Severe fuel leak from somewhere behind and below #1&3 carbs?

[F6Ghostrider VRCC #32501]

Greetings folks. A little background. 98 Tourer, 226,909 miles. Never had to touch carbs. Bike sat about five weeks recently. On the way to work one morning I started smelling fuel. On getting to work my leathers were saturated with gasoline. Today, I rolled her out to wash and further investigate the reason fuel was leaking. Upon starting, I noticed on the right side, behind the left and center carbs, gasoline was pouring out. It flooded the intake manifold. My question is, could it be the fuel rail, O-rings or a stuck float? It was leaking so bad I couldn’t tell exactly where it was coming from.
I know that’s not a lot of information, but I’m not trying to make this post to lengthy.
I checked the search board and the only thing I could see was something related to the fuel rail O-rings. Any and all help is appreciated. Not looking forward to pulling the carbs, but I will if I have to.
Thank you in advance to those who know and are willing to provide information to help me resolve this issue.
Thank you, Jeff.

[Chrisj CMA]

Most likely fuel rails. I’m getting ready to do mine too. Not leaking but it’s time

[Challenger]

I'm with Chris on this one. If it was a stuck float, fuel should run out the overflow tubes and drip out the bottom by the drool hose.
Wow, only got 227,000 out of those seals huh? 

[98valk]

Greetings folks. A little background. 98 Tourer, 226,909 miles. Never had to touch carbs. Bike sat about five weeks recently. On the way to work one morning I started smelling fuel. On getting to work my leathers were saturated with gasoline. Today, I rolled her out to wash and further investigate the reason fuel was leaking. Upon starting, I noticed on the right side, behind the left and center carbs, gasoline was pouring out. It flooded the intake manifold. My question is, could it be the fuel rail, O-rings or a stuck float? It was leaking so bad I couldn’t tell exactly where it was coming from.
I know that’s not a lot of information, but I’m not trying to make this post to lengthy.
I checked the search board and the only thing I could see was something related to the fuel rail O-rings. Any and all help is appreciated. Not looking forward to pulling the carbs, but I will if I have to.
Thank you in advance to those who know and are willing to provide information to help me resolve this issue.
Thank you, Jeff.

tighten the end nuts of the thru bolts that hold the carb banks together. they get loose. then let it sit for a day. usually zero leaks after that.

[98valk]

Most likely fuel rails. I’m getting ready to do mine too. Not leaking but it’s time

what time?  once o-rings installed do not have a life span unless they are subjected to events for which they are not designed for.   for OEM higher grade buna-n o-rings that would be the wrong fuel additives and high operating heat over 250 degrees F.

if u have viton installed they are rated at an even higher temp.

[F6Ghostrider VRCC #32501]

Are the end nuts on the though bolts easily accessible without removing all the chrome?

[98valk]

Are the end nuts on the though bolts easily accessible without removing all the chrome?

see nuts #31, thru bolts are #9.  usually only a 1/16 of a turn is needed.
although last time I did mine one nut needed 1/8 of a turn.  over 500 miles later still zero leaks.

https://www.partzilla.com/catalog/honda/motorcycle/2000/gl1500c-a-valkyrie/carburetor-assy

[F6Ghostrider VRCC #32501]

Chris! Thank you, thank you, and thank you a thousand times over. I understand the concept of what tightening the nuts would do, but I admit I was a little skeptical of the success of that procedure. I followed your instructions and it worked like a champ!
I was ready to pull the cabs and send them off for rebuild considering the miles on my Dragon.
Soooooo happy. Thanks again Buddy!  

[HayHauler]

Chris! Thank you, thank you, and thank you a thousand times over. I understand the concept of what tightening the nuts would do, but I admit I was a little skeptical of the success of that procedure. I followed your instructions and it worked like a champ!
I was ready to pull the cabs and send them off for rebuild considering the miles on my Dragon.
Soooooo happy. Thanks again Buddy!  

