83 Honda 750 Shadow

Ok, Mr. Kritter,

I've cleaned the carbs, reset the floats and cleaned the idle screw
areas. It still seems like it is losing power about the top end of the
throttle, although it runs better than before I cleaned the idle jet
areas. It still has trouble up hills, and the smoothest ride is in 4th
gear. I haven't adjusted the pilot/idle screws from their factory
settings yet. Factory is 2.75 turns out.

Have ye any suggestions?


Tim

 

As I said before, 2.75 turns out is quite a bit for idle jets as big as
your Shadow has. The strategy of adjusting the idle jets is to warm the
engine up and start at about 1.5 to 2 full turns out from lightly
seated and generally screw the pilot screws IN 1/4 of a turn at a time.
This should result in the idle speed getting FASTER and you should have
to turn the master idle knob counterclockwise to slow the engine RPM
down. Then you would go to the other carburetor and repeat that
adjustment so you wind up with the fastest smooth idle speed for the
smallest amount of butterfly opening...

The mistake that amateur tuners make is that the OPEN the pilot screws
too far and the engine speed slows down and they think that the idle
mixture is too lean, so they open the pilot screws even more, and the
engine runs even slower. So they adjust the idle speed higher with the
master idle knob. This opens the butterflies a little more and it
uncovers the transition ports that are supposed to help the engine
accelerate just as you crack the throttle. With the master idle knob
adjusted that high, the engine is always running on the transition
ports at the smallest amount of throttle you can give it. The engine
sound is dull and thudding and maybe the engine RPM will hang up at
high RPM when you suddenly close the throttle. So, are the spark plug
insulator noses all black with dry soot after the engine has been
idling, or what?

If the idle mixture is really too rich, the exhaust sound will be
"toot-toot, toot-toot, toot-toot" until you open the throttle a lot and
blow the excess fuel out of the cylinder...

The pilot mixture does have some effect on cruising at 1/8th throttle,
but once you're past 1/2 throttle, you're running on the jet
needle/needle jet orifice. Is the jet needle clip in the right groove
(usually 2nd groove from the top), or does the jet needle even *have*
any grooves?

Somebody in this NG was talking about how his jet needles were
installed with the plastic spacer washer on top of the jet needle. That
plastic washer is supposed to go *under* the top of the jet needle.
Assembling those parts in the wrong order would make the carburetors
very lean around 1/2 to 3/4 throttle...

What does the engine sound like, a flat drone when you're trying to run
at higher speed, or does it miss and cut out or stagger and surge?

Have you checked the compression on that machine lately?

How old are the spark plugs, anyway?

What do the spark plugs look like after a high speed run? Are the
insulator noses sooty black? That's rich mixture. Wet black is oil
burning or really excess gasoline coming through the main jet, light
grey or tan is correct fuel air mixture, or are they bone white and
rough looking? Spark plugs with white insulator noses indicate the
mixture is very lean. Any little black specks that look like grains of
pepper? That's from pre-ignition. Hopefully, there are no tiny silvery
aluminum balls
stuck to the insulator noses. That indicates a seriously lean mixture...

 

T: the jet needle doesn't have any grooves, it is held in place by a
spring and a plastic holder that sits over top of it. there is no
plastic washer, just the plastic holder. later models had the washers i
them, but not this year model

T: it will accelerate decently, until a certain point, then it seems to
miss and cut. usually at that time, i can shift up to the next gear to
maintain some acceleration. on flats and downhill isn't bad, but uphill
is torture.

T: I haven't checked compression yet, was talking with my buddy the
other day who is coming over next week with his compression gauge.

T: spark plugs were replaced in May, but I used autolites. I am going
to get NGK next paycheck. They only have about 30-50 miles on them. I
haven't pulled them back out to check them for indicia of problems, that
is on Sunday's agenda.