« previous next »
Pages: [1]   Go Down

Author Topic: 74 C550 Carb Float Bowl Round O-Ring Gasket ID Size?  (Read 1468 times)

0 Members and 1 Guest are viewing this topic.

Offline uncle_fester

  • Full Member
  • *
  • Posts: 51
74 C550 Carb Float Bowl Round O-Ring Gasket ID Size?
« on: May 29, 2018, 06:58:54 PM »
I've been fighting a slow fuel leak on my #2 carb of my '74 CB550. Today, I drilled and re-tapped for M5 screws. Everything is super clean and tight with new "house" shaped gaskets from 4into1, but I'm still getting a slow drip of fuel from the bowl.

Does anyone know the o-ring ID size that would fit the carb bowl for this model? I want to try a larger diameter option.
Logged

Offline flybox1

  • My wife thinks I'm a
  • Really Old Timer ...
  • *******
  • Posts: 14,289
Re: 74 C550 Carb Float Bowl Round O-Ring Gasket ID Size?
« Reply #1 on: May 30, 2018, 09:08:57 AM »
Are you sure the leak is not coming from higher up on the carb?  How good are the fuel line/connections between the carbs?  If you are getting fuel leaking past the bowl o-rings, you have a bigger problem...like incorrect float/fuel level.

As far as the bowl o-rings, the pre-shaped viton ones should work just fine.
Logged
'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

Past Bikes
1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
77/78 cool 2 member #3
"Knowledge without mileage equals bullsh!t" - Henry Rollins

"This is my CB. There are many like it, but this one is mine…"

Offline Bankerdanny

  • Eventually I will be old enough in reality to be
  • Really Old Timer ...
  • *******
  • Posts: 7,623
  • Endeavor to persevere
Re: 74 C550 Carb Float Bowl Round O-Ring Gasket ID Size?
« Reply #2 on: May 30, 2018, 11:13:27 AM »
The fuel shouldn't reach the top of the bowl. If it does there is something wrong with your float settings. That said, the fuel in the bowl is only under gravity pressure and when the bowl is full, not under any pressure at all. There is no reason for the bowls to leak where they meet the carb body.

What makes you believe that is the source of the leak?
Logged
"The problem with quotes on the Internet is that you never know if they're true" - Abraham Lincoln

Current: '76 CB750F. Previous:  '75 CB550F, 2007 Yamaha Vino 125 Scooter, '75 Harley FXE Superglide, '77 GL1000, '77 CB550k, '68 Suzuki K10 80, '68 Yamaha YR2, '69 BMW R69S, '71 Honda SL175, '02 Royal Enfield Bullet 500, '89 Yamaha FJ1200

Offline uncle_fester

  • Full Member
  • *
  • Posts: 51
Re: 74 C550 Carb Float Bowl Round O-Ring Gasket ID Size?
« Reply #3 on: May 30, 2018, 03:58:27 PM »
It's a slow leak, but I'd prefer no leaks. It's actually on #3, not #2. Here's a photo with it on the side kick stand.

First image is from the right side. Second image is from the left side.

Logged

Offline uncle_fester

  • Full Member
  • *
  • Posts: 51
Re: 74 C550 Carb Float Bowl Round O-Ring Gasket ID Size?
« Reply #4 on: May 30, 2018, 04:00:07 PM »
Quote from: flybox1 on May 30, 2018, 09:08:57 AM
Are you sure the leak is not coming from higher up on the carb?

