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Why no in-line fuel filters?

  • Thread starter Thread starter jtolbert
  • Start date Start date
J

jtolbert

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So, it seems like everyone thinks that my GS shouldn't have an in-line fuel filter. I'm tired of getting junk in the carbs (mostly cause the two tanks I have are either rusty or looks good but really unknown)...I'd rather just clean out a filter every now and then. Is there a performance/engine-problem reason for no in-line fuel filters, or am I safe to run one?
 
You need a low pressure (as in no pressure) filter. Should be okay with the right filter but you need to do some homework to make sure you get the proper type.
 
Some people run into starvation. I have used a cheap filter with success that i only paid like 3.99 for at the local motorcycle store. You want a "low grade" filter so that it doesn't restrict the flow, as our bikes pretty much run on gravity and a few psi of flow
 
The problem with the inline fuel filters is they frequently cause fuel starvation.
The GS's have a gravity feed system (no pump or pressure). Most fuel filters are intended for vehicles that have a fuel pump so those filters are too restrictive. Lawn and garden tractors operate on 1 lb of fuel pressure from a diaphram type pump, but the problem with them is the flow is only sufficient for a 15 hp garden tractor which isnt enough for a GS. For full throttle operation, you need a filter that will flow around 3 1/2 ounces per minute by gravity feed utilizing no more than an 6-8" head (height of the tank above the carb fuel inlet) My experience has been that inline filters cause more problems than they solve. The best solution is to fix what is causing the problem rather than taking a "bandage" approach.

E.
 
jtolbert said:
So, it seems like everyone thinks that my GS shouldn't have an in-line fuel filter. I'm tired of getting junk in the carbs (mostly cause the two tanks I have are either rusty or looks good but really unknown)...I'd rather just clean out a filter every now and then. Is there a performance/engine-problem reason for no in-line fuel filters, or am I safe to run one?
Click to expand...

My 26 year old 750 had one when I got it and it worked fine but was yellowed with age and I was concerned about being brittle. So I went to the local MC shop and got 2 more gravity filters - one for a spare. You can also get one from a lawnmower shop but it will cost more and be bigger. They are directional so make sure you don't put it in backwards...easy to do. get a short piece of extra hose to route it under the tank. (This helps avoid pinching the original line.) Look for arrow in the clear plastic. My tank isn't particularly rusty inside that I know of and it still has the original screens on the petcock to keep most any dirt out. I am a believer of these small but effective units. Besides there are 4 bowls full of gas that would have to go empty before starvation would occur under full throttle. It's never happened to me.
 
Clean the tank and no more problems. I did the filter thing and did have a few problems "but" I think what Earl has to say and what "twistedwankel" (what a name:wink:) have merit. My feeling is to just get rid of the problem (thanks Earl) and I think you will not have anymore worries. Check the filters at the needle and seats (they do have fuel screens) and clean out the tank and check the fuel screen at the petcock. I run pretty fast on my way to work and I do run the fuel bowls pretty low and things get a bit shaky as far as carb tuning and sometimes it may rear an ugly head of improper tuning. Hey, Maybe a few minutes of prevention may prevent a few bucks of cure. :)
 
Right on!

Right on!

earlfor said:
The problem with the inline fuel filters is they frequently cause fuel starvation.
The GS's have a gravity feed system (no pump or pressure). Most fuel filters are intended for vehicles that have a fuel pump so those filters are too restrictive. Lawn and garden tractors operate on 1 lb of fuel pressure from a diaphram type pump, but the problem with them is the flow is only sufficient for a 15 hp garden tractor which isnt enough for a GS. For full throttle operation, you need a filter that will flow around 3 1/2 ounces per minute by gravity feed utilizing no more than an 6-8" head (height of the tank above the carb fuel inlet) My experience has been that inline filters cause more problems than they solve. The best solution is to fix what is causing the problem rather than taking a "bandage" approach.

E.
Click to expand...

A sound suggestion based on wisdom and experience......
 
Yeah, there are four float bowls. There are also four cylinders and each cylinder is consuming (or should be) fuel at the same rate. A float bowl holds aproximately 2 ounces of gas. As soon as you have used two ounces more than has been put in, I can say for certain, you will run out of gas. :-)

E.


