Fuel filter: to external or not?

[plastx]

I am currently in the midst of a top-to-bottom restoration/renewal/ maintenance on my wife’s beloved ’87 K75S, and when I am through, will start the same on my ’98 R1100RT with 14K miles. I consider myself a reasonable DIY mechanic. At the present time I am not sure whether or not to place the fuel filter externally. An independent BMW dealer that I know and trust states 1) that a fuel filter replacement on the R1100RT is worse than a PITA, 2) he has seen an increasing number of fuel filter problems with the volatility of gas prices (dealers running their tanks to near empty prior to refilling them at the gas station), and 3) he couldn’t/wouldn’t put a filter externally due to liability concerns. Here’s how I put it together at present:
Pros (for an external filter):
1) Turns a PITA routine maintenance into a five minute job.
2) In the event of a clogged fuel filter on the road, would get you back on the road in short order.
Cons (against an external filter):
1) A leak in the apparatus could lead to a dangerous situation. This event could likely be minimized by the use of proper high pressure components (high pressure line and clamps, all metal fuel filter).
What else am I missing? I would appreciate other’s viewpoints on the subject. Thanks.

[PGlaves]

Only you can really assess those risks but I offer this: An external filter adds 2 clamped connections outside the tank to the existing 8 such clamped connections. Done properly the two clamped connections at the filter are no riskier than the 8 existing ones. In addition to that, if you wish you can eliminate 4 of the OEM clamped connections, or for sure two of them by eliminating one or both of the quick disconnect pairs. The one on the pressure line becomes unneeded because you can loosen that line at the filter to pull the tank. You can also just disconnect the return line at the hard pipe from the regulator. This approach eliminates the 4 clamps at the disconnects, and eliminates what I consider to be a much more serious risk than two more clamps: the fragile plastic disconnects and leaky O rings which have a bit of a history of failure.

I would also add this: The OEM filter is an aluminum can with one crimped end intended to be inside the tank for safety. You can get a good automotive fuel injection system filter - steel can with a welded end instead - designed for external mounting. In my opinion a steel welded filter can designed for external mounting is preferred. A defective weld might leak but the end won't pop like a defective crimp. And the leak should be evident the first time you turn the key and activate the pump. Observe it before you button things up!!

[DrPaul]

Here’s how I put it together at present:
Pros (for an external filter):
1) Turns a PITA routine maintenance into a five minute job.
2) In the event of a clogged fuel filter on the road, would get you back on the road in short order.
Cons (against an external filter):
1) A leak in the apparatus could lead to a dangerous situation. This event could likely be minimized by the use of proper high pressure components (high pressure line and clamps, all metal fuel filter).
What else am I missing? I would appreciate other’s viewpoints on the subject. Thanks.
I also have a '87 K75S and have just completed a complete fuel system overhaul. I have a '02 R1150RT as well, also with the filter-in-tank setup that I have changed twice. Of the two, the K bike is a much easier filter replacement job as access to the tank innards requires simple removal of the filler cap assembly and draining/siphoning out enough fuel to get to the filter hose clamps. And where ya gonna hide that ugly old external filter? There's not much distance from the tank nipple to the fuel rail and you might end up having to route the line a ways to hide it.

I'll admit, I'm always a bit anxious working inside the tanks around gasoline vapors ... keep your self and tools grounded and do it outside!

Dr. Paul

[PGlaves]

I also have a '87 K75S and have just completed a complete fuel system overhaul. I have a '02 R1150RT as well, also with the filter-in-tank setup that I have changed twice. Of the two, the K bike is a much easier filter replacement job as access to the tank innards requires simple removal of the filler cap assembly and draining/siphoning out enough fuel to get to the filter hose clamps. And where ya gonna hide that ugly old external filter? There's not much distance from the tank nipple to the fuel rail and you might end up having to route the line a ways to hide it.

I'll admit, I'm always a bit anxious working inside the tanks around gasoline vapors ... keep your self and tools grounded and do it outside!