I'm using 1/4" PVC tubing between the carbs. It's pretty new. Haven't looked closely at that yet. Could be the culprit.
« Last Edit: May 30, 2018, 04:04:34 PM by uncle_fester »
Logged

Offline Little_Phil

  • Hot Shot
  • ***
  • Posts: 680
Re: 74 C550 Carb Float Bowl Round O-Ring Gasket ID Size?
« Reply #5 on: May 31, 2018, 01:04:53 AM »
I made this list of O rings from info from others on this site:
Float bowl: 68mm x 2mm
Main jet:  3.5mm x 1.2mm
Float valve seat:  5mm x 1.5mm
Fuel Tee:  7mm x 2mm
Drain screw: think I went with 4mm x 2mm after finding a few different sizes mentioned.
They didn't all appear to be exactly as original, but are doing the job. My supplier supplied Viton 75.
Having said that it's unusual to leak at the join. Think originally there was also some sort of glue/sealant there, but may have been just to keep seal in place. Are the faces distorted by clamping unevenly with oversize screws? Check with straight edge.
Logged

Offline flybox1

  • My wife thinks I'm a
  • Really Old Timer ...
  • *******
  • Posts: 14,289
Re: 74 C550 Carb Float Bowl Round O-Ring Gasket ID Size?
« Reply #6 on: June 01, 2018, 06:48:55 AM »
Quote from: uncle_fester on May 30, 2018, 04:00:07 PM

I'm using 1/4" PVC tubing between the carbs. It's pretty new. Haven't looked closely at that yet. Could be the culprit.
Huh?  :-\

Between 1/2 and 3/4 carbs should be T-connectors with double o-rings on each side ...

Logged
'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

Past Bikes
1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
77/78 cool 2 member #3
"Knowledge without mileage equals bullsh!t" - Henry Rollins

"This is my CB. There are many like it, but this one is mine…"

Offline Jooky

  • Full Member
  • *
  • Posts: 50
Re: 74 C550 Carb Float Bowl Round O-Ring Gasket ID Size?
« Reply #7 on: June 01, 2018, 08:02:54 AM »
As stated by others above, check the connections between carbs. I had the exact same problem after fueling my bike up after it sat for a long time. It appeared that there was a leak coming from the screws that attach the float bowls to the carb bodies, but it was actually originating from the piping/o-rings connecting the carbs above.
Logged

Offline uncle_fester

  • Full Member
  • *
  • Posts: 51
Re: 74 C550 Carb Float Bowl Round O-Ring Gasket ID Size?
« Reply #8 on: June 01, 2018, 08:42:52 AM »
Quote from: Jooky on June 01, 2018, 08:02:54 AM
As stated by others above, check the connections between carbs. I had the exact same problem after fueling my bike up after it sat for a long time. It appeared that there was a leak coming from the screws that attach the float bowls to the carb bodies, but it was actually originating from the piping/o-rings connecting the carbs above.

Thanks. I'll do some investigating before taking the bowls off again.
Logged

Offline bryanj

  • Really Old Timer ...
  • *******
  • Posts: 15,032
  • CB500 Number 1000036
Re: 74 C550 Carb Float Bowl Round O-Ring Gasket ID Size?
« Reply #9 on: June 01, 2018, 11:05:40 AM »
If it is dripping out of the brass nipple on the bottom the internal standpipe can crack and cause it
Logged
Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

Remember "Its always in the last place you look" COURSE IT IS YOU STOP LOOKIN THEN!

Offline uncle_fester

  • Full Member
  • *
  • Posts: 51
Re: 74 C550 Carb Float Bowl Round O-Ring Gasket ID Size?
« Reply #10 on: June 03, 2018, 08:37:29 AM »
After looking at it closer, I think it's coming from the fuel line where it attaches to the barb between the carbs. I'm using 1/4" ID PVC tubing and the clamps I have are a little big for the hose. I had to make an order with 4into1, and am going to try the 5.5mm genuine fuel line that will work well for the hose barb and the clamps I have.
Logged

Offline bryanj

  • Really Old Timer ...
  • *******
  • Posts: 15,032
  • CB500 Number 1000036
Re: 74 C550 Carb Float Bowl Round O-Ring Gasket ID Size?
« Reply #11 on: June 03, 2018, 03:28:53 PM »
PVC will not stand the ethanol in the fuel and go hard and leak, you need the proper 5.5mm rubber which is a swine to get onto the Tee pieces but is the only type that works properly
Logged
Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

Remember "Its always in the last place you look" COURSE IT IS YOU STOP LOOKIN THEN!
Pages: [1]   Go Up
« previous next »