Fuel Supply FAQs
compiled & edited by Kristian #562
Please read the Disclaimer before attempting any work in this FAQ.


For Aftermarket Tanks refer the Aftermarket Fuel Tank FAQ Classic or Aftermarket Fuel Tank FAQ GS

For Mileage Feedback refer the Poor Mileage FAQ

For Carb Issues refer the Carb Misc FAQ

Replacing the Fuel Hose: See the Carb Misc FAQ


by Kristian #562

Removing the Tank:

To do this you should first turn OFF the GAS petcock. Also remove the SEAT. Preferably done with an almost empty Gas Tank.



  1. Remove the fuel line at the Petcock. Use a pair of Pliers to slide the Spring Clip back down the line, then use a screwdriver to prise off the line. Some excess fuel will drain out of the carbs, but itís not excessive, so donít fret and donít SMOKE.!

  2. On the LHS of the bike Just left of the Carbs there is a small Breather Pipe coming down between the Skin of the Gas Tank and the Tank, joined together just beside the carbs with two smaller spring clips. Use small pliers to loosen one then pull the hoses apart. NOTE: On the USA model bikes there are actually TWO vent lines between the tank and tank cover that must be disconnected, one on each side.

  3. Undo the Large Bolt Just at the rear of the Tank. Itís a 10mm. Use an Open-Ended or Ring Spanner or Socket.

  4. Undo the Small Allen Key Bolts Each Side of the Tank that holding the tank to the front fairing. You can also remove the bolts holding the side fairings to the tank, but PERSONALLY I leave these Grey Coloured parts of the side fairing attached & remove the lot. If you do it this way there are:

    Classics up to and including: '96:
    - 4# Small Allen Bolts each side on Tank itself (8# Total Small on Tank),
    - 1# Small Allen Bolt each side attaching Gray Fairing piece to Tank
    (2# Total Small Tank/Fairing)
    - 1# Large Allen Bolt each Side (2# Total Large Tank/Frame).

    Classics from: '97 on: '96:
    - 4# Small Allen Bolts each side on Tank itself (8# Total Small on Tank)
    - 2# Small Allen Bolt each side attaching Gray Fairing piece to Tank (4# Total Small Tank/Fairing)
    - 1# Small Allen Bolt each side attaching Gray Fairing piece to Radiator Fairing (2# Total Small Gray Fairing/Radiator Fairing)

    - 1# Large Allen Bolt Each Side (2# Total Large Tank/Frame).

    If the clips turn, just stick your hand behind the tank fairing & Hold them.


These Photos are for '97on, Many Thanks to Nate for the Heads-up.


OK Thatís all the Bolts. Now if you LEFT the grey fairing bits below the Tank attached, GENTLY disengage them from the FRONT fairing of the bike, by pulling from the bottom and bending upwards. Grey Side Fairing Removal Location ('96 Classic Shown). Do not try to lift off the Tank at this stage. Note that the ďSkinĒ of the Tank remains attached to the Tank. i.e. on My Bike the Red skin on the Black Tank. Do not try & prise them apart.!


OK now that the side units are free, you can lift off the tank. Do this by gently pulling the whole thing back about 5-10mm, then back and upward OFF the Frame. Tank Lifting. Have a Saw-Horse ready or better still a railing with a cloth over it and place the Entire Tank over that. Temp Tank Storage. Lift with one hand under the rear of the Tank and one down from the top into one of the fork wells. Tank Lifting Up.


They are flat Tabs on the Classic, no locking devices. The Tabs on the Tank just push in/pull out, the ones on the grey side pieces/tank, you have to slightly bend the grey pieces out at the bottom, to disengage the tab, which has a small kink in it.

With the Tank off it is a good time to Consider a Petcock Filter Clean and free up your Petcock.


Tank Replacement:

  1. Holding the tank with one hand under the rear of the Tank and one down from the top into one of the fork wells recesses, Feed the tank onto the front round rubber Mounts.Feed it on by lifting the rear of the Tank pushing forward, then gently lowering the rear.Do NOT push it all the way at this stage.Leave a couple of inches from the from fairing.

  2. Now go around the front of the bike and check all three of the plastic locating Tabs on each side line up with the holes in the front fairing.

  3. Check the Breather Pipe on the LHS of the Tanks hasnít jammed under the Tank.Major PITA to remove it again just because of that. For US Models do up BOTH Vent Lines.

  4. Go round the back again and push it forward until all the Tabs slide into place.If you left the lower Gray fairing bits attached to the tank lift them out a bit so they go past the front fairing.

  5. Push the rear off the tank as far forward as you can, place and tighten by hand then torque the Tank retaining Bolt.

  6. Do up all your Allen Key Bolts (NOT TOO TIGHT, some Blue Loctite these closed, but I remove my tank quite a lot).

  7. Reconnect the Breather pipe & Clamps

  8. Reconnect the Fuel Line and Clamps, Turn on the petcock.




Sticky or Hard-to-turn Petcock Problem

by Omnikron

  1. Well for me, my fuel petcock was almost impossible to turn! So I took it outside on a day when I knew I wouldn't be riding the bike (cause I just knew I was gonna get gas all over the place) and unfortunately, I had a full tank.