Dr. Paul

I see no real reason to relocate the K75/K100/K1100 filters. They are accessible by merely removing the fuel cap assembly. It might be a bit messy if there is a lot of fuel in the tank, but should you have a spare with you it is a 10 or 15 minute job beside the road.

On the Oilheads it is a different story. Generally tank off, empty, remove plate (hope you have a spare O ring because the old one is probably too swelled-up to go back in. Vent hoses too short may need to be disconnected - hope you have spare itty bitty clamps ..... I could go on but you get the picture.

There are several OK places to relocate a filter to be external on Oilheads.

[deilenberger]

I would also add this: The OEM filter is an aluminum can with one crimped end intended to be inside the tank for safety. You can get a good automotive fuel injection system filter - steel can with a welded end instead - designed for external mounting. In my opinion a steel welded filter can designed for external mounting is preferred. A defective weld might leak but the end won't pop like a defective crimp. And the leak should be evident the first time you turn the key and activate the pump. Observe it before you button things up!!

Paul, just a thought here.

The R1200R has a revolutionary idea - an external fuel filter, located under the tank in an easy to get to location (it only took BMW from 1983 to come up with this..!)

I looked it up in REALOEM.COM - and found the PN: 13537694732. In cross-checking this PN - it is model specific, ie - it only is used on the new Roadster. If I had to hazard a guess - BMW feels this filter is safe for external use.

Here is the drawing on REALOEM: http://www.realoem.com/bmw/showparts.do?model=0398&mospid=49569&btnr=16_0650&hg=16&fg=05&hl=14, it's PN-14. It is cable-strapped to the bottom of the tank. It uses hose clamps to hold the hoses on (PN-9).

Just a FWIW - for those of us who want to keep our BMWs all OE.. this seems to be a reasonable alternative, especially for external mounting.

Best,

[plastx]

First of all, I apologize for the confusion- I see no need whatsoever to modify the K bike filter- a five minute simple maintenance procedure; my concerns were strictly limited to my R1100RT.

Second, I so appreciate the feedback- it is what makes the MOA Forum such an incredibly valuable resource for those of us with more limited experience and knowledge.

[BubbaZanetti]

for your viewing curiosity:

http://bubbazanetti.smugmug.com/gallery/2707009#143436384

i tried a couple different placements on the S, but wasn't satisfied with any of them. the first one, as described in the IBMWR article i felt put way too much contact between the fuel hose and the edge of the fins on the cylinder barrel. attempt number two (this time with a steel bodied Deutch filter instead of the BMW internal filter) resulted with the filter being up behind the battery. good, but nagging fuel starvation issues (probably in my head, but i was always worried) led me to putting it back in the tank. the routing for that placement behind the battery was a bit weird and i think the tank was crushing the fuel line a bit where it went up over the abs unit, never felt comfortable about that.

[bikerfish1100]

i had the same placement concerns in doing it for my S.
Derek- that shot of it underneath the R side throttlebody looked like it might have been a pretty workable location. what decided you against that option?

[PGlaves]

On Voni's R1100RS and my R1150 R the filter is crosswise above the air filter under the seat. The pressure hose comes from the tank to the filter on the right side. From the filter a hose goes around the left side, forward, back across the top of the engine near the telelever, and the rearward to the hard pipe to the regulator. The only downside to this placement is the extra $$$ for about 5 feet of hose.

[PGlaves]

Paul, just a thought here.

The R1200R has a revolutionary idea - an external fuel filter, located under the tank in an easy to get to location (it only took BMW from 1983 to come up with this..!)

I looked it up in REALOEM.COM - and found the PN: 13537694732. In cross-checking this PN - it is model specific, ie - it only is used on the new Roadster. If I had to hazard a guess - BMW feels this filter is safe for external use.

Here is the drawing on REALOEM: http://www.realoem.com/bmw/showparts.do?model=0398&mospid=49569&btnr=16_0650&hg=16&fg=05&hl=14, it's PN-14. It is cable-strapped to the bottom of the tank. It uses hose clamps to hold the hoses on (PN-9).

