Project Honda CB450: Fuel System Upgrades

Honda CB450 - Fuel Line, Petcock, Rubber Tank Mount

Among the last things I’ve been working on, I’ve had a couple nagging projects left: improving the tank/fuel system and bringing the front brake system up to 100%.

Yeah, I know what you think. These aren’t nagging projects, they are critical. Fortunately, both the brake and fuel system are operating, but I know they can be improved to be optimal. I hate knowing critical systems aren’t at 100% performance, because I always have the inkling suspicion that one’s about to fail!

For the fuel system, the needed upgrades were a new petcock, new hoses, new filters, a new rubber tank mount and a quick disconnect crossover. I also want to put on a better clear coat on the tank.

Honda CB450 - Fuel Line, Petcock, Rubber Tank Mount

The current blue helix hoses, which I bought at the local motorcycle shop, were bought out of necessity. I had picked up a snazzy pair of polyurethane red fuel lines from Dime City Cycles, but these quickly hardened once fuel sat in them. They promptly started leaking, even with clamps. This was disappointing, as they originally came with no packaging, so they are of unknown make. I’m guessing they weren’t Helix, which is widely sold and used for fuel lines. The blue ones were Helix, but blue doesn’t match my color scheme. So I finally ordered a pair of red Helix lines, as the blue ones are taking on a slightly off color from gasoline sitting in them too long.Tusk Fuel Line Quick Disconnect

The new red Helix lines appeared immediately to be better quality. They fit tighter on the barb fittings at both the carb and the petcock. So tight that hose clamps aren’t needed. I let these sit with gas in them for a few days to check if they broke down or changed in durometer (science term for rubber hardness). They appeared stable, as opposed to the previous lines I’ve tried which hardened significantly. Good stuff.

Next thing to check was the new petcock, which I bought off an eBay store specializing in vintage Honda parts.

This petcock wasn’t NOS (new old stock) but rather a 3rd party part that was built to OEM specs for part numbers: 16950-292-000 & 16950-283-000. It was really cheap too, at only $22.99. Unboxed, it’s identical in nearly every way to the original petcock, but it’s got a nice chrome finish. I don’t think it’s actual chrome but just a plating/finish over die-cast aluminum. It also came with new seals and nylon mesh reserve filter, instead of the old brass mesh.

I also picked up some new fuel filters, this time ditching the sintered brass bead type and instead buying 1/4 Visu-Filters with a stainless steel mesh filter element. Although it may have been my line routing scheme, the previous filters I put on the bike seemed to choke some fuel flow. This may not be because of the brass matrix filter element, but more in the design of these filters: they are long. Because they are long, they add an extra inch of “straight” line to the fuel route, which requires some finagling to route properly for the right side carb (closest to the petcock). The mesh screen filters are half the length. Instead of a cone or arrowhead shape, these are a flat disk shape. This leads to a more flexibility route from petcock to carb. You can add more bend, my friend.

Finally, I also purchased a quick disconnect fitting for the tank crossover line that connects both sides of the tank. This length is the biggest pain when removing the tank, as you’ve got to empty the entire tank every time. No matter how much I try to drain the tank by tipping the bike, even precariously tipping the tank with the crossover still connected, I ALWAYS spill fuel when I finally remove this line. Considering how much time I put in to paint the frame, tank, and motor, this genuinely throws me into an uncontrollable rage.

Unfortunately, the Tusk brand fuel disconnect I bought leaked right out of the box. I reviewed it in the following article. Check this out for more thoughts. 

I also picked up a new rubber tank mount to replace the old ratty one that ripped a long time ago. I had been using a piece of velcro wrapped around the plate before, so I figured it was time to upgrade it.

Aside from this pesky fuel disconnect, everything installed on the bike easily. Here are a few tips to make the job easier:

  1. When you’ve got the tank off the bike, with the petcock removed, insert your finger up into the bunghole and remove any debris caught right around the hole.
  2. Wasn’t Step 1 hilarious to read? I’m sorry, but it couldn’t be said any other way.
  3. Rinse the tank with several cups of gasoline, swishing it around and draining through the petcock hole. Repeat this several times to remove any debris.
  4. As always, check the tank interior with a flashlight for any rust. Keep an eye on any of the rinse gasoline for rust discoloration.
  5. If you find rust, recoat the tank. There are plenty of resources on doing this if you search Google or forums.
  6. Attach the petcock OFF the bike. Once you’ve got it tightened, attach the tank crossover line, and add some fuel. Let it sit for a bit and check for leaks at the petcock. It’s super easy to overtighten it and mash the little gaskets and cause a leak. It’s also very easy to undertighten it.
  7. Take this time to tighten and adjust the petcock correctly so it’s facing outwards in an orientation thats easy for you to access the OFF/ON/RESERVE settings.
  8. Drain the gas by opening the petcock. This lets you flush out any metal bits from manufacturing leftover in the petcock.
  9. Remove the bowl and check it for debris.
  10. Remove the screen element above the petcock bowl and clear that off any debris. If you’ve got bits of metal, rust, paint, or god knows what, flush out the tank again. Consider using a fuel-safe solvent like SeaFoam mixed with some gas.
  11. Attach your fuel lines to the carbs with hose clamps with the tank off. You won’t be able to access the hose-to-carb barbs and tighten a clamp for the inside carbs with the tank on. So do it before hand.
  12. Don’t cut the hoses to the exact length on the first try, about 6 more inches than you think you’ll need to reach where the petcock will be. Lay the hose in the intended route to the tank.
  13. Reattach the tank.
  14. Now, figure out the appropriate lengths, and fuel filter placement sections. I find it easiest to connect the lines to the carbs, then use a marker to indicate where I want the fuel filters to be.
  15. Cut lines with a sharp knife and make sure you its perpendicular. Its very easy to cut fuel lines at a bias.
  16. When routing, try to keep the fuel lines always above the height of the carb BOWLs. This took me a long time to figure out, but it will make sure the fuel is always trying to drain into the carbs, not hung up in a bend and flowing backwards.
  17. With fuel filters, its easiest to attach them closer to the carbs than to the petcock. Since the carb barbs are pointed up, this will help keep you fuel lines always in an upward direction from the carbs. It just makes it harder to check the state of the filter for the inside carbs and requires you to remove the tank to swap them out.
  18. Once you’ve got all this done, make sure your fittings are tight, and add some gas. Check again for any leaks at the petcock and tank crossover.
  19. Turn on gas. Check for flow, make sure you can see gas filling up the filters. Tap the filters to help them fill up.
  20. Pull your bowls and verify you’ve got fuel being delivered to the carbs.
  21. If everything works, go ride!
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