Fuel hose
Posted: Wed Oct 28, 2020 5:44 am
Some have asked why I don't fit new fuel hose to the carburetors I rebuild. There are reasons. But the situation is not a simple one so allow me to explain.
Fuel hose for motorcycles is one of the harder things to deal with when rebuilding carburetors. There just isn't an easy way to handle it. Here are some of the problems. First, very few fuel hose choices are sized correctly. All of Honda's fuel fittings are metric, and 90 percent of the available fuel hose is Imperial. This may seem a minor issue, but it really isn't. There is a pretty big difference between 5mm and 1/4", for example.
Next, Honda often annoyingly puts differently-sized fuel fittings on a given carburetor/petcock combination, meaning that one end of the hose has to fit one size while the opposite end of the same hose on the same bike is forced to stretch to a larger size. Strange, this, but there it is. And quality fuel hose that can fit properly on two different fuel fittings is not real common.
Third, quality. 1970s-era Hondas came from the factory with dual-layer fuel hose. Incredibly good stuff. The outer layer was hypalon, the same thing that covers spark plug wire. The inner was Viton, very high quality. This dual layer hose was so good it resisted decay for over 30 years, what with the outer layer standing up to the ravages of ultraviolet/ozone/etc. many times better than any other hose. So good in fact that I would rather leave still-intact but somewhat-hardened OEM fuel hose on the carbs rather than replace it with anything else I can find. Because that "anything" is going to inevitably be inferior hose. 1
Fourth, though Honda still makes "factory" hose available, it is not this original stuff, but rather a third party substitute. It's fair hose, but not the same as that used in the 1970s and into early 1980s. Interestingly, a certain Japanese importer *does* offer the original Honda red-stripe dual-layer hose. 2 So the equivalent hose is available, just not from Honda. But it is breathtakingly expensive. So, just put the Honda red-stripe hose on, problem solved. Well, that would be fine except the cost is prohibitive for me to include it in the rebuild, and few customers will pay the extra freight for this good hose. And there are other issues. 3 I haven't sold any red-stripe hose in years.
Fifth, quality, again. Motion Pro's best hose is thin-wall, kink-prone, and tending toward hardening. The Geman-made Continental brand braided outer layer stuff, once found on early BMW motorcycles, though it looks rugged, is also very poor quality. Underneath the handsome braiding is near natural rubber hose that softens dramatically as it ages. K&L's Tygon (i.e., plastic) is that famously bad stuff that hardens like a rock-- remember pushrod Brit bikes? And what about auto parts store hose? Except in the 1/4" size, which occasionally can be purchased in a form snug enough to substitue for Honda's 5.5mm original, most auto parts and hardware store stuff is pretty far off size-wise and worse, much of it chunks internally, resulting in debris in the fuel system. One thing I will say for most car hose though, one thing in its favor, at least it is designed to resist kinking, which almost none of the stuff from motorcycle sources can claim.
Sixth and last, and perhaps the hurdle that remains even after the other issues are solved, is this. With various petcock and carb and fuel filter combinations and configurations possible, I have found it is best to let the customer make his own fuel hose arrangements. If I try to anticipate things, all I am doing is wasting product because lengths and curve radii and clamping method and inline filter choices, due to individual bike setup-- are all variables. It's best if I stay out of it, though occasionally I will ship carbs with a piece of hose for the customer to fit as he chooses.
So there you have it. The challenges of supplying my customers with new fuel hose. The choices run the quality gamut. The customer's expectations and configurations vary widely also. And the marketplace is geared toward cheap. And I don't do cheap.
1 Obviously, not if it is already so hardened it will leak. All carb rebuilds are leak-tested.
2 Kawasaki also used this company's dual-layer hose, but their's was marked with a blue stripe instead of a red one.
3 For some strange reason, only the 5.5mm size fits properly. The company's larger 7mm hose for later Honda carbs is quite a bit off.
Fuel hose for motorcycles is one of the harder things to deal with when rebuilding carburetors. There just isn't an easy way to handle it. Here are some of the problems. First, very few fuel hose choices are sized correctly. All of Honda's fuel fittings are metric, and 90 percent of the available fuel hose is Imperial. This may seem a minor issue, but it really isn't. There is a pretty big difference between 5mm and 1/4", for example.
Next, Honda often annoyingly puts differently-sized fuel fittings on a given carburetor/petcock combination, meaning that one end of the hose has to fit one size while the opposite end of the same hose on the same bike is forced to stretch to a larger size. Strange, this, but there it is. And quality fuel hose that can fit properly on two different fuel fittings is not real common.
Third, quality. 1970s-era Hondas came from the factory with dual-layer fuel hose. Incredibly good stuff. The outer layer was hypalon, the same thing that covers spark plug wire. The inner was Viton, very high quality. This dual layer hose was so good it resisted decay for over 30 years, what with the outer layer standing up to the ravages of ultraviolet/ozone/etc. many times better than any other hose. So good in fact that I would rather leave still-intact but somewhat-hardened OEM fuel hose on the carbs rather than replace it with anything else I can find. Because that "anything" is going to inevitably be inferior hose. 1
Fourth, though Honda still makes "factory" hose available, it is not this original stuff, but rather a third party substitute. It's fair hose, but not the same as that used in the 1970s and into early 1980s. Interestingly, a certain Japanese importer *does* offer the original Honda red-stripe dual-layer hose. 2 So the equivalent hose is available, just not from Honda. But it is breathtakingly expensive. So, just put the Honda red-stripe hose on, problem solved. Well, that would be fine except the cost is prohibitive for me to include it in the rebuild, and few customers will pay the extra freight for this good hose. And there are other issues. 3 I haven't sold any red-stripe hose in years.
Fifth, quality, again. Motion Pro's best hose is thin-wall, kink-prone, and tending toward hardening. The Geman-made Continental brand braided outer layer stuff, once found on early BMW motorcycles, though it looks rugged, is also very poor quality. Underneath the handsome braiding is near natural rubber hose that softens dramatically as it ages. K&L's Tygon (i.e., plastic) is that famously bad stuff that hardens like a rock-- remember pushrod Brit bikes? And what about auto parts store hose? Except in the 1/4" size, which occasionally can be purchased in a form snug enough to substitue for Honda's 5.5mm original, most auto parts and hardware store stuff is pretty far off size-wise and worse, much of it chunks internally, resulting in debris in the fuel system. One thing I will say for most car hose though, one thing in its favor, at least it is designed to resist kinking, which almost none of the stuff from motorcycle sources can claim.
Sixth and last, and perhaps the hurdle that remains even after the other issues are solved, is this. With various petcock and carb and fuel filter combinations and configurations possible, I have found it is best to let the customer make his own fuel hose arrangements. If I try to anticipate things, all I am doing is wasting product because lengths and curve radii and clamping method and inline filter choices, due to individual bike setup-- are all variables. It's best if I stay out of it, though occasionally I will ship carbs with a piece of hose for the customer to fit as he chooses.
So there you have it. The challenges of supplying my customers with new fuel hose. The choices run the quality gamut. The customer's expectations and configurations vary widely also. And the marketplace is geared toward cheap. And I don't do cheap.
1 Obviously, not if it is already so hardened it will leak. All carb rebuilds are leak-tested.
2 Kawasaki also used this company's dual-layer hose, but their's was marked with a blue stripe instead of a red one.
3 For some strange reason, only the 5.5mm size fits properly. The company's larger 7mm hose for later Honda carbs is quite a bit off.
I knew there was something wrong with that sentence...