Hay 
Jimmyt

[F6Ghostrider VRCC #32501]

My apologies. I did not read through all the posts carefully enough and overlooked 98valk, who provided good advice about stopping a fuel leak from the right-side bank of carbs. Thank you, 98valk!

Thanks for the advice about tightening the nuts on the carburetor thru-bolts. That worked like a charm. The two front, interior nuts were difficult to reach as I do not own a long 10mm box wrench. I followed your instructions to the letter, and it worked like a champ!

That's what I love about this forum. So much experience and knowledge out there.

Best regards to all who read and participate in this forum,

Jeff.  

[Joe333x]

My apologies. I did not read through all the posts carefully enough and overlooked 98valk, who provided good advice about stopping a fuel leak from the right-side bank of carbs. Thank you, 98valk!

Thanks for the advice about tightening the nuts on the carburetor thru-bolts. That worked like a charm. The two front, interior nuts were difficult to reach as I do not own a long 10mm box wrench. I followed your instructions to the letter, and it worked like a champ!

That's what I love about this forum. So much experience and knowledge out there.

Best regards to all who read and participate in this forum,

Jeff.  

I would order new O-Rings, it may have stopped or slowed it for now but that's just because you are jamming the metal in tighter. The o rings dry and get flat and brittle over 20+ years of ethanol fuel exposure. As long as the fuel rail o ring is in its place on the carb and the o ring is bigger than the fuel rail, it wont leak.

[98valk]

My apologies. I did not read through all the posts carefully enough and overlooked 98valk, who provided good advice about stopping a fuel leak from the right-side bank of carbs. Thank you, 98valk!

Thanks for the advice about tightening the nuts on the carburetor thru-bolts. That worked like a charm. The two front, interior nuts were difficult to reach as I do not own a long 10mm box wrench. I followed your instructions to the letter, and it worked like a champ!

That's what I love about this forum. So much experience and knowledge out there.

Best regards to all who read and participate in this forum,

Jeff.  

I would order new O-Rings, it may have stopped or slowed it for now but that's just because you are jamming the metal in tighter. The o rings dry and get flat and brittle over 20+ years of ethanol fuel exposure. As long as the fuel rail o ring is in its place on the carb and the o ring is bigger than the fuel rail, it wont leak.

""brittle over 20+ years of ethanol fuel exposure. "" 

 not true at all.  buna-n is designed for at least 15% ethanol, it doesn't affect the o-rings.  plus Honda uses a higher grade of buna-n. 
using wrong fuel additives will degrade buna-n. temperatures over 250F will degrade it.

where is your study documenting buna-n o-rings get brittle at 20 yrs?? 
I have not found an engineering manufacture that will state what u just did.

[Challenger]

Scientific study or not, the fuel rail packing I've replaced were cracked or even crumbling. Doesn't matter why, they needed replaced. Sometimes $hit just happens.

[98valk]

Scientific study or not, the fuel rail packing I've replaced were cracked or even crumbling. Doesn't matter why, they needed replaced. Sometimes $hit just happens.

it does matter why they needed to be replaced, cause and effect.
buna-n aka nitrile does not like solvents that are in many aftermarket fuel additives.  Honda rates their o-rings for 10% ethanol fuel.

https://www.marcorubber.com/o-ring-material-selection-comparison.htm

[Joe333x]

Scientific study or not, the fuel rail packing I've replaced were cracked or even crumbling. Doesn't matter why, they needed replaced. Sometimes $hit just happens.

