Setting idle mixture screw on old Hondas

 Hi --

I've got a 1972 cb350 (twin) with idle issues that I'm messign around with
and trying to correct.

In the process of this, I tightened, then slackened off the idle mixture
screws on both carbs. I actually don't know where to set them.

Is there a standard setting, ie. 2 full turns from lightly seated, or does it
depend on other factors? Thanks much, MW

--
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 Albrecht wrote:

Albrecht, thanks, as ever, for your comprehensive response. I'm nothing if
not amateur, unfortunately.

As a result of my fiddling, I've done the following:

I found an old chart of settings at this URL:

http://oldmanhonda.com/MC/DataTable.html

So I set the idle mixture screws at one full turn from lightly seated, on
both sides.

Then, I fiddled with the idle adjustment screws on the throttle. Both sides
are now fully open (ie. maxed out).

Result: An idle at about 1100 rpms, which would be perfectly satisfactory IF
the bike wasn't now very sluggish and unresponsive. It sputters badly, and is
really unresponsive to the throttle.

The torque seems cut in half -- which leads me to think I've fouled a plug
now somewhere in this process. There still seems to be a steady rhythm of
exhaist coming out of both pipes at idle, but I'm not sure that means
anything with regards to a fouled plug/cylinder not firing.

And I'm no mechanic (obviosly) but it strikes me that the idle throttle screw
shouldn't need to be maxed out to maintain an idle speed of 11 rpms.

Now what, I'm not sure. I just had my carbs rebuilt, but, I'm starting to
think, maybe not very well.

I'm going to go back and study your lenghty reply and try to implement some
of the things you've said here. In the meantime, any advice with respect to
the further details above would be GREATLY appreciated. Many thanks once
again, MW

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Ah, but are both exhaust streams HOT....or is one just luke warm ????


Right on!


Maybe but B4 you start tearing the carbs apart again, I'd certainly check
the plugs and check for spark on both sides.  Then I'd check the boots
between the carbs and the engine for leaks (which is a common problem on old
bikes that have had the carbs removed).

Good luck!

Oh, and another possible clue to a dead cylindar.........with bike running,
adjusting the idle mixture screw on one side has absolutely  NO affect while
the one on the other side has a GREAT affect.