both sets, current and spare, are 657B and 4 clip positions...
I haven't pulled the carbs yet. The reason I want to is that I relied on someone else to clean and rebuild them. After all I've done with this bike, other people always seem to fail me. And now I just want to verify that the carbs are perfectly clean and rebuilt as they should have been. I've seen evidence already that proves the contrary...blocked air passages to be specific.
Yes.. that is valuable info and you cannot depend on others unless you know them for many years.
Check out this little exerpt from HondaMan.
657 A & B's
HondaMan
Honda's recommendation on the "sooty 657A carburetor calibration" was to first try dropping the needles
one notch. If that wasn't enough, to go to the 110 jet was the next step.
In actual use, dropping the needles has more effect on daily riding than the smaller jet, since you're riding
most of the time in the lower 1/4 throttle range where the combined too-rich idle and too-rich needle are
causing the issue. Thus, dropping 5 on the mainjet will only drop it about 0.5% until the slide clears the
wasp-waist in the throat: then it goes to about 2.5%. Dropping the needles drops it a little over 1% per notch.
The early K1 pipes (HM300) had no baffles inside. The later ones had one baffle near the upsweep corner(s)
on each pipe, which increased the backpressure enough to make the 115/notch4 calibration too rich, and
the 'unofficial advice' was issued via the factory reps' word-of-mouth. BTW: the 115 was the original jet in
the 657A carbs.
Some other things to watch for on the 657A: the air screw seats were thinner than the later carbs. So,
turning the air screws in to seat, then out 1 turn, slowly widens that seat. Today, you may find that you
are better off with about 7/8 turn instead. This seat got about 0.5mm thickerin the 657B, among other things.
Also, the 657A carbs often had 25mm float levels, and this level was set from the tiny flat pedestal
that is right alongside the floats: not by using the notch on the sides of the carb body. If you attempt
to meausre a 657A carb that is properly set from those side notches, it will appear to be set at 24mm,
which leads some folks to adjust it. Don't...
The 657A and the original 4-cable K0 carbs both suffered very soft brass tangs on those floats that
were also made from brass. Check for a tiny dimple in the float tang of each one, and polish it off
with either a needle file or such, then reset the float level. This little dimple makes the float valves
stick and occasionally overflow the carbs for no apparent reason. The 657B until K3 was also
famous for this, but had plastic floats.
LUCKY now... Just thought I would throw that in there to think about.
A little history never hurts, but I have not see those brass floats with the dimples since I was 17 years old. That was back in 1969?