  2. Please do this OUTSIDE, in a well-ventilated area and do NOT smoke. Keep the Tank and any spilt gas away from Naked Flame, sparks and children.

  3. So #1 recommendation is to have a near-empty or empty tank. If it's not been "driven" to empty, you can simply undo the fuel line from the petcock (Pull the clip back after squeezing with a pair of pliers), drain the GAS into an approved container, and refill it back into the Bike after cleaning, if your Tank is still a bit full.

  4. If you have the Tank OFF the bike, e.g. for a Valve Check, Carb Clean, laying it down on its side on a wad of cloths with the petcock side UP will also allow you to remove it, even with some gas in the Tank.

  5. Switching the Petcock to OFF won't help you.!

  6. Remove the two screws holding the metal casing that surrounds the petcock and slowly and gently remove the cover and the copper-looking washer. NOTE!!: The metal on the bolts and petcock housing is very soft and the threads can ruin easily.

  7. Now you are looking at the petcock from the cross-view and you can turn it back and forth and watch it work, but be careful, because the force of the gas pushing against it will most likely push out the petcock and will spray gas all over the place. Its what happened to me, but I just stuck my petcock back in where it came out of and it held. After that, I sprayed silicon around the edges and all over it. I put it back together and it works wonderfully now. Its SO much easier to turn. I'm not sure if it was the silicon or just the speed of the gas exiting the hole that perhaps cleaned it out but whatever it was, it works a WHOLE lot better now.

  8. You can get Silicone Spray from most auto shops.

  9. There is nothing to it. Just put the washer back on, and if it gives you some trouble trying to get everything to go back properly, just be patient and make sure the washer fits in the groove before you tighten those screws down.

  10. You may need to repeat this at your 10,000kms Service Intervals.


If you happen to strip your petcock screws undoing them, the petcock for the Aprilia Pegaso appears identical to the Funduro classic's, with one major plus; it has a big plastic handle instead of the lame-o lever we've got. Costs about a buck more for the pleasure. NormJ #473.

Hard-to-turn Petcock Experiences


In-Tank Fuel Filter Cleaning

by NormJ #473

Petcock Removal and Tank Screen Cleaning FAQ.

If you have never removed and cleaned your petcock and in-tank screens, you should. And as I discovered when doing my own 24k maintenance, none of the 3 previous dealer 6k services had actually done the work. When I removed the petcock to clean the screens, there was an amazing array of plastic shavings, sand and unidentifiable particles collected on the reserve screen. My guess is that the plastic shavings are remnants from the manufacturing process, and sand and other junk blew/fell into the tank during fueling.


  1. This really should be done with the tank removed for the reasons explained in step 5 below. See the Tank Removal FAQ for details. Also, you should wear rubber/vinyl gloves to prevent neurological damage from the gasoline.

  2. Drain as much fuel from the tank as you can by turning the petcock to reserve and tilting over a suitable container, such as your oil collection pan. You should theoretically NOT be able to completely empty the tank; there is a slight sump wherein water can settle and thus not enter the reserve tube.

  3. Turn the tank on its right side and carefully remove the 2 hex head bolts securing the petcock; it takes a 4mm wrench. I strongly suggest using your high-quality T-handle and taking your time. The metal on the bolts and petcock housing is soft and threads can ruin easily.

  4. Gently remove the petcock by pulling straight out; this would be down if the tank were on the bike.

  5. Gently place the petcock on a cloth. Then, work the tank around to slosh out the remaining gas into your collection pan. You are likely to see more gas than you expected (1/15th or 1/10th of a Litre), plus maybe some water and more particles than you thought you'd see.

  6. Gently clean the gunk from the tubes, screens and the joint where the tubes join the body of the petcock. A soft toothbrush, a little gas, and med-high pressure air are great tools. The long tube appears to be removable by simply pulling it free, but it is not necessary for cleaning it well.

  7. If you are having trouble with the lever being sticky or stubborn, CAREFULLY remove the two small screws holding the plate and lever in place. BEWARE - the petcock body is very soft. Several inmates have ruined their petcocks by stripping the metal when disassembling or screwing the plate back on. Clean and reassemble as per the Sticky Petcock FAQ.

  8. Gently reinsert the petcock into the tank and re-secure the bolts; be careful, you're screwing them into plastic. Be Gentle. At this stage you're wondering, should I use a Sealant? Mine and quite a few others didn't leak, the gasket was just fine, but I guess in case it dribbles, a sealant is one cure, although a new gasket might be a better solution. If you use a sealant, then find one one NOT affected by Petroleum.

  9. If you have not yet installed an inline fuel filter between the petcock and the carbs, I highly suggest you do it now. I found several particles in my filter that I cannot understand how got past the petcock screens.


