problem with my old 750

[harold95]

1980 honda cb750 custom
bike is completely stock, air and exaust.
here is what i have done:

clean and adjusted carbs, factory jets.
synced.
floats are NOT adjustable on these carbs.

new plugs. d8ea's

checked, a spare set of pickups and ohmed those, and checked my bikes
pickups.
they ohm out to spec. 530 ohms give or take.

adjusted the cam tensioners, both the front and the rear for both sets
of chains.

replaced the air filter.

here is what is happening.
idles like a dream, smooth as silk.
take it for a ride and when i try to w.o.t. to as i climb into the
6000+ rpm range,
things start going wrong, skipping, sometimes a dead skip sometimes i
can't even tell what is skipping and where.

just wont accelerate quickly and smoothly through the power bands.

used to be a time i could whine this bike right out to redline, (9500)
now it can barely do that without what seams like misfiring.

6-7 years ago i had replaced the coils and wires.
the wires seem like new, and show none of the usual signs of wear.

but how to test the coils?
could that be the problem? coils that act ok at regular rpms and even
under a heavy load but once they reach high
rpm speeds they start acting up?

i did check that the timing advance was free, springs and weight are
free and not bound up.

also the battery and charging system are up to snuff, i also have a volt meter
display right on the bike so i know its charging and putting out 14 volts.


thats my story........what do you guys think?

thanks,
Harold

[t4tommy]

Have you checked the timing on the advancers?
the spacing on the little hammers is important.

also I'd make sure the clutch cable has 1/8" of slack when it is let go... sometimes folks leave that tight and the clutch stays partially enagged. that causes slipping, sometimes only in the higher end... feels like the drivetrain is skipping in and out.

so in short:
check the points with a strobe.
make sure the clutch lever jiggles.

[blackhawkrider]

kinda sounds like some slides aren't operating right. Has the bike been sitting for a while prior to all of the work you did? What method did you use to clean carbs?

[harold95]

i took them appart, tops and bottoms.
replaced all the lower end seals and gaskets, needles and jets.

took the tops off and make sure the passages were clear by spraying carb clean through them.

what else would i be looking for if i were chasing a slide/carb problem?

the bike only sat through the winter with NO fuel/corn syryp/what we have for gas in it at all
i drained it completely dry.

3 years ago i completely tore down the carbs and soaked them in denatured alcohol overnight and rebuilt them from there.

it ran like a champ.

i didnt do that this time because other than a fuel leak between the piping in between th carbs, my only reason for doing what i did do to the carbs was because i was already there, so why not replace gaskets and seals.

the carbs themselves looked in good shape. fairly clean.

hope that information helps.

[harold95]

how would you set or adjust the hammers on the spark advance?
they have springs on them, and as far as i can see, there is no way to adjust them besides the usual method of setting your timing.

[harold95]

it was the coils!

it still had a hard time in the 8000+ range wot so i took the tops of
the cv covers off and cleaned the insides of them with 0000 steel wool
and oiled them lightly.

oiled the slide barrel itself also and took it for a long ride.

it works great!

haunting problem solved!