 
Yeah, I understand that a clean tank would be the best option. That's what I thought I had. The bike ran great for a week, then it seems like something got in to the carbs somehow. The tank has been coated before...Any way to make sure it's nice and clean?
 
jtolbert said:
So, it seems like everyone thinks that my GS shouldn't have an in-line fuel filter. I'm tired of getting junk in the carbs (mostly cause the two tanks I have are either rusty or looks good but really unknown)...I'd rather just clean out a filter every now and then. Is there a performance/engine-problem reason for no in-line fuel filters, or am I safe to run one?
Click to expand...

The reason you dont need an in-line filter is because you already have one that's INTERNAL. All GS's come with a strainer thats bolted to the petcock. Adding a second external filter like Earl commented will starve the flow if you have rust sediment inside the tank. Many GS suffer from rust sediment bouncing around inside the tank. This is the #1 issue that causes major fuel system woes...
 
I have inline filters on both bikes. These are the small yellow plastic ones which are for gravity fed bikes. No starvation issues.

But.. they are not 100% effective. I still get some fine sediment swirling in the bowls after a couple of years.

OTOH, I haven't had to clean the carbs in two years. And at least on the 550 (with its tiny idle jets) that's probably something.

If you do install one, make sure its done properly. It should sit vertically between carbs #2 and #3 with the bent nozzle pointing up and towards the petcock. I like to use clear fuel line so I can watch the gas flow.

I tried an automotive paper filter once on the 550 and I got starvation. Avoid those.
 
just a suggestion, but it might not even be what u think. maybe just maybe u didn't get carbs cleaned good enough the first time
 
Never had a problem with run-of-the mill Fram universal style in-line filters from the local auto parts store. I used the big clear one on my previous bike and a smaller metal one (clearance issues) on the new one with nary a problem. Father-in-law also has the metal one on his 750. Keeps the crap out of the carbs, costs just a few bucks, easy to install...

The screen on the petcock is nothing compared to a real fuel filter. It just keeps the large debris out. The one on my 650 was torn away a bit -- are you sure your petcock screen is still perfectly intact?

If you have any doubt about the ability of a filter to flow fuel, hook one up to your gas tank, turn it to prime, and drain a bit of gas into a jar as you observe the flow. So far mine have all flowed about the same as the line does without the filter. These are relatively small engines and they just sip the gas. Think about how far/long you can drive around on one tank and then think about how fast the gas must be flowing out for a tank to last that long (not very fast). Compare that to the results of my fuel flow test described above. Then install a filter and enjoy your clean carbs.
 
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filters

filters

I have a inline filter on my 1100 i got from autozone and have had no problems at all just make sure the fuel line are as short as possible
 
Well that settles it. My GS1100 had a clear, inline filter and replaced it with a new one that looks exactly the same.
I have sucked the 4 bowls empty a few times now. I'm going to first check the routing of the fuel line to make sure it's not having to climb any hills, but after some reading around here I think I'll just eliminate this one variable. I cleaned out the tank already so this extra filtering shouldn't really be an issue for me.
 
your tank vent is important to check as well.
I run an inline filter, alum screw together body with stone filter 5/16 in/out, vertical mount between carbs with right angle brass fitting toward petcock. GS 1100/1166, cams, open pods, ported heads and no fuel starvation probs since I opened up the tank vent.
 
paco13 said:
your tank vent is important to check as well.
Click to expand...


I THINK that if that were an issue in my case I'd have vacuum in the tank when I open the cap. Every time my bike has starved out (3 times) that has not been evident.
 
jtolbert said:
So, it seems like everyone thinks that my GS shouldn't have an in-line fuel filter. I'm tired of getting junk in the carbs (mostly cause the two tanks I have are either rusty or looks good but really unknown)...I'd rather just clean out a filter every now and then. Is there a performance/engine-problem reason for no in-line fuel filters, or am I safe to run one?
Click to expand...

they do cause a lot of problems
 
i use a snowmobile filter.. just gravity fed with the little gold stone. no problems yet.. do i NEED it? probably not. does spending an extra couple bucks for a little peice of mind seem excessive to me? nope.
 
I had a problem on my 1100EZ of the motor dying on me at the most inopportune times (re: FAR from home). A real 'ghost in the machine' that drove me freakin' crazy. On and off for two years this would happen. I traced and found overheated stator wires (since soldered at the connections) and renewed the in-line fuel filter that had been on the bike for ten years, but the only remedy that cured it for good was eliminating the in-line fuel filter completely and going back to an intact fuel line. Haven't had this "ghost" re-appear since and that was 6,000 miles ago. DO NOT use an in-line fuel filter!
 
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