Yeah theres only one member on this board that continues to give terrible advice about these 20+ year old o rings. I rebuilt all six of my carbs and replaced every o ring after they started leaking soon after I purchased my bike last year. Last thing I want to fool around with is gas leaking. Most if not all the o rings were flat, dry and broke easily. Even tires have an expiration date, they get dry rot and crack because rubber does not last forever, then you add ethanol to the mix. I cation anyone with a fuel leak to not take poor advice and try cheap fixes, if you're leaking fuel, rebuild your carbs and replace the o rings. I posted videos on youtube for anyone that wants to do it themselves. I understand the want to try and save time and money with cheap fixes but once you start leaking the o rings will not repair them selves no matter what magic you try, just replace them and you'll be good for another 20+ years.
https://youtu.be/tx3AnNUVahI
https://youtu.be/qiY2pCfTwMw

[98valk]

Scientific study or not, the fuel rail packing I've replaced were cracked or even crumbling. Doesn't matter why, they needed replaced. Sometimes $hit just happens.

Yeah theres only one member on this board that continues to give terrible advice about these 20+ year old o rings. I rebuilt all six of my carbs and replaced every o ring after they started leaking soon after I purchased my bike last year. Last thing I want to fool around with is gas leaking. Most if not all the o rings were flat, dry and broke easily. Even tires have an expiration date, they get dry rot and crack because rubber does not last forever, then you add ethanol to the mix. I cation anyone with a fuel leak to not take poor advice and try cheap fixes, if you're leaking fuel, rebuild your carbs and replace the o rings. I posted videos on youtube for anyone that wants to do it themselves. I understand the want to try and save time and money with cheap fixes but once you start leaking the o rings will not repair them selves no matter what magic you try, just replace them and you'll be good for another 20+ years.
https://youtu.be/tx3AnNUVahI
https://youtu.be/qiY2pCfTwMw

sorry but u and others spread incorrect info that there is a life span of installed buna-n o-rings and that ethanol degrades them.  all false info.   the fuel additives people use like seafoam slowly degrades them. Honda BUNA-N is designed for 10% ethanol. Ethanol DOES NOT degrade them. I post engineering facts about buna-n and not my opinions. There isn't a life span for any installed o-rings unless they are subjected to conditions that are known to degrade them, for buna-n 10% Ethanol is not one of them.

my scoot never used seafoam or B12 except maybe one time, when I first brought it and then did some research, owned it since new for 24 yrs now zero leaks except when the carb thru bolts loosened up. tightened them, then zero leaks for 10s of thousands of miles. 
 many many over the yrs on here have stated they use seafoam, B12, Lucas every tank and then many many have to have their carbs rebuilt.
The OP message me and stated the nuts of the thru bolts were loose, he tightened them and now it doesn't leak.  He also stated he has over 200k miles on his scoot and first time the carbs ever leaked.
Enjoy.

[rug_burn]

No, 98valk, o-rings do not last forever, let's put that fairy tale to bed. 

They get cooked by heat, the plasticizer leeches out of the rubber, and ozone has its way with them.  Also shemicals in the fuel

Just take off an intake tube off your 98 Valk, now 26 years old and the o-ring, and even moreso the nitrile seal sleeve at the top, will be some rock-hard ceramic-like material where once they were rubber.

Nitrile o-rings only have a 15 year shelf life  (from the Parker Hannifin Corp), and I believe it's 10 years for aviation applications.

Parker recommends a Viton compound (V0834-70) for gasoline with 5%-20% alcohol, BTW, not nitrile.                                                                                                                                                                                                                                                                                                                                                                           
 
Nothing lasts forever, Grasshopper...  (sad)
 

[Joe333x]

Scientific study or not, the fuel rail packing I've replaced were cracked or even crumbling. Doesn't matter why, they needed replaced. Sometimes $hit just happens.

