Topic: gas leak issue(cb650sc-1982)

[rab1dwolf]

new issue with the bike.

I put the thing back together and was about to take it out and I noticed a gas leak. so I removed the vacuum assembly believing that to be the culprit.

The carb#4 was leaking and it looked like from the seal area around the float bowl. So I drained it and took it off.

I had JUST replaced the seals etc in the carbs and now that I've taken the thing apart again the rubber seal on the float bowl does not fit.

It has somehow managed to stretch itself on the back right corner to where it will not fit in the groove so I can't get the bike back together.


So I come here to ask the almighty gurus a few questions:

1) how could this thing have gotten stretched
2) how can I make it fit (should I trim it and glue it back together?)



once again this is a BRAND new seal I put in there.  The bike has only been turned over twice since then.  I'm at a loss as to what to do and quickly running out of semi-decent weather.

[cadler]

I am having the same problem. I think the gaskets expand when exposed to gas, then the get in the way of the float travel not shutting off the gas when the bowl is filled. I am going to get gasket material and cut my own.

[cb650]

If it isnt stretched out to much permatex makes a sealer that works with gas. It is very sticky. Forgot the name starts with a H bought it at checker.



                   Terry

[dusterdude]

hylomar?

[Gordon]

I am having the same problem. I think the gaskets expand when exposed to gas, then the get in the way of the float travel not shutting off the gas when the bowl is filled. I am going to get gasket material and cut my own.

Cadler,
I'm still somewhat confused about your particular situation.  The float bowl o-ring sits inside a groove in the top of the float bowl, so even once it comes in contact with the fuel and expands, it should only be forming a tighter seal within that groove rather than interfering with the movement of the floats.  If it's set completely in place in the groove, and the float bowl is tightened down properly, there should be nowhere else for the o-ring to go.

The only way I can think of that the o-ring could interfere with anything inside the float chamber is if it had slipped out of place before tightening and was no longer inside it's groove.  Is that what's happening?

[Gordon]

rab1dwolf,
Check out this thread.

http://www.sohc4.us/forums/index.php?topic=7480.0

Cadler, I just noticed you already pretty much answered my question in that other thread, but I'm still unsure about one thing.  How is it the o-ring is getting out of the groove once the float bowl is in place and tight?

[rab1dwolf]

gordon thanks for the link.

That thread actually discusses the one I have.  I bought them from siruis consolidated:)

I've had it sitting all night so I'll check it today and see what I get.

[cadler]

The float bowl gasket fits nice and tight in the groove. When the float bowls fill with gas, the gaskets  for some unknown reason expand into the float bowl chamber.
Are we talking about the same thing ? floatbowl O ring = float bowl gasket

[Gordon]

The float bowl gasket fits nice and tight in the groove. When the float bowls fill with gas, the gaskets  for some unknown reason expand into the float bowl chamber.
Are we talking about the same thing ? floatbowl O ring = float bowl gasket

I'm pretty sure we're talking about the same thing, an o-ring is just a specific type of gasket.
Forgive all my questions, I just really want to help you get to the bottom of this. 

Other than the fact that your float bowls are overflowing with the new o-rings in place and the fuel turned on, how can you tell it's the o-ring causing the problem?  The reason I'm asking is because there are several other things that could cause the fuel to overflow, and there's really no way of seeing what's going on inside the float chambers once the bowl is in place. 

I also don't understand how the o-ring, once firmly in place in the groove and the float bowl tightened securely against the carb body, could expand out into the float chamber.  Is there something different about the 650 carb bowls where there would be room for the o-ring to sqeeze out of?  I've worked on all the other sohc4 carbs, but never the 650. 

[rab1dwolf]

Well after letting it sit out in my kitchen all day it has returned to normal size.  I'm gonna let it sit another day just in case.

The gasket/oring whatever you want to call it does sit in a groove and it shouldn't expand into the bowl because of the design.  but theres no denying that when I took it off it was almost a half inch LONGER then it was supposed to be.

Originally I thought my leak was from tha vacuum assembly above the carb so I took that off.  It also let me get a better view of what was going on.

as for inside the bowl: the float seems to operate fine.  I had also checked the floats for cracks/defects before reassemble and they all looked fine.  I did replace that little float valve with new ones but it seems to be working fine as well. overall the internals seem to be functioning but for some reason I am getting that #4 over filled...I'm hoping that reseating the gasket and making sure those screws are in nice and tight will solve it.


think maybe I should replace the screws as well? They are the origina ones and the threads look ok but they are discolored/rusty.

[cb650]

Dusterdude is correct.   I dont even know where my tube of it is anymore.  Worked good.



                                Terry

[rab1dwolf]

update:

put the bowl and gasjet back on and tightened the screws down as tight as they go.  Turned the fuel on hit the starter....


and I got a miniture niagra falls.

The leaks worse now then before.

Going to disassemble again tomorrow and take the float and everything out and see if I can figure this thing out.


Its sad I only have a half a tank of gas left and I still havent ridden it:(

[rab1dwolf]

update #2: well i went out today to work on the bike.
i took a rubber mallet andgave it a good thump to see if it would dislodge the float (if it was the problem)
still was leaking so what I did was kept the bike running when I first saw signs of it leaking again and turned the gas line off and wiped the gas before it became an issue.  After doingthisonce or twice I then tried it on "RES" since I saw a post on here about someone that had a leak that only happened in the on position.

low and behold. no leak.  so I switched it over to on and now its running fine without an leaks.  Kinda strange it seems to fixed itself.

new issue however: I have to leave the choke on otherwise the rpms taper of and it dies.
Also there is what sounds kind of like a back fire but its kind of a "pinging" sound that occasionally sounds but I can't place it quite yet.  The sound only comes when idle.

I'm recharging the battery now since I seem to have killed it yet again in my monkeying around today:)

any advice on the rpm issue and/or the weird noise please let me know

[Bob Wessner]

I don't see how the source of the fuel (reserve vs. on) at the tank end could affect a leak at the carbs. I think you still have a problem, it's just an intermittent one.

[rab1dwolf]

yeah it didnt make any sense to me.

I think the problem fixed itself.

I've got bigger issues now though.  Found out 3 of the 4 exhaust pipes have holes right where the muffler connects.  I got some patch stuff and am fixing that.

However my clutch doesn't seem to do jack when I depress the handgrip. I even have a new cable on there.  Hopefully tomorrow I can solve that mystery

[cadler]

the reason I know it is the gaskets is because when I drop the float bowl you can see how much the gasket has expanded. After it dries it shrinks back down to normal size.
I let it shrrink down and re installed it. It seems to be working ok for now.
Craig
Sorry for the late post.

[byidesign]

Do be careful on something that happened to me, if you have used carb cleaner, or
  some additives, even too much ethanol in the fuel, will make the O rings and gaskets swell
    up.  try an old one in a cup of fuel for awhile to test it out.