Topic: One of my carbs looks yukky (photo)

[Henry Dorset Case]

yukky is what my neice called it and she is right. 

Its my '77CB400F

Even with the fuel turned off, often there is a leeedle puddle of fuel under the bike after a couple of days not riding.  It seems to be leaking from somewhere. 

Its the only carb that does it, and the sparkplug from that cylinder was carbon fouled before I  replaced them all. 

Bike seems a bit "soft" off idle but goes well enough up top (170kph indicated )

I suspect there is a blocked jet somewhere, or something stopping the needle from seating, or maybe some wear.

I suspect also that the bike sat for a long time on the sidestand, this carb would have been on the high side... maybe related, maybe not.

I am trying to leave pulling the carbs off completely until winter, in the meantime can anyone diagnose a potential problem, or is the only way the complete teardown.

can I just do one carb? its the only one with an obvious problem.

[Gordon]

Judging by the picture, you have a leaky float bowl o-ring.  This could be the only problem, or it could be in addition to other problems.  Is there any fuel leaking out of the overflow tube?  Are the overflow tube and standpipe clear and open?  The soot-fouled plug could be caused by an incorrect float level in that carb, or it could be any other number of things.  Best to replace all float bowl o-rings while you have the carbs off the bike, clean out all the jets and passageways, and check the float levels.   

[750goes]

I enlarged your posted picture, and it looks like there is a fair bit of crap also on top of your carburettor above where the float bowl joins the main body of the carb, its also shiny - have you sprayed something on or around this area?

I would ask the question, is your tank leaking and dripping on top of this carburettor, is the petcock leaking as well and running down the fuel line

is the overflow plug cracked as well??? just a few simple checks first.

[TwoTired]

Okay, I'm a lazy mechanic who doesn't want to take anything apart unless it needs it.  From the pic, it sure seems like the float bowl gasket isn't doing the job anymore.  Seems likely that somebody took off the bowl twiddled around inside and put it back on without renewing the seal.

If that is the only carb giving trouble, it's pretty accessible while still on the bike.
Check the bottom drain line to see if it is clear.  It is entirely possible to check the most of the guts of the outer carbs by removing the float bowls.  The bowl comes off with 4 screws and a minimum of personal contortion.  You can then check the bowl for cruddy bits and clean it out. The float height can be checked. And the float valve can be checked for leaks when in the up position.  The bowl gasket can be replaced and all of it can be put back together.  If you can still find carb cleaner with methylene chloride in it, it will remove all the discoloration from the outside of the carbs.  Methylene chloride is also used in paint removers so make a shallow pan for under the carbs if you like the present color of the coating on the engine cases.

The whole thing shouldn't take more than an hour.  And, that will be a LOT faster than removing and cleaning the entire carb bank.
You can then use the time saved to polish other bits of bike or just ride it around.

Anyway, dropping the bowl will give you a good idea of what the carb insides are like.  If it's really disgusting, then you'll know that the whole bank needs cleaning.

Cheers,

[Bob Wessner]

I am trying to leave pulling the carbs off completely until winter..

Can we assume you live in the southern hemisphere someplace??

[Terry in Australia]

Henry's a sheep shagger, er, New Zealander!

[TwoTired]

I forgot to add that carb cleaner with methylene chloride will most definately attack rubber seals.  Do the cleaning before introduction of new seals, or keep such contact very very brief.

Gunk Carb Medic WAS a personal favorite before the environazis had that formula removed from Kalifornia distribution,
 

[Bob Wessner]

environazis

Good one. 

[Henry Dorset Case]

Henry's a sheep shagger, er, New Zealander!

meet my girlfriend, Baaaaaaaaaaabara

[Terry in Australia]

Henry's a sheep shagger, er, New Zealander!

meet my girlfriend, Baaaaaaaaaaabara

Good one Henry, have you received your new Boge shockers yet? Cheers, Terry.

[Sam Green Racing]

Takes one to know one     

[Henry Dorset Case]

Henry's a sheep shagger, er, New Zealander!

meet my girlfriend, Baaaaaaaaaaabara

actually no, and I am just about due to email him.  I cheaped out and got USPS postage (still $30USD!!!) so if they've gone west, I am screwed....    my fault entirely...

I will post if and when they do turn up.

Good one Henry, have you received your new Boge shockers yet? Cheers, Terry.

[dusterdude]

tt,i must say man,you`re looking better these days.

[8 Track]

Definitely the float needle.  The gasket is just a secondary problem.  I bet the gas ran out of that little black tube!  It runs crappy on the bottom end because the gas level is too high and that cylinder is rich.  When you go faster ( ) the gas level comes down to a normal level.  Was your petcock turned off?  Maybe it leaks too.

[scunny]

Nothing wrong with agood looking sheep, didn't we send all the ugly ones to Stralia ?   

[TwoTired]

didn't we send all the ugly ones to Stralia ?   

I thought that's what Britain did in 1788.





Just joking...

[Henry Dorset Case]

Definitely the float needle.  The gasket is just a secondary problem.  I bet the gas ran out of that little black tube!  It runs crappy on the bottom end because the gas level is too high and that cylinder is rich.  When you go faster ( ) the gas level comes down to a normal level.  Was your petcock turned off?  Maybe it leaks too.

this sounds plausible to me.... the only thing the guy who sold me the bike said to me was "always turn the gas off at the petcock when you park the bike".... Id already looked at the OTHER side of the bike and said "I'll take it"  (soooo rational in my bike buying decisions....) pfffft its only money after all

[8 Track]

Turning the gas off is a good practice anyway, since gravity feed systems never stop working!