Yeah theres only one member on this board that continues to give terrible advice about these 20+ year old o rings. I rebuilt all six of my carbs and replaced every o ring after they started leaking soon after I purchased my bike last year. Last thing I want to fool around with is gas leaking. Most if not all the o rings were flat, dry and broke easily. Even tires have an expiration date, they get dry rot and crack because rubber does not last forever, then you add ethanol to the mix. I cation anyone with a fuel leak to not take poor advice and try cheap fixes, if you're leaking fuel, rebuild your carbs and replace the o rings. I posted videos on youtube for anyone that wants to do it themselves. I understand the want to try and save time and money with cheap fixes but once you start leaking the o rings will not repair them selves no matter what magic you try, just replace them and you'll be good for another 20+ years.
https://youtu.be/tx3AnNUVahI
https://youtu.be/qiY2pCfTwMw

sorry but u and others spread incorrect info that there is a life span of installed buna-n o-rings and that ethanol degrades them.  all false info.   the fuel additives people use like seafoam slowly degrades them. Honda BUNA-N is designed for 10% ethanol. Ethanol DOES NOT degrade them. I post engineering facts about buna-n and not my opinions. There isn't a life span for any installed o-rings unless they are subjected to conditions that are known to degrade them, for buna-n 10% Ethanol is not one of them.

my scoot never used seafoam or B12 except maybe one time, when I first brought it and then did some research, owned it since new for 24 yrs now zero leaks except when the carb thru bolts loosened up. tightened them, then zero leaks for 10s of thousands of miles. 
 many many over the yrs on here have stated they use seafoam, B12, Lucas every tank and then many many have to have their carbs rebuilt.
The OP message me and stated the nuts of the thru bolts were loose, he tightened them and now it doesn't leak.  He also stated he has over 200k miles on his scoot and first time the carbs ever leaked.
Enjoy.

Mileage has nothing to do with it, actually the higher the mileage the less of concern because fuel wasn't sitting long in the carbs as a lower mileage bike. You're on an island though with thinking tightening the bolts is a real fix. It's just a bandaid. If you think about it this way if you take a pipe and put it in a tube and the pipe has a rubber ring around it that stops anything from getting through it doesn't matter how far it is in the tube as long as the rubber ring is around it and in so unless the fuel rail o-ring is sticking out of the hole it goes in then it shouldn't be leaking the tube on the carb that the fuel rail goes into is not tapered.

[98valk]

No, 98valk, o-rings do not last forever, let's put that fairy tale to bed. 

They get cooked by heat, the plasticizer leeches out of the rubber, and ozone has its way with them.  Also shemicals in the fuel

Just take off an intake tube off your 98 Valk, now 26 years old and the o-ring, and even moreso the nitrile seal sleeve at the top, will be some rock-hard ceramic-like material where once they were rubber.

Nitrile o-rings only have a 15 year shelf life  (from the Parker Hannifin Corp), and I believe it's 10 years for aviation applications.

Parker recommends a Viton compound (V0834-70) for gasoline with 5%-20% alcohol, BTW, not nitrile.                                                                                                                                                                                                                                                                                                                                                                           
 
Nothing lasts forever, Grasshopper...  (sad)
 

not a fairy tale. O-Rings, pipe gaskets, etc., do last forever if they are not subjected to conditions for which they are not designed for.
 buna-n o-rings are rated to consistent 257F operating temp. I never looked up the highest intermittent temp they can operate at.
Who's valkyrie is running at that temp TO HEAT COOK THE O-RINGs??

The o-rings are installed inside of the carbs and are not exposed to ozone and sunlight.

Buna-n is designed for the ethanol fuel and the other chemicals in it. Anybody can read that on various buna-n material compatible websites.

 viton has the higher temp and higher ethanol % over buna-n. I read before buna-n is good up to 15%
""Buna o-rings:
    Excellent resistance to petroleum-based oils and fuels, silicone greases, hydraulic fluids, water and alcohols
    Low compression set
    High tensile strength
    Abrasion resistance
    Superior performance in ethanol/methanol blended gasoline

Viton® o-rings:

    High temperature resistance
    Outstanding chemical resistance
    Low compression set
    Ozone resistant
    Low outgassing""
https://www.applerubber.com/blog/how-to-make-the-right-choice-between-viton-and-buna-o-rings/
Again! and Again!, Shelf life HAS ZERO TO DO WITH OPERATIONAL/SERVICE LIFE! PERIOD!!