Just a FWIW - for those of us who want to keep our BMWs all OE.. this seems to be a reasonable alternative, especially for external mounting.

Best,

Excellent! I didn't know that about the R1200R. I will look at that filter to use instead of the Deautz in the future.

[BubbaZanetti]

Derek- that shot of it underneath the R side throttlebody looked like it might have been a pretty workable location. what decided you against that option?

that was where i was having issue with the fuel line. i think the fuel rail to the regulator is different on the S model and as such, causes the hoses to connect much closer to the cylinder than on other models (correct me if i'm wrong here someone with S and other R bike experience).

if you note in this picture:

http://bubbazanetti.smugmug.com/photos/143436431-M.jpg

the hose leaves the filter then travels behind the tb up to the fuel line, it has to make a pretty tight bend to connect properly. that hose is also touching the cylinder fins all the way behind the throttle body.

[JimMoore]

Definitely externalize. I've been externalized since 1998.

Jim Moore

[jingdog]

1) A leak in the apparatus could lead to a dangerous situation. This event could likely be minimized by the use of proper high pressure components (high pressure line and clamps, all metal fuel filter).
What else am I missing? I would appreciate other’s viewpoints on the subject. Thanks.

If you have an accident the filter could be crushed and leak if it is externally mounted. You could get pinned under the bike unable to move and the fuel could ignite.

[deilenberger]

If you have an accident the filter could be crushed and leak if it is externally mounted. You could get pinned under the bike unable to move and the fuel could ignite.Or the tank could be crushed and start to leak, or a hose ripped loose.

Lots of scenerios - probability is - won't happen if you mount the filter inboard of the cylinder heads.

[PGlaves]

If you have an accident the filter could be crushed and leak if it is externally mounted. You could get pinned under the bike unable to move and the fuel could ignite.

I use steel welded filters, between the frame rails under the seat. The odds of crushing that filter are a lot less than the odds of puncturing the fuel tank. Sure it could happen in theory but if I worried about that probability I would never ride a motorcycle and probably ought not get out of bed.

I can talk about one set of probablilities: one dose of water in your fuel can clog your filter. For most riders a clogged Oilhead filter inside the fuel tank is a trailer or flatbed ride to a dealer someplace. And preventive maintenance won't help you one bit. The filter could be new and still clog with a dose of water. Ever hear of water in gas? Or crud? Ever take a road trip?

You have to assess the risks for yourself. I have, for me.

[Mika]

I have been helping a friend with a Cage project. A small part of the project involved changing and relocating gas tanks. In that part of the project the car went from having an internal fuel pump to an external. This leaves me wondering about not only taking the fuel filter external but the pump also.

Would anyone care to comment?

[BubbaZanetti]

I have been helping a friend with a Cage project. A small part of the project involved changing and relocating gas tanks. In that part of the project the car went from having an internal fuel pump to an external. This leaves me wondering about not only taking the fuel filter external but the pump also.

Would anyone care to comment?

not a good idea, pump uses gas as a heat sink of sorts

maybe if you could get it out in the wind and epoxy some fins to it:laugh

[Mika]

I understand the way the internal pumps use fuel as a coolant. What I am wondering about is applying a pump desinged as an external pump and applying it to a BMW.

[jingdog]

I use steel welded filters, between the frame rails under the seat. The odds of crushing that filter are a lot less than the odds of puncturing the fuel tank. Sure it could happen in theory but if I worried about that probability I would never ride a motorcycle and probably ought not get out of bed.

I can talk about one set of probablilities: one dose of water in your fuel can clog your filter. For most riders a clogged Oilhead filter inside the fuel tank is a trailer or flatbed ride to a dealer someplace. And preventive maintenance won't help you one bit. The filter could be new and still clog with a dose of water. Ever hear of water in gas? Or crud? Ever take a road trip?

You have to assess the risks for yourself. I have, for me.


