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From: billybuckshot on 16 Jun 2007 11:40
On Jun 16, 8:50 am, "fweddybear" <fweddyb...(a)cox.net> wrote:
> <billybucks...(a)gmail.com> wrote in message
>
> news:1181966566.992622.201820(a)m36g2000hse.googlegroups.com...
>
>
>
> > On Jun 15, 10:13 pm, "fweddybear" <fweddyb...(a)cox.net> wrote:
> >> <billybucks...(a)gmail.com> wrote in message
>
> >>news:1181949372.794478.70970(a)w5g2000hsg.googlegroups.com...
>
> >> > On Jun 15, 4:23 pm, MadDog...(a)yahoo.com wrote:
> >> >> On Jun 15, 1:18 pm, billybucks...(a)gmail.com wrote:
>
> >> >> > I'm having a difficult time getting a friends Honda Cl450 to quit
> >> >> > fouling plugs. I'm familiar with vintage HDs and Brit bikes but this
> >> >> > old Honda is making me tear my hair out. I've cleaned the carbs
> >> >> > thoroughly and rebuilt them with new jets, readjusted the valves,
> >> >> > checked the points, compression (140 psi) but the bike fouls the
> >> >> > plugs
> >> >> > (black soot) within 10 minutes of start up. Other than replacing the
> >> >> > carbs completely, i'm out of ideas. Anyone out there familiar with
> >> >> > these old Hondas? Help is greatly appreciated. -Billy
>
> >> >> Probably an idle though after all this:
> >> >> "Are you sure you've got the proper heat range on those plugs?"
>
> >> > To answer everyones questions: i failed to mention that i replaced the
> >> > mixture screws. that didn't help. i also inspected where they seated
> >> > and the was no noticable damage.
> >> > i've also been through about 6 sets of NGK B8ES plugs, that are
> >> > constantly being cleaned in the bead blaster and returned back to the
> >> > rotation. I've also tried hotter B7ES plugs, no difference.
>
> >> How far out do you have the mixture screws? 1 1/2 turns should be a
> >> good starting point...
>
> >> Fwed
>
> > i had it about 1 1/2 turns out but have had it turned 3/4 to all the
> > way in and theres not much of a difference. the plugs just take
> > another minute or two to foul. the carbs have to be completely worn
> > out but i want to eliminate any possibilities that i've overlooked
> > something simple before i make this girl spend $200 and up on a set of
> > decent carbs.
>
> Does it start right up? If not, you may have an ignition timing
> problem....Still not sure what size you are using, but maybe try using
> smaller jets. Also, this may be a dumb question, but have you check the air
> passages or changed the air filter? You may not be getting enough air. I
> am gonna assume the bike is all timed properly too.
> I had a similar problem on another bike I have.....I ended up using a
> smaller jet, dialed in a different ignition timing, used a hotter plug, and
> also readjusted the air/fuel mixture screw. This took me a while to figure
> out the proper way..... my main issue was it was hard starting, but it also
> fouled plugs.
>
> good luck...
>
> Fwed


The mixture screw makes little difference. the engine fails to stumble
when i turn it in or out.

The bike doesn't have a starting problem. It starts right up, no
problem.

Right now the air cleaners are off, still fouls plugs. I even pulled
the mufflers, the plugs should've lightened up, they stayed black.

I bought a K & L carb kit and rebuilt the carbs . It came with
everything but the needle jet so I had to buy another kit that came
with needle jets.

I'd like to experiment with smaller jets but on e-bay they cost $20
each ($80) I already have $90 in carb kits invested in these
carburetors. I'm thinking about soldering up the jets and redrilling
them to a smaller size.

From: Albrecht via MotorcycleKB.com on 16 Jun 2007 13:18
billybuckshot(a)gmail.com wrote:

>The mixture screw makes little difference. the engine fails to stumble
>when i turn it in or out.

That's what happened when we tuned old two barrel carbs on our V-8's in the
1960's. We would turn the screw in until the idle got rough, then turn them
back out 1/4 of a turn and we were done tuning.

If your mixture screws are GAS screws like in a car carburetor or the typical
diaphragm type CV carb, the engine will drop about 50 RPM on a sensitive
tachometer when you reach the critical idle mixture level as you turn the
screws clockwise.

If the mixture screws are AIR screws, like the old style slide valve carbs,
the idle RPM will increase as you turn the screws counterclockwise, the idle
will gradually become unstable the engine will "hunt" for a stable speed.

GAS type idle screws usually have a spring, washer, and small rubber o-ring
on the end, but AIR screws are usually just pointed and have no o-ring.

Next time you pull the carbs off, set the idle RPM to the manual
specification first. Then look at the bottom of the throttle butterflies. The
butterflies should be almost completely closed and just uncovering the first
in a triangular pattern of
transition ports.

You might see half the first transition hole. Drag racers tuning GS1100
motors recommended setting the butterflies initially by looking at the half
of the transition port they could see, and the reflection of that half in the
shiny surface of the butterfly. If the hole appeared to be round, that was a
good start in what was called "bench synching" the carbs.

The transition ports are not controlled by the idle mixture screw, because
the
throttle butterflies are supposed to block of the transition ports until the
rider wants to accelerate away from a stop.

It's possible that the bottom of the throttle butterflies is worn out, or
maybe your engine has always been running on the transition ports because the
passages inside the carb bodies are plugged up.

Somebody once mentioned that even ultrasonic cleaning failed to clean out all
the passages of Honda vacuum piston carbs.

When I spritz out a set of carbs with Berryman B-12, I make sure that the B-
12
squirts out of every hole in the idle mixture circuit.

On a diaphragm carb, this means that the B12 has to go though the idle jet
and come out the air jet, it also has to come out the idle mixture port and
the three transition ports.

Sometimes I have to put my fingers over two ports to get the B12 to squirt
out another port.
>

>I'd like to experiment with smaller jets but on e-bay they cost $20
>each ($80) I already have $90 in carb kits invested in these
>carburetors. I'm thinking about soldering up the jets and redrilling
>them to a smaller size.

Can you read the numbers on the old idle jets? I know that Sudco
International has an online catalog of jets for Keihin carbs. This is helpful
if you know which style of jet you need. A dealer has to order jets from
Sudco for you.

And, you might learn something about the different styles of jets if you go
to www.factorypro.com. There is a section with pictures of different jets and
what bikes used them.

--
Message posted via MotorcycleKB.com
http://www.motorcyclekb.com/Uwe/Forums.aspx/tech/200706/1

From: Ken Abrams on 16 Jun 2007 17:39

<billybuckshot(a)gmail.com> wrote

> i tried that technique on a harley i had 16 years ago, it had a
> sticking valve. it worked great!
>

I just realized after my post that it could be getting oil from worn valve
guides too, in which case the "fix" won't do anything and you're back at
square 1.



From: billybuckshot on 16 Jun 2007 22:02
On Jun 16, 4:39 pm, "Ken Abrams" <harvest_t...(a)scum.suckers> wrote:
> <billybucks...(a)gmail.com> wrote
>
> > i tried that technique on a harley i had 16 years ago, it had a
> > sticking valve. it worked great!
>
> I just realized after my post that it could be getting oil from worn valve
> guides too, in which case the "fix" won't do anything and you're back at
> square 1.

I decided to take a break from the Honda today and finish up my 73
Norton fastback and 72 roadster. At least when Amal carburetors are
junk, its easy to tell.

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