SERVICE LIFE IS ALWAYS DETERMINED BY THE CONTROLLED OPERATIONAL ENVIRONMENT OF THE INSTALLED O-RINGS! ASK ANY MAINTENANCE ENGINEER, THEY WILL SAY THE SAME. A SERVICE LIFE IS DETERMINED BY CONTROLLED TESTING OF THE O-RING IN OPERATION. PERIOD!!

[Challenger]

Give it a rest. Many people have had to replace fuel rail o- rings due to being cracked and brittle. Obviously not for ever. Most of us have no idea what the previous owners of  20 to 25 year old bikes have put in their fuel tanks or how long they have set and it doesn't matter because we still had to replace them . Ricky-D used to rag on about bearings are for ever also, yet many have had left rear brgs disintegrate . We replace  damaged or worn part and ride on.
No disrespect intended,

[Joe333x]

Give it a rest. Many people have had to replace fuel rail o- rings due to being cracked and brittle. Obviously not for ever. Most of us have no idea what the previous owners of  20 to 25 year old bikes have put in their fuel tanks or how long they have set and it doesn't matter because we still had to replace them . Ricky-D used to rag on about bearings are for ever also, yet many have had left rear brgs disintegrate . We replace  damaged or worn part and ride on.
No disrespect intended,

One of two things will happen, his fuel rail which obviously needed new o rings already since he tightened the bolts will start leaking again and he will replace them and see what 20+ year old fuel rail o rings look like or he will tighten so bolts so hard trying stop the leak that he will break something. Guy has been quoting stuff about o rings lasting forever for years, thankfully there are great people out there like the guys at https://www.valkyrieflatsix.com/ those guys provide tons of information on the Valkyrie fb group David helped me with tons of info and parts to help me do my carb rebuild. I now have dual fuel filters, a manual petcock and electric fuel shut off. Bike runs like a champ and doesnt leak anymore. Tuned it with a colortune and digisync after the rebuild too.

[Mooskee]

I rebuild 25 carb sets per year, give or take a couple. The vast majority have dried out, brittle, cracked O-rings. You can claim that the O-rings will last forever under the right conditions. Apparently the 25 sets I see each year have not been under said conditions. I also find bad bearings on the crossover arms so often that I now replace them on every build. In fact I replace 169 parts.
I do this to provide reliable operation to the fellow riders that trust me to rebuild their carbs. It has been insinuated that those of us providing this service are somehow fear mongering the customers into carb rebuilds. I frankly find that offensive. I go out of my way to answer questions and help resolve the problem. If rebuilding is the solution,I can do that and make them like new. Maybe tightening up the nuts fixes the problem. Great for you. If not, l can definitely help. In fact I have a test engine, and will balance and tune them to run on your bike.
Enough said I guess. I'm just sick and tired of the O-ring argument, and the bashing of professional carb rebuilding.

[Joe333x]

I rebuild 25 carb sets per year, give or take a couple. The vast majority have dried out, brittle, cracked O-rings. You can claim that the O-rings will last forever under the right conditions. Apparently the 25 sets I see each year have not been under said conditions. I also find bad bearings on the crossover arms so often that I now replace them on every build. In fact I replace 169 parts.
I do this to provide reliable operation to the fellow riders that trust me to rebuild their carbs. It has been insinuated that those of us providing this service are somehow fear mongering the customers into carb rebuilds. I frankly find that offensive. I go out of my way to answer questions and help resolve the problem. If rebuilding is the solution,I can do that and make them like new. Maybe tightening up the nuts fixes the problem. Great for you. If not, l can definitely help. In fact I have a test engine, and will balance and tune them to run on your bike.
Enough said I guess. I'm just sick and tired of the O-ring argument, and the bashing of professional carb rebuilding.

