Source for I.D. Dimensions of Fuel Line Fittings?

[Ignacio]

As I'm converting over my fuel cell from the Gen 1 bike to the new Gen 3 I'm taking the opportunity to make sure my various fittings are flowing as much fuel as practical. While I know it's *supposed* to be a 3/8" system I've found several points along the line are likely 5/16".

Which gets me thinking that the that's the inner diameter of my fuel line, but various barbs, filters, valves, and buldhead fittings all go inside that 3/8" line and then have a different actual inner diamater. In fact, I've found actual measurements of pieces in my system (e.g. brass barb couplers) varying from 0.220" to 0.280".

So, now that it's become a longer story I'm wondering of anybody knows of an online resource for the inner dimensions of things that fit inside of things that are rated at dimensions like 3/8"? It's probably in a chart somewhere that shows 1/4", 5/16", 3/8", 1/2", etc. Or what's the name of the standard for things like brass barbs that I might be able to Google a little more intelligently?

I know I'm not going to get to an actual 0.375" flow with a 3/8" system, but I'm hoping to validate a theory that I can get to some figure closer to the 0.280" range by upgrading barbs, quick couplers, and fuel filter...which would be about 60% better flow than my old system.

Thanks.

 

[Twigg]

https://www.pegasusautoracing.com/document.asp?DocID=TECH00096

https://www.plumbingsupply.com/pipethreadsizing.html

https://en.wikipedia.org/wiki/AN_thread

With some fittings, especially "flared" fittings, the angles can vary too. They may still seal, but it's not guaranteed.

 

[Ignacio]

https://www.pegasusautoracing.com/document.asp?DocID=TECH00096
https://www.plumbingsupply.com/pipethreadsizing.html

https://en.wikipedia.org/wiki/AN_thread

The first shows what the dimnension is for I.D. of the fuel line....not the dimension of a coupler that would be used to connect the two fuel lines. It is interesting that the I.D. of a 3/8" isn't .375" as the fraction would suggest, but 0.34", but doesn't answer my question.

The second seems to have something about 5/16, but not 1/4 or 3/8....or other similar measure. I don't think National Pipe Thread (NPT) is a relevant standard here.

I'd already reviewed the Wiki thread about AN fitting (an interesting and nice standard itself), but doesn't share anything about specific dimensions of a coupler in line and only refers generically things like the 3/8" rating.

To simplify, where's the chart that shows what the ID for the 3/8" barb should be with two or three digits of precision?

It may turn out there isn't a standard and actual measurement is the only way, but I'm really only interested in I.D.s of things like barbs, fuel filters, valves, and bulkhead fittings that go inside the hose....not the hose itself.

Thanks.

 

[Twigg]

Try this one:

https://www.eldonjames.com/pdf/thread-specs-and-barb-dimensions.pdf

 

[Ignacio]

Try this one:
https://www.eldonjames.com/pdf/thread-specs-and-barb-dimensions.pdf

You rock. That was really what I needed.

And I see now the dimensions do vary as much as I thought...also depending on material. It doesn't technically include brass, but I've had my suspicions confirmed on some things.

Thanks.

...now I think I may consider some light drilling of some select pieces that are weak links in the chain.

 

[majicmaker]

Light drilling will work. I've had to do that many times. Pay attention to the wall thickness and it'll work just fine.

 

[Justin]

And don't forget the Ballectomy

 

[Ignacio]

No thanks Justin. No need IMO. I've NEVER had a case the cell didn't transfer. In high temp days I use a spare key to open the tank if needed. That way I only smell gas rarely....instead of most of the time.

 

[bigjohnsd]

If you are converting and improving, why not shift to the AN fittings, from my experience plumbing Sprint Cars fuel systems they are much more consistent in flow across various fittings within a given size?

 

[Ignacio]

If you are converting and improving, why not shift to the AN fittings, from my experience plumbing Sprint Cars fuel systems they are much more consistent in flow across various fittings within a given size?

I did think about AN-6, but haven't found a bulkhead fitting low enough profile for use under the tank, I'm not altering the cell any, the few quick couplers I've seen are exceedingly expensive, and braided lines (not that I have to do that with AN, but it looks like it should go together) tends to wear nasty holes in body plastic without doing a bunch more fabrication. At that point it didn't make sense to try and convert just the fuel filter area to AN. No my improvement is intended to just make sure I'm not unnecessarily necking down to a narrow orifice and making sure things are as-reasonably-consistent diameter through the whole system as practical.

 

[Fred W]

No thanks Justin. No need IMO. I've NEVER had a case the cell didn't transfer. In high temp days I use a spare key to open the tank if needed. That way I only smell gas rarely....instead of most of the time.

Not sure where you got that idea from. I ran my '05 for years after gas cap castration, never once smelled fuel.

 

[Ignacio]

No thanks Justin. No need IMO. I've NEVER had a case the cell didn't transfer. In high temp days I use a spare key to open the tank if needed. That way I only smell gas rarely....instead of most of the time.

Not sure where you got that idea from. I ran my '05 for years after gas cap castration, never once smelled fuel.

From two different people that have done a ballectomy.

 

[Twigg]

No thanks Justin. No need IMO. I've NEVER had a case the cell didn't transfer. In high temp days I use a spare key to open the tank if needed. That way I only smell gas rarely....instead of most of the time.

Not sure where you got that idea from. I ran my '05 for years after gas cap castration, never once smelled fuel.

From two different people that have done a ballectomy.

So now I don't know whether to do this or not

On the one hand, I know Iggy's mileages and experience, on the other some folk say the "ballectomy" causes not a gas smell.

I don't know whether to be safe or sorry!

 

[Fred W]

No thanks Justin. No need IMO. I've NEVER had a case the cell didn't transfer. In high temp days I use a spare key to open the tank if needed. That way I only smell gas rarely....instead of most of the time.

Not sure where you got that idea from. I ran my '05 for years after gas cap castration, never once smelled fuel.

From two different people that have done a ballectomy.

Did they have aux fuel cells? Maybe that was why, when they transferred the fuel it pushed the vapor out?? Even then, the vapors should have exited the vent tube down under the bike. They must have had very sensitive noses.

After I castrated mine I dropped it on a hill where the fuel tank ended up being down hill from the rest of the bike. Not intentionally, I assure you. But not a drop of fuel spilled.

 

[Ignacio]

Just to update--I finished reinstalling my fuel cell with fresh 3/8" fuel line, various brass fittings easily drilled to a consistent 0.28" diameter ID, some spiffy anodized hose clamps, and several hose routing revisions that helped smooth radius of lines, shorten the overall length, and compliment fuel filter positioning. However, with all these efforts the quick disconnect (even though I upgraded to 3/8" rating) is still the smallest constriction point. It didn't allow for drilling to the larger diameter given the mechanics of the valving.

But, it's proportionately upgraded from whatever the ID was on a 5/16" unit I was using and the results were promising. Transfer rates sitting in the garage seemed improved from previous experience. The bike is nearly ready for a shake-down ride after this, major electrical wiring, and one last project to upgrade the horn.

Thanks all for the support on my little mini project. Hopefully I can get another 130K miles out of the upgraded cell.