Topic: Replacing OEM K1 750 Fuel Lines?

[ZTatZAU]

I'm trying to source and replace the OEM fuel lines on my 1971 (s/n 107218X mfg. 12/70) K1 CB750.  Just when I thought I had discovered what I need, I find myself trying to dig my way out of another K1 parts list rabbit-hole.



As seen above, there apparently were three different size fuel lines used on K0, K1, & K2 750s.  However, my OEM fuel lines don't appear to be what''s listed, based on the serial number breakouts shown in my K1 750 parts list.

I can't be sure if the ID of my OEM lines are 5mm or 5.5mm but the OD of my original lines is no larger than 8.4mm as opposed to the 10mm OD I am seeing for the genuine Honda 5.5mm fuel lines on 4into1.com

Can anyone explain these discrepancies or tell me what fuel lines I should be searching for? And where I might find them?

Thanks!  ZT

[Kevin D]

My 11/70 K1 uses 5.5 mm hose. I’d bet yours does too.

My s/n is a bit below 71336, yours is just over.
My parts book is similar to yours.
Looks like I have the wrong hose (I don’t think so)
Go figure.

[ZTatZAU]

My 11/70 K1 uses 5.5 mm hose. I’d bet yours does too.

Appreciate your reply Kevin!
Can you tell me the OD of your 11/70 K1 5.5mm hoses?
Are your ODs 8.4mm or 10mm?

Thanks!  ZT

[Kevin D]

OD doesn’t count, I have some in a box somewhere….. don’t have time to look just now, sorry will check later today. 5.5 is standard.

[bryanj]

I very much doubt your pipe is original and as Honda say use bulk hose purchased localy it wont be original size, 5.5mm id is correct for pipe but get ethanol resistant

[BenelliSEI]

My 11/70 K1 uses 5.5 mm hose. I’d bet yours does too.

My s/n is a bit below 71336, yours is just over.
My parts book is similar to yours.
Looks like I have the wrong hose (I don’t think so)
Go figure.

+1 to that. Last time I bought a small roll of motion pro grey 5.5mm I.D. Hose.  It works great and stays soft for a long time

[jakec]

https://www.ebay.com/itm/361538699424

[ZTatZAU]

My 11/70 K1 uses 5.5 mm hose. I’d bet yours does too.
My s/n is a bit below 71336, yours is just over.
My parts book is similar to yours.
Looks like I have the wrong hose (I don’t think so)
Go figure.

Kevin, based on my K1's S/N being above 1071336, I'm perfectly willing to accept that my OEM hoses were indeed 5.5mm ID.  However I'm still trying to determine if the OEM 95001-55190-40 & 95001-55350-40 hoses OD was 8.4mm rather than the 10mm OD hoses I'm finding on-line.  Can anyone answer this simple question?

OD doesn’t count, I have some in a box somewhere….. don’t have time to look just now, sorry will check later today. 5.5 is standard.

And of course Kevin, the OD shouldn't really matter unless you're going for the original look, size and continued use of the smaller spring wire hose clamps that were on my 8.4mm OD OEM hoses.  Please let me know what you find when you have time to look in that box!

I very much doubt your pipe is original and as Honda say use bulk hose purchased localy it wont be original size, 5.5mm id is correct for pipe but get ethanol resistant

Sorry BryanJ; but I can assure you that my current fuel hoses are indeed original to the bike as I bought my 71 K1 750 brand new in 1971 and neither the carbs or the fuel hoses have ever been removed until only recently.

+1 to that. Last time I bought a small roll of motion pro grey 5.5mm I.D. Hose.  It works great and stays soft for a long time

Thanks for that info BenellySEI!  I'd be interested to know the OD of the 5.5mm Motion Pro Gray hose that you bought.

Thanks again to all who've replied!

[bryanj]

I am amazed your fuel pipe lasted that long, especially with the ethanol in fuel now, when i was in the trade i dont remember there being any option on od for the 5.5 id hose which was not easy to find and the 1/4 always leaked a bit.

[Kevin D]

ZTatZAU, all this discussion is stirring up memories of a nasty episode, and likely I have discarded the original hose and PIA wire clamps.
 My bike was off the road 1987-2002. Removing the fuel tank for cleaning in 2002, the rock hard original hose pulled a spigot out of the petcock. I went to several local Honda dealers for new hose and all they offered was 1/4” or 3/16” tygon tubing. I tried both and neither was satisfactory. I was able to repair the petcock.
 The replacement hose came from a member here. I cannot find the details on the transaction, but IIRC he had a spool of the correct ID fuel hose and I bought a lifetime supply. It has served me very well for 20? years and 50000 miles, and I have the spare tubing in a box. Original source unknown and larger OD than original, ID 5.5mm.
 My CB is daily rider quality, and it is my one and only motorcycle. I haven’t read all of your posts but your attention to detail is admirable and you are aiming higher.

[BenelliSEI]

Thanks for that info BenellySEI!  I'd be interested to know the OD of the 5.5mm Motion Pro Gray hose that you bought.

