I have a '65 CL 77 that I just bought and started to sort out. It had no air cleaners, and being a tight-ass, I bought some of the cone-shaped filters that fit right on the carb inlets. I have not oiled them yet. As I was working through things, I was having trouble getting the engine to idle. (135 mains, 40 pilots, needles down all the way) To check slide operation, I removed the air cleaners, and the bike came down to idle. Thinking I had unstuck a slide by putzing around, I reinstalled air cleaners. There goes the idle back out of control. Take off the cleaners, back down. Put the stock air cleaner tubes on, no effect; put the air cleaners on at the end of the tubes, idle zooms up again.
Wow..............I was impressed. If you have an engine that wants more air, these type of filters will do it. I realize it's simple fluid dynamics, but just didn't think that these would work that well for being 'cheapies'.
BTW.............what would be your experience for a non-paper replacement filter that doesn't work 'so good' ?
Interesting Discovery.....or notVery, very interesting.
When I was living in Japan I pulled a CB350 out of the trash, got it running and rode it all over the place for a couple of years. However, that bike would also rev out of control and would never hold an idle. I checked everything to no avail. Literally drove me crazy, as I, clearly erroneously, thought of myself as a fairly skilled mechanic. However, I never tried running it without air cleaners.... Reading your travails, it occurs to me that perhaps the overly restrictive air cleaners you installed increased the vacuum in the carb throat, pulling more fuel into the engine....? Or, the reduction in intake air caused by the increased restriction is simply richening up the mixture, in which case you might try turning the air screws out a bit to lean things out again. Do what you've always done and you'll get what you've always had.
Nick, I was thinking the opposite..............that the design was causing more air. After oiling the filters, (too much), the bike didn't want to run at rpms. Need to clean and lightly re-oil. There were so many other issues, (sticking slide on one side, air leaks at the insulators, etc.), that have now been sorted out.
No time today, starting square one next time I get a chance to work on it. Are you saying that with the carbs open to the air, it idles fine but when you put the air cleaners on, the idle speed goes WAY up?
If that's the case, there is something else going on there that you haven't found yet. Any restriction to the air flow will cause the RPM to drop and the engine to run richer. You probably know all this already, but....
The mounting faces of the carbs on these old Hondas are invariably warped from being over-tightened, long years of misuse, etc. A must do for any rebuild is to put some wet/dry paper on a piece of glass or surface plate, squirt some WD or oil on there and rub the carb mating surface until it's completely flat. Then make sure the O-rings stand well proud of the now perfectly flat mating surface. O-rings should be greased. Lock nuts (or at the very least lock washers) must be used when mounting the carbs. Tighten only enough to compress the O-rings. Slides should fall through the carbs with gravity alone. Remove all high spots on carbs or slides until they do. Lube the throttle cable, grease on inside of throttle barrel but not where it clamps to handlebars. It's okay to stretch out the return springs a bit too. To clean carbs, strip and soak in lacquer thinner (not solvent, not gasoline) for about 30 min., then blast out with compressed air. Do what you've always done and you'll get what you've always had.
Went through everything................bike starts, idles, runs perfect. Smooth at 50, didn't want to push it on the big shake-down cruise.
Stop at light, go to shift into second................no second. I've been taking short test hops on it before, never a problem. Once I get it all sorted.................................. BTW, checked plugs after getting home.......toasty tan. Tranny time.
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