He wanted to know about EXTERNALLY mounting the filter. Like on the OUTSIDE of the bike. He wanted to know about any downsides. I just pointed out one he didnt think of. Wasnt trying to make his mind up for him. But now that you mention it. The worst that can happen with leaving the filter
in the tank is you might have to walk but you wont burn. With the filter not in the tank you wont have to walk, but you might burn. I did say MIGHT!

[bikerfish1100]

I understand the way the internal pumps use fuel as a coolant. What I am wondering about is applying a pump desinged as an external pump and applying it to a BMW.

should be able to, as long as you use one designed to be mounted externally. we bought one to send fuel from an auxialliary fuel cell into the main tank- but it only operates for a few minutes at a time, and only when Iron Butting.
you thinking of this as a "gain something" project, or as a "want to see if i can do it" project? what do you see as the likely gains/

jingdog- i think we understand thet you proposed a "possible" bad scenario. others have reminded you that your "possible" is not a very likely one, and probably doesn't really need to be considered. i mean, i could devise an anti-asteroid shield for my bike to prevent the eventuality of being hit by one; but there really isn't much likelihood of that happening, so why worry?

[riderR1150GSAdv]

I have mounted the filter externally, as bad fuel can cause blockage. I wouldn't want to deal with the internal filter on a trip as you than need to drain most of the fuel in a canister you don't have..... I have had water in my fuel here where I live and changing the filter took 2 minutes...YMMV. Just my 0.02 cts

[jingdog]

jingdog- i think we understand thet you proposed a "possible" bad scenario. others have reminded you that your "possible" is not a very likely one, and probably doesn't really need to be considered. i mean, i could devise an anti-asteroid shield for my bike to prevent the eventuality of being hit by one; but there really isn't much likelihood of that happening, so why worry?


Oh Im not worried. There are a lot worse things that are much more likely to happen riding a motorcycle than having it burn up from an externalized FF. BMW wont externalize the FF because with hundreds of thousands of mc's out there sooner or later a few of them would have a freak accident and then they might get sued. Suzuki though has no problem putting the oil filter of its DL1000 naked right behind the front wheel.

[Mika]

you thinking of this as a "gain something" project, or as a "want to see if i can do it" project? what do you see as the likely gains/



Think of it as a mind experiment or mental project.

Long story short – a BMW mechanic in Oregon thought I needed a new fuel pump while I was on an extended trip in ’03. $400.00+ I didn’t have so I ran it on the rest of the trip. I have a Roadster that was subject to the early recall for the clamps and quick connect fuel line parts turns out that was all I needed.

Since then I have been wondering as I ride, if and when I finally need to replace the fuel pump on the bike why couldn’t I do it externally? My main goal would be ease of repair in some distant location, and it wouldn’t hurt that I have found pumps that would seem to meet the task for significantly less money.

Thank you for the feed back to my hijack.

[PGlaves]

Think of it as a mind experiment or mental project.

Long story short – a BMW mechanic in Oregon thought I needed a new fuel pump while I was on an extended trip in ’03. $400.00+ I didn’t have so I ran it on the rest of the trip. I have a Roadster that was subject to the early recall for the clamps and quick connect fuel line parts turns out that was all I needed.

Since then I have been wondering as I ride, if and when I finally need to replace the fuel pump on the bike why couldn’t I do it externally? My main goal would be ease of repair in some distant location, and it wouldn’t hurt that I have found pumps that would seem to meet the task for significantly less money.

Thank you for the feed back to my hijack.

If the pump is designed to be external and if the pump delivers at least enough fuel at an appropriate pressure it simply becomes a plumbing problem. It will take modification to the tank so that fuel is directed from the tank to the pump inlet. I haven't really tried to design the new plumbing arrangement but it isn't anything that can't be devised, I'm sure. Worth it? I don't know. Voni's R1100RS still has the original fuel pump with 340K miles on it, so they can last a very long time. Whether they all do, or more specifically whether one person's specific pump will is the question with the unknown answer.