Regan Brown
The Honda CB350 is a popular motorcycle, but some owners have experienced issues with the fuel line. Some have reported that the stock petcock causes problems with fuel flow, leading to a clogged fuel line. This issue can be resolved by priming the fuel lines or by replacing the petcock with a high-quality aftermarket part. It is also important to ensure that the fuel tank is clean and free of debris, as this can cause the fuel line to become clogged. While some owners have suggested using inline fuel filters, others have cautioned that this can lead to starvation issues, especially if the fuel tank is dirty.
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Fuel line size
The fuel line size for a vehicle is important to get right, as too small a diameter will affect performance, while too large a size can be dangerous.
For a Honda CB350, the fuel line size is a topic of much discussion. Some sources suggest that a 3/16 inch fuel hose fits tightly over the fuel nozzles on the petcock and the inputs on the stock Keihin carburetors. So tightly, in fact, that lubrication is required to fit it in place. This size of the fuel line can be purchased from AutoZone, made from solid American-made rubber, and is sold by the foot.
However, other sources suggest that the inline fuel filters on a CB350 are problematic, causing issues at high RPMs. The suggestion is that the flow from the petcock is poor, and the float bowls can become starved. This is compounded by the fact that the petcock will not shut off, even with a new whizzer valve gasket. The recommendation is to have a direct line to the carbs, without the filters, to improve flow.
The setup of the filters is also important, with one user suggesting that the filters be placed below the carbs, so that fuel travels up through them. This will allow fine particulates to wash away from the filter surface and settle in the low spot on the fuel line.
Another user suggests that the OEM rubber carb boots are a good option for the CB350, as they smooth the airflow, which is turbulent without them.
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Clogged fuel lines
If you're experiencing issues with your Honda CB350 motorcycle, such as a clogged fuel line, there are several troubleshooting steps you can take to identify and resolve the problem.
First, check for any blockages or restrictions in the fuel flow. Remove the petcock bowl and screen; if you notice fuel dumping out, the issue is likely with the fuel lines. If there is no fuel, the clog is likely internal. In this case, you'll need to drain the tank and remove the petcock. Use a carb cleaner and compressed air to clear any blockages, ensuring all passages are clean and rubber seals are intact.
If your tank is rusty or degraded, clean it thoroughly before considering a replacement. Improper tank lining can cause flakes to enter your fuel, damaging the tank. If your tank has debris, consider using in-line filters to prevent clogging.
Another potential issue is air bubbles in the fuel line, which can restrict fuel flow. To address this, remove both fuel lines with the petcock off, and hold the rear line under the rear petcock nipple. Turn the petcock to reserve, allowing fuel to drip into the line and for trapped air to escape. Repeat this process for the front line.
If your fuel switch is clogged, you may need to drain the tank and clean or replace the fuel petcock. Rebuild kits are often a cost-effective solution, providing new seals and parts. To prevent future clogs, consider coating the inside of your fuel tank with a suitable chemical treatment, such as por15.
Finally, ensure your fuel lines are the correct size. While a 3/16" fuel line can fit tightly on the CB350's fuel nozzles and stock Keihin carburetors, some owners have reported leaks with this size. Others have opted for 1/4" lines, but these could potentially flood the carbs. The stock fuel line size for the CB350 is 5.5mm, which may be the best option to ensure proper fuel flow without leaks or flooding.
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Fuel flow issues
The Honda CB350 is a motorcycle that has been in production since 1968. It is a popular choice for motorcycle enthusiasts due to its simple design and ease of maintenance. However, one common issue that owners of this bike have faced is fuel flow problems, which can be caused by various factors.
One of the most common causes of fuel flow issues in the Honda CB350 is a clogged fuel line. Over time, the fuel lines can become blocked with debris, rust, or other build-ups, restricting the flow of fuel to the engine. This can cause the bike to lose power, sputter, or even stall. To resolve this issue, it is recommended to drain the fuel tank and clean or replace the fuel lines, as well as the fuel filters and petcock. It is also important to ensure that the fuel tank is clean and free of any rust or debris that could contaminate the fuel system.
Another potential cause of fuel flow issues is air bubbles in the fuel lines. The stock petcock on the Honda CB350 is known to allow air bubbles to enter the fuel lines, which can restrict fuel flow and cause the engine to stall. To remedy this, it is recommended to prime the fuel lines by removing them and allowing fuel to drip into the lines until any trapped air escapes.
In some cases, fuel flow issues may be caused by problems with the carburetors. The carburetors on the Honda CB350 can become clogged or dirty over time, affecting fuel flow and engine performance. It is recommended to clean or rebuild the carburetors and float valves periodically to ensure optimal fuel flow and engine performance. Additionally, issues with the fuel filters or fuel pump can also cause flow problems and should be checked and replaced if necessary.
