Posted by Eigenvector on November 24, 2007, 1:04 pm
My CB550 has 4 carburators that link to each cylinder. The air intake
enters a chamber which splits into 4 inlets to each carburator. Lately I've
been seeing gas dripping out of the air intake chamber like the carburators
were overflowing and draining into the air intake. I thought I remember
someone here saying that occasionally the needle valves can stick and
rapping the carburators can get them unstuck. That's what I'm suspecting
here, that one or two of the needle valves is stuck open and the float bowls
are overflowing into the air intake chamber.
Does that sound about right? I'd hate to have to pull that damn carburator
off again, it was a pain in the keister before and I doubt it will be a joy
this time. In fact I'm seriously considering modifying the air intake
chamber to something a bit less difficult to work with. But if the needle
valves are shot I'll have to swap them out or overhaul them.
It was purring like a kitten before Thanksgiving, so it has to be just a
stuck valve or ice in the valve.
Posted by George R. Young on November 25, 2007, 9:32 am
> My CB550 has 4 carburators that link to each cylinder. The air intake
> enters a chamber which splits into 4 inlets to each carburator.
> Lately I've been seeing gas dripping out of the air intake chamber
> like the carburators were overflowing and draining into the air
> intake. I thought I remember someone here saying that occasionally
> the needle valves can stick and rapping the carburators can get them
> unstuck. That's what I'm suspecting here, that one or two of the
> needle valves is stuck open and the float bowls are overflowing into
> the air intake chamber.
>
> Does that sound about right? I'd hate to have to pull that damn
> carburator off again, it was a pain in the keister before and I doubt
> it will be a joy this time. In fact I'm seriously considering
> modifying the air intake chamber to something a bit less difficult to
> work with. But if the needle valves are shot I'll have to swap them
> out or overhaul them.
>
> It was purring like a kitten before Thanksgiving, so it has to be just
> a stuck valve or ice in the valve.
>
>
>
If you run the carbs dry (e.g. by blocking the vacuum feed to the
petcock), the needles will open as the floats fall, and the debris which
is stuck in them will hopefully fall out. Or at least it may get washed
out when you reconnect the petcock vacuum feed and gas rushes in the next
time you start.
Anyway, it's easy.
Posted by Eigenvector on November 25, 2007, 8:57 am
>> My CB550 has 4 carburators that link to each cylinder. The air intake
>> enters a chamber which splits into 4 inlets to each carburator.
>> Lately I've been seeing gas dripping out of the air intake chamber
>> like the carburators were overflowing and draining into the air
>> intake. I thought I remember someone here saying that occasionally
>> the needle valves can stick and rapping the carburators can get them
>> unstuck. That's what I'm suspecting here, that one or two of the
>> needle valves is stuck open and the float bowls are overflowing into
>> the air intake chamber.
>>
>> Does that sound about right? I'd hate to have to pull that damn
>> carburator off again, it was a pain in the keister before and I doubt
>> it will be a joy this time. In fact I'm seriously considering
>> modifying the air intake chamber to something a bit less difficult to
>> work with. But if the needle valves are shot I'll have to swap them
>> out or overhaul them.
>>
>> It was purring like a kitten before Thanksgiving, so it has to be just
>> a stuck valve or ice in the valve.
>>
>>
>>
> If you run the carbs dry (e.g. by blocking the vacuum feed to the
> petcock), the needles will open as the floats fall, and the debris which
> is stuck in them will hopefully fall out. Or at least it may get washed
> out when you reconnect the petcock vacuum feed and gas rushes in the next
> time you start.
> Anyway, it's easy.
We'll see about that. I can turn any simple job into one that makes the
neighbors shut their drapes and grab their shotguns just in case...
Posted by Outback Jon on November 25, 2007, 6:47 pm
George R. Young wrote:
>
>> My CB550 has 4 carburators that link to each cylinder.
WOW! 16 carbs? Man, I'd hate to do the synch on that... :)
The air intake
>> enters a chamber which splits into 4 inlets to each carburator.
>> Lately I've been seeing gas dripping out of the air intake chamber
>> like the carburators were overflowing and draining into the air
>> intake. I thought I remember someone here saying that occasionally
>> the needle valves can stick and rapping the carburators can get them
>> unstuck. That's what I'm suspecting here, that one or two of the
>> needle valves is stuck open and the float bowls are overflowing into
>> the air intake chamber.
>>
>> Does that sound about right? I'd hate to have to pull that damn
>> carburator off again, it was a pain in the keister before and I doubt
>> it will be a joy this time. In fact I'm seriously considering
>> modifying the air intake chamber to something a bit less difficult to
>> work with. But if the needle valves are shot I'll have to swap them
>> out or overhaul them.
>>
>> It was purring like a kitten before Thanksgiving, so it has to be just
>> a stuck valve or ice in the valve.
Try this. Start it up, and then turn the petcock to "OFF". If, after a
few seconds, it starts running right, your problem is either a stuck or
leaking float valve (or float), or the floats are misadjusted. It's
fairly easy to bend the floats into the wrong position when you have the
carbs off and open.
>
> If you run the carbs dry (e.g. by blocking the vacuum feed to the
> petcock),
The CB550 has a manual petcock. Simply turn it to "OFF"
the needles will open as the floats fall, and the debris which
> is stuck in them will hopefully fall out. Or at least it may get washed
> out when you reconnect the petcock vacuum feed and gas rushes in the next
> time you start.
>
> Anyway, it's easy.
OK, that's just wishful thinking. Although doing what George suggests
*is* easy, it probably won't fix your problem. But give it a shot, as
it might, and it won't hurt anything.
I'm not sure about the 550, but on my 750, I could get the float bowls
off without removing the rack of carbs. Might let you get things open
enough to spray the hell out of them with some carb cleaner.
--
"Outback" Jon - KC2BNE
outback_jon@ver.no.sp.am.izon.net
AMD Opteron 146 (@2.8) and 6.1 GHz of other AMD power...
http://folding.stanford.edu - got folding? Team 53560
2006 ZG1000A Concours "Blueline" COG# 7385 CDA# 0157
1980 CB750F SuperSport <== For Sale $1200
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> enters a chamber which splits into 4 inlets to each carburator.
> Lately I've been seeing gas dripping out of the air intake chamber
> like the carburators were overflowing and draining into the air
> intake. I thought I remember someone here saying that occasionally
> the needle valves can stick and rapping the carburators can get them
> unstuck. That's what I'm suspecting here, that one or two of the
> needle valves is stuck open and the float bowls are overflowing into
> the air intake chamber.
>
> Does that sound about right? I'd hate to have to pull that damn
> carburator off again, it was a pain in the keister before and I doubt
> it will be a joy this time. In fact I'm seriously considering
> modifying the air intake chamber to something a bit less difficult to
> work with. But if the needle valves are shot I'll have to swap them
> out or overhaul them.
>
> It was purring like a kitten before Thanksgiving, so it has to be just
> a stuck valve or ice in the valve.
>
>
>