Inline fuel filters: yay or nay?

[wright123]

Intending to clean my fuel tank, I opened my petcock tap and retrieved the fuel strainer. To my horror the "new" strainer that the bloke who sold me the bike installed had been torn wide open for god knows how long, allowing all sorts of gunk into the carburettor which may explain why the engine wouldn't fire at full throttle.

I've therefore been considering getting a separate fuel filter as a secondary line of defense in case the strainer rips open again. Opinions online seem pretty conflicted; I'm worried that putting a filter in would overly restrict fuel flow. Hondas didn't come with them when new.

What do we think?

 

[ancientdad]

Some inline filters cause distinct slowdowns in fuel delivery, sometimes because they're installed backwards according to fuel flow and sometimes their design is the issue (sintered iron filters come to mind as fuel flow problematic for gravity feed models like ours).

Also, though it isn't important in this situation, please remember to mention your bike model or add it to your signature so we don't have to look at your profile to know.

 

[Windmill John]

ancientdad is right for some. There was a type of paper filter that used to breakdown pretty quickly; probably a cheap Mann copy. This did cause issues with one of my old bikes. On bikes that didn’t have a filter in their tap, I’d fit a cleanable glass filter, fitted with a gauze. I’ve just removed the tap from my CM400 and it does not have the filter in place. For the moment, I’m going to fit a little inline filter and when I can get a glass one, I’ll replace it, or if financially flush, I’ll buy a new tap with built in filter.

 

[eamartin]

Intending to clean my fuel tank, I opened my petcock tap and retrieved the fuel strainer. To my horror the "new" strainer that the bloke who sold me the bike installed had been torn wide open for god knows how long, allowing all sorts of gunk into the carburettor which may explain why the engine wouldn't fire at full throttle.

I've therefore been considering getting a separate fuel filter as a secondary line of defense in case the strainer rips open again. Opinions online seem pretty conflicted; I'm worried that putting a filter in would overly restrict fuel flow. Hondas didn't come with them when new.

What do we think?

Old bikes. Old tanks. Old petcocks. I always install an aftermarket fuel filter.

 

[EzPete]

The only issue I've run into with them - outside of just age and failure and needing to swap it out - is that in extreme temps you can get some vapor lock if there's any water in the fuel. With ethanol content and sporadic riding, that can be a concern.

 

[BHSarc]

I used inline filters for a few months. Like you, I read various opinions. I also disliked their look. As of last fall I no longer have them. My tank interior looks pretty good (so far). Guess I'm living dangerously.

 

[stl360+450]

Like many things, inline fuel filters can be done well or done poorly. I tried the plastic cone style early in my vintage bike history and had issues with them clogging and even spontaneously cracking into two pieces after a couple of riding seasons. I would say they are never a solution for a dirty or rusty tank and it's better to focus effort on getting the tank sorted in those cases.

On the other hand, there are fancier inline fuel filters, e.g., glass ones, that probably work well. And if the plastic ones are replaced regularly they may function well. If the tank is clean, I don't see any need for them.

 

[ericfreeman]

I've had problems with the cheap ChiCom fuel filters and stopped using them. I prefer the OEM Honda screen in the petcock for reliability and simplicity. However, if you want a good filter, Pingel makes a nice aluminum filter that has a removable element that can be cleaned. Pricey but you never need to replace it.

 

[CarnivorousChicken]

I used to run in-line filters as a matter of course, but I'm running my 550F without them and so far no problems. That being said, the tank is spotless inside, and the petcock rebuilt with a new screen.

On a 350F I have in Phoenix, I relined the tank and when I mounted it and rode it around for a while it was fine, and then it started starving for fuel. Luckily I installed a filter -- it was clogged with some gunk that came out after I relined the tank (the lining was fine, I probably should have just rinsed it out a couple times). So I was glad I had the filter as opposed to 4 gummed up carbs. Switched it out, and I was good to go.

I've never had running problems with filters, and I've never had one fail (crack or break). I had one that lasted a good 15 years or more. I think as some others have mentioned it partly depends on the condition of your tank and/or petcock.

Bottom line, I'm not against them...

 

[Mikey G]

Usually yay. The fuel flow issues have always seemed overblown to me, and if your filter is filling up fast enough to restrict fuel flow, you've got bigger problems.

The only exceptions I personally would make are some of the early Hondas, specifically for me my CB750 and my 305 Dream. This is because the petcocks on those also function as sediment bowls. Very common on tractors, and in some ways superior to paper or bronze filters.

 

[ancientdad]

This is because the petcocks on those also function as sediment bowls.

Most Honda petcocks from the '70s have sediment bowls and above them is typically a screen that fits above the sealing o-ring for the sediment bowl. I've never personally run fuel filters, though I do have one on my 450 but the purpose was more for a "reservoir" for extra fuel because I'm feeding two 36mm Mikunis from a single 5.5mm line. A decently clean tank is the best solution.

 

[wright123]

Thanks for the advice chaps, I'll take a look at those pingel filters.

 

[Greybeard70]

I have an aftermarket petcock on my CB450 K5 and it was causing restriction to the flow causing issues at high speeds. I installed individual inline filters that use sintered iron and have had no more issues. The filter for the ride side is actually run inside, between the carburetors. I needed more distance due to the length of the filter.

 

[Windmill John]

Look at the size of this behemoth! I ordered it from a classic bike shop. I’d ordered one before, but that one was easily half to a third the size of this!! It physically will not fit between tank and carb inlet. I thought maybe we can all share it to feed all our bikes
I‘ve ordered a basic one until I can track down another glass one smaller than this; which I know exists, I’ve had one.
.

 

[AmericanIron]

Newbie vote, for what it's worth:

When you add an inline filter you are adding another point of potential failure. It's one more thing to have to check in the case of a suspected fuel delivery problem. Unlike the petcock screen, most of them are difficult to evaluate -- you can blow in it or run fuel through it, but there's always a matter of judgement about how much flow is enough. And this is all for, what? To catch particles which are small enough to pass through the petcock screen. Correct me if I'm wrong, but the stock screen on my 175 is pretty darn fine. There is not a single orifice in a Keihin carb which could be blocked by something that makes it through that screen -- a screen which can still get clogged whether or not there's another filter downstream:


I think there's a case to be made for adding a finer filter, *if* the petcock screen is removed. Then it's still one filter to deal with if there's a problem. The idea of two filters in a row on the same line, I just can't see it.

Full disclosure, I may be influenced by what I found on the 175 when I bought it. Literally the first thing that got removed:

 

[Windmill John]

You mentioned something that I’ve always operated by. As long as the mesh is smaller than the smallest jet way, I’ve never worried. I do appreciate a tiny bit can hold open the float valve, but that should be easily dislodged by fuel. Personal feeling, not scientifically proven!