Honestly i don't think it's anyone bashing the rebuild guys besides the one guy that chimes in every thread and tells guys to tighten the nuts. My experience is just as you described, the guys that rebuild carbs professionally are not in it to make a fortune and definitely provide great free advice for folks looking to do it themselves.

[98valk]

Scientific study or not, the fuel rail packing I've replaced were cracked or even crumbling. Doesn't matter why, they needed replaced. Sometimes $hit just happens.

Yeah theres only one member on this board that continues to give terrible advice about these 20+ year old o rings. I rebuilt all six of my carbs and replaced every o ring after they started leaking soon after I purchased my bike last year. Last thing I want to fool around with is gas leaking. Most if not all the o rings were flat, dry and broke easily. Even tires have an expiration date, they get dry rot and crack because rubber does not last forever, then you add ethanol to the mix. I cation anyone with a fuel leak to not take poor advice and try cheap fixes, if you're leaking fuel, rebuild your carbs and replace the o rings. I posted videos on youtube for anyone that wants to do it themselves. I understand the want to try and save time and money with cheap fixes but once you start leaking the o rings will not repair them selves no matter what magic you try, just replace them and you'll be good for another 20+ years.
https://youtu.be/tx3AnNUVahI
https://youtu.be/qiY2pCfTwMw

sorry but u and others spread incorrect info that there is a life span of installed buna-n o-rings and that ethanol degrades them.  all false info.   the fuel additives people use like seafoam slowly degrades them. Honda BUNA-N is designed for 10% ethanol. Ethanol DOES NOT degrade them. I post engineering facts about buna-n and not my opinions. There isn't a life span for any installed o-rings unless they are subjected to conditions that are known to degrade them, for buna-n 10% Ethanol is not one of them.

my scoot never used seafoam or B12 except maybe one time, when I first brought it and then did some research, owned it since new for 24 yrs now zero leaks except when the carb thru bolts loosened up. tightened them, then zero leaks for 10s of thousands of miles. 
 many many over the yrs on here have stated they use seafoam, B12, Lucas every tank and then many many have to have their carbs rebuilt.
The OP message me and stated the nuts of the thru bolts were loose, he tightened them and now it doesn't leak.  He also stated he has over 200k miles on his scoot and first time the carbs ever leaked.
Enjoy.

Mileage has nothing to do with it, actually the higher the mileage the less of concern because fuel wasn't sitting long in the carbs as a lower mileage bike. You're on an island though with thinking tightening the bolts is a real fix. It's just a bandaid. If you think about it this way if you take a pipe and put it in a tube and the pipe has a rubber ring around it that stops anything from getting through it doesn't matter how far it is in the tube as long as the rubber ring is around it and in so unless the fuel rail o-ring is sticking out of the hole it goes in then it shouldn't be leaking the tube on the carb that the fuel rail goes into is not tapered.

the o-ring is acting as a gasket btwn to flat surfaces. so as any gasket it is only as good as the bolts holding the joint together so the gasket can seal.

[Timbo1]

the o-ring is acting as a gasket btwn to flat surfaces. so as any gasket it is only as good as the bolts holding the joint together so the gasket can seal.

The fuel rail o-rings fit on the diameter of the fuel tubes and slide into the opening of the carb body.  The seal is formed between the fuel rail and carb body by the fitment of the o-ring on the OD of the fuel tube and the ID of the carb body fuel inlet.  Tightening the carb bank bolts may deform the ends of the fuel tubes enough to apply some force to the o-rings and squish them out of their pocket in a lateral direction to seal against the ID of the carb body inlet but that's not a great solution.  With good o-rings they would seal without the bank bolts that hold the carbs together.

[Joe333x]

the o-ring is acting as a gasket btwn to flat surfaces. so as any gasket it is only as good as the bolts holding the joint together so the gasket can seal.

