The stock ones have rotted out by now. If you have a hole in the pipes, these bikes will not idle. Don’t even try to mess with it. It would be easier to teach a pig to sing. Get a replacement, or get some pipe bent so that you can do a two into one with a Supertrapp or something. Not only is that going to help your bike sound cool, but it's super-trick as well. As always, rejet when you touch anything in the intake or exhaust system
CL350
All information applies to this bike the same as the CB350 above. The major differences can be found in the side-exit pipes and the different torque curve. This was the street scrambler (early term for on/off road bike) version. Take your pick, they are essentially the same.
Courtesy of:
Tim's Motorcycle Page
http://www.tholt.com/moto.html