It is important to note that while using a larger fuel line size, such as 3/16 inches, may not directly cause fuel flow issues, it is recommended to use the correct fuel line size specified by the manufacturer. Using a larger fuel line can affect fuel flow and engine performance, and it is possible that it may contribute to flooding or overflow issues.
To summarise, fuel flow issues in the Honda CB350 can be caused by various factors, including clogged fuel lines, air bubbles, carburetor problems, or issues with the fuel filters or pump. Proper maintenance, including regular cleaning and replacement of fuel system components, is essential to ensure optimal fuel flow and engine performance. Additionally, using the correct fuel type and ensuring a clean fuel tank can help prevent fuel flow issues and keep your Honda CB350 running smoothly.
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Fuel filters
A 3/16-inch fuel hose can be used on a CB350, but it fits very tightly over the fuel nozzles on the petcock and the inputs on the stock Keihin carburetors. It is recommended that you lube the end with a little oil to get it on.
Now, onto fuel filters.
There are a few different types of fuel filters that can be used on a CB350. One common type is an inline fuel filter, which is installed directly in the fuel line. These filters can be made of various materials, including screen mesh, and typically have a 1/4-inch inlet and outlet. It is important to mount these filters correctly to avoid fuel starvation issues, especially if your fuel tank is particularly dirty. One recommended method is to run the fuel lines down from the petcock in a low "U" shape and place the filters below the carbs, so that fuel travels up through them. This helps wash away fine particulates and prevents clogging.
Another option is to use a filter sock on top of the petcock, which can help catch larger debris and prevent it from entering the fuel lines. However, some people choose to remove the stock filter setup and use an aftermarket replacement instead. For example, one CB350 owner replaced their petcock with a steel natural gas line threaded tee and 1/4-inch brass nipples, which improved fuel flow and served the same purpose as the original petcock.
It is important to regularly check and clean your fuel filters and lines to ensure they are not clogged and are functioning properly. This includes checking the petcock bowl and screen, as well as the fuel tank for any signs of rust or debris. If your fuel lines become clogged, you may need to drain the tank and clean or rebuild the petcock, or consider coating the inside of the fuel tank with a product like POR-15 to prevent rust and debris.
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Fuel tank maintenance
Yes, a 3/16 inch fuel hose can be used on a CB350, but it fits very tightly over the fuel nozzles and the inputs on the stock Keihin carburetors. You may need to lube the end with a little oil to get it on.
Now, here is some information on fuel tank maintenance for the CB350.
Firstly, it is important to keep the fuel tank clean and free from debris, rust, and gunk. If the tank is not properly maintained, it can become clogged, leaky, or even ruined. To clean the tank, drain any gas into a can, remove the petcock, and plug the hole. Then, pour in a cleaning solution such as EvapoRust, Caswell, or Por15, and rotate the tank every 12 hours so that all parts of the tank are submerged. Drain the solution back into the jug through a rag, and then wash the tank with water.
Next, dump in a few bottles of 99% isopropyl alcohol, swish it around for a couple of minutes, and then drain it. You may also want to consider coating the inside of the fuel tank with chemicals to prevent future clogs. While performing maintenance, be sure to wear gloves and eye protection as the chemicals can be dangerous.
Additionally, it is important to regularly clean and re-gap the ignition points and spark plugs. This should be done about every 3000 miles. The Honda CB350 has a weak ignition system, so be sure to gap the spark plugs to a minimum of about 0.025".
Finally, if you are experiencing issues with your fuel line, it may be necessary to prime your fuel lines, especially if you have recently changed the lines or filters. If you are running the stock petcock, an air bubble in the line can impede or restrict the flow. To do this, remove both fuel lines, hold the "rear" line under the rear petcock nipple, and turn the petcock to reserve. Allow fuel to drip into the line and escape through the drilled gas cap until it starts to spill over, and then slide the line on the nipple. Repeat for the front line.
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Frequently asked questions
Yes, a 3/16 inch fuel hose fits tightly over the fuel nozzles on the petcock and the inputs on the stock Keihin carburetors.
You will need to drain the tank and remove the fuel petcock. You can also try cleaning the petcock bowl and screen, and if that doesn't work, you might need to rebuild it.
An air bubble in the line can restrict flow. Inline fuel filters can also cause issues if the tank is particularly dirty.
It is recommended to run the fuel lines down from the petcock and place the filters below the carbs so that the fuel travels up through them. This will help wash away fine particulates from the filter surface.