The fuel rail o-rings fit on the diameter of the fuel tubes and slide into the opening of the carb body.  The seal is formed between the fuel rail and carb body by the fitment of the o-ring on the OD of the fuel tube and the ID of the carb body fuel inlet.  Tightening the carb bank bolts may deform the ends of the fuel tubes enough to apply some force to the o-rings and squish them out of their pocket in a lateral direction to seal against the ID of the carb body inlet but that's not a great solution.  With good o-rings they would seal without the bank bolts that hold the carbs together.

Thanks for explaining that even better than I was trying to. Guy thinks the bolts through the racks hold the o rings in place. If hes ever taken a rack of carbs apart he'd know how difficult the carbs can be to separate so those fuel rails are not getting loose, as long as the o ring is physically in the carb it will not leak unless the o ring is shot. I feel bad for who ever ends up eventually having to rebuild his carbs, going to be a pain to separate them after he has tightened them to try and fix leaks.

[98valk]

the o-ring is acting as a gasket btwn to flat surfaces. so as any gasket it is only as good as the bolts holding the joint together so the gasket can seal.

The fuel rail o-rings fit on the diameter of the fuel tubes and slide into the opening of the carb body.  The seal is formed between the fuel rail and carb body by the fitment of the o-ring on the OD of the fuel tube and the ID of the carb body fuel inlet.  Tightening the carb bank bolts may deform the ends of the fuel tubes enough to apply some force to the o-rings and squish them out of their pocket in a lateral direction to seal against the ID of the carb body inlet but that's not a great solution.  With good o-rings they would seal without the bank bolts that hold the carbs together.

Thanks for explaining that even better than I was trying to. Guy thinks the bolts through the racks hold the o rings in place. If hes ever taken a rack of carbs apart he'd know how difficult the carbs can be to separate so those fuel rails are not getting loose, as long as the o ring is physically in the carb it will not leak unless the o ring is shot. I feel bad for who ever ends up eventually having to rebuild his carbs, going to be a pain to separate them after he has tightened them to try and fix leaks.

it seems Honda thinks the thru bolts hold the carbs together. must be very important if Honda provides a torque number.
service manual
pg 5-17
lnstall the four carburetor joint bolts.
lnstall the rear stay plate and four nuts, and tighten the nuts.
TORQUE: 70 N-m (1.0 kgf-m, 7 Ibf-ft)

it seems Honda thinks nuts get loose.
pg 3-3
maintenance schedule
inspect nuts, bolts, fasteners  every 8k miles.

[rug_burn]

I know-  he never gets tired of for repeating that stuff about the rack clamp bolts.  And it's not even right.  But who wants to argue?
   When configured as in the fuel rails, o-rings seal on cylindrical surfaces, inner and outer,  the o-ring OD and ID compressed between them in a 20% squeeze.   The cross sectional diameter of the o-ring needs to be compressed to 80% of it's original size,  a 20% squeeze.  Like for example a -121 o-ring has  a .103" cross section, so 80% of this is .082, the distance between inner and outer diametrers. 
   You  can also arrange an o-ring as a face seal, with a circular groove in one flat surface sealing to a flat surface on another, like on the intake tube to head connection.   The 20% squeeze rule still applies, but it seals on the face of the o-ring, not the ID and OD.  The distance between the depth of the o-ring groove and the face of the other mounting surface must be 80% of the o-ring cross section.
   When used as it is in the fuel rail connection tubes and T fittings, the seal is solely on those inner and outer cylindrical surface and smooth bores.   Unless they're loose, compressing the carbs by tightening those rod nuts actually has almost zero effect on those o-ring seals.  Seriously.   I mean,  there needs to be end play in that joint, where T fittings still pivot, right?   How does tightening those bolts do anything? 

[HayHauler]

7 ft lbs is NOT very tight.  Same as the exhaust nuts.

Hay 
Jimmyt

[rug_burn]

I just read back-  Timbo already said the almost same thing. Oops.