I’ll measure it up next time I am in the shop.

[MauiK3]

I think I got my hose from Yamiya, it worked great, 5.5mm.

[HondaMan]

Back in the [dark?] days of the 1970s the Honda-supplied fuel hose was 5.5mm ID and 8.5mm OD. This had lasted a long time until MTBE appeared in the gas in the 1980s, then the hoses got brittle. Ethanol was even worse about this, beginning in the 1990s.

The material used in the fuel line changed and got much thicker in order to stay flexible longer. At that same time, the red stripe appeared on the hose to help identify it as "MTBE (or later, Ethanol) - resistant". The old fuel hoses would crack from MTBE and ethanol would turn them into a moderately hard plastic along the inner portion where the fuel contacts it. This newer 'red-stripe' stuff lasts a little longer but will eventually become hardened from the ethanol again, usually in about 2 years.

[Don R]

 The "original" hose I got from 4into1 is 5.5 mm ID and 10.9 mm OD.

[Stev-o]

I use 3/16" fuel line from the local auto store, it's not "correct" but inexpensive and easy to source.
Installs tight and no clamp needed.

[Kevin D]

I found the brittle original hose from my one owner K1 and the OD is 8.24mm +/-
The new (2006) replacement hose OD is 10.24mm +/- and no red line.

[Johnie]

Watching this thread. Am needing some fuel lines for my GL1000 project.

[ekpent]

I use 3/16" fuel line from the local auto store, it's not "correct" but inexpensive and easy to source.
Installs tight and no clamp needed.

Me too.

[jlh3rd]

I'm trying to source and replace the OEM fuel lines on my 1971 (s/n 107218X mfg. 12/70) K1 CB750.  Just when I thought I had discovered what I need, I find myself trying to dig my way out of another K1 parts list rabbit-hole.



As seen above, there apparently were three different size fuel lines used on K0, K1, & K2 750s.  However, my OEM fuel lines don't appear to be what''s listed, based on the serial number breakouts shown in my K1 750 parts list.

I can't be sure if the ID of my OEM lines are 5mm or 5.5mm but the OD of my original lines is no larger than 8.4mm as opposed to the 10mm OD I am seeing for the genuine Honda 5.5mm fuel lines on 4into1.com

Can anyone explain these discrepancies or tell me what fuel lines I should be searching for? And where I might find them?

Thanks!  ZT

from your parts list: oem line was 5.0 mm  I.D....NLA...bulk honda line is now 5.5mm I.D. , as shown...
Your measurements are accurate. The original 5.0mm I.D. line is around 8.5 mm O.D.
The current Honda 5.5mm I.D. line measures 10 mm O.D..
..pics.......first is an old k1 fuel line...the second is current Honda...

[jlh3rd]

this is a parts list showing what size and honda part #'s are for the clips since honda's new fuel lines are bigger than original.

[leovich]

It’s a strange thing. Honda is selling this black fuel line as original that is different from the factory fitted grey hypalon outer with red stripe and black neoprene inside, so you can think it’s like a superceeded part but the truth is that grey with red stripe fuel line is still made and you can find from Honda, just order the fuel vapor canister discharge to ground line from the new Africa twin, it is the same fuel hose of the era

[jlh3rd]

New honda fuel line and carb overflow lines , from what I've seen, do not have red lines on them. The new Honda fuel line is black with silver lettering....the carb overflow line is kinda dark with red lettering....
first pic is current honda  fuel line
the second pic , all carb overflow lines, left to right: J.T. Marks - grey with a red stripe but with lettering "4x8" in between the striping....
            The middle line is vintage 70's honda , ash grey with a continuous solid red stripe, yes, honda bikes in early to possibly later 70's , fuel and overflow lines had continuous red stripes.
             the third line is current honda overflow line , dark with red lettering.

[jlh3rd]

It’s a strange thing. Honda is selling this black fuel line as original that is different from the factory fitted grey hypalon outer with red stripe and black neoprene inside, so you can think it’s like a superceeded part but the truth is that grey with red stripe fuel line is still made and you can find from Honda, just order the fuel vapor canister discharge to ground line from the new Africa twin, it is the same fuel hose of the era

interesting....as the honda parts books only show bulk honda line availability for our vintage bikes.....and it's either black or, black/ silver lettering.....black/ red lettering..
..do you have a pic?

[jlh3rd]

these are pics of fuel lines on a early 70's honda 175 and a 550K. These bikes haven't been ridden in decades and were trade ins for the vintage honda shop I frequent. The 550 was last inspected in 1991, and the 175 was 1989.
The fuel lines have a red stripe on them....so do the overflow lines.....

and my '75 original, unrestored 550 F also has the continuous red stripes on the lines......I believe my tank overflow line does also...
red striped honda fuel line appears to have been available and OEM before MTBE or ethanol....

[willbird]

I see that Mcmaster Carr has a 6mm ID 8mm OD Viton tubing. Probably 6mm would require motion pro stepless clamps.