So can I clean it without removing the TANK?

Classic F650

by Johnny #862

  1. Maybe I'm the last one here to figure this out, but the fuel screens can be cleaned (or the petcock replaced, in my case) without pulling the fuel tank as instructed by the factory manual. It takes a bit of fidgeting with the Allen wrench, but it can be done. I didn't take the time to do it, but best would be to weld about a foot of steel rod to the 4mm Allen wrench needed so you could get at the two securing screws from below the bodywork. As it was I loosened the panel under the fairing at the front two 3mm screws and that provided room needed to get the wrench in there. The screens were perfectly clean at 9k miles but there was quite a collection of black plastic shreds at the base of the screens which were likely left overs from machining the tank. Pretty harmless sitting there.

  2. Ah, sorry, yes, it's a '98 classic. I should have mentioned too that I was impulsive enough to take this on with a full tank. Holidays now so I felt I have the time to do this. I used a manual gas pump from Griot's to remove several gallons and then pulled the gas line off the petcock and replaced it with a short piece of tubing to drain the rest (on reserve, of course). I can't tell that there was anything wrong with the original valve, but I was definitely able to ride for miles with it closed occasionally. I might have massaged the old valve and got it to work. I did take it apart and could find nothing obviously wrong, but neither could I explain why at times I could run for miles with the thing off. The replacement, "Made in Italy" is only about $20 so I just replaced it. This one is much stiffer to turn!




Close the Fuel Tap?

Q. In the BMW owners manual, it says to "ALWAYS CLOSE the fuel tap when the engine is switched off"...I've never heard that... I've only thought to turn the fuel tap off when I'm storing it long term.

Aftermarket Fuel Filter FAQ
by Steve Johnson, F6501, updated by Kristian #562

In-line Fuel Filter
This filter is similar to Prime Line #7-02357 and available at O'Reilly Auto Parts.

One very necessary item that every bike should have is an external fuel filter. A see-thru type is the best. The rider can see what kind of garbage is collected before it gets to the carb. Easy to install and cheap, it is the best insurance around. Shut off the gas, cut a short section out of the line, and install the filter. Be sure to check for correct flow direction, usually indicated by an arrow on the fuel filter. See photo.

Here's a close up of a couple of Aftermarket Fuel Filters.



Note the following when buying/installing a fuel filter.

Fuel Filter Vapor lock?

Q. I installed an aftermarket filter on my '97F. It's a glass one with replaceable element from Pep Boys ($10). I notice that it doesn't usually fill up with fuel. Sometimes it does, but more often it just has a little in the bottom and you can see it trickle in the top as the bike is running. That's my first question - why doesn't it fill up, located under the tank as it is? About 400 miles into my Saturday ride this weekend, I hit reserve. Pulled off to go to a gas station about ten miles later. Waiting at the stop light, the bike dies and it won't restart. I push it off to the side, pop the gas cap and shake the bike around to see if I can hear any fuel in there. I do hear some sloshing, then the filter starts filling up. Then, of course, the bike started. What was going on?

What about Clamps to re-attach the Hoses?


Gas Tank Lock

Q. Does anyone know of an alternative to the BMW for a new lock cylinder?

The key broke off in the lock for the gas cap. Drilling the lock through worked well enough to remove the cast piece for the cap. Further filling and hammering with a nail set removed the the remaining bits of the lock. The most frustrating thing has been the dealer. When asked about price for a new cylinder they quoted me $280 Canadian. After regaining my composure I said all I needed was the lock cylinder and that couldn't be the right price. In fact that is price of the cast piece that bolts to the tank. They then looked further and a found a price of $130 for a lock and key. But I must give them my key code. There must be another source for such a small piece. I seem to remember others inmates mentioning European car repair shops a possible source. Does any one have specifics on this? That is, a car model that uses the same lock or better yet an actual part number. Adrian#668, 97 Funduro, 01 Dakar.

A. Nope. Not yet. Sorry.

Removing the Gas Tank Restriction for easier filling.

(NOTE!: Appears to ONLY apply to US Models and WILL VOID your WARRANTY)

Filling a "classic"....from a gas can or at a station is not pleasant. The small hole keeps you from seeing how much you put in and at the station the spring thing that surrounds the hose nozzle (at least here in NJ) doesn't fit into the larger opening ; just scratches whatever it contacts. A while back someone mentioned that they cut off the small hole with a hacksaw thereby eliminating most of the unpleasant part of filling up. It enables you to see better and the spring thing can be held back so no contact is made with the tank. I'm sure doing this is easy, but I thought many of us would like to as well and any additional comments and/or suggestions would be appreciated. It's really a good idea and the thought of not struggling each time I fill up makes this surgery a "must".


Where does the "Fuel Cap Drain" Drain to?

Q. I have a 98 classic, and I seem to remember when I first got it if I spilled some gas when I was fueling into the little black channel around where the nozzle goes that it would disappear. This is no longer happening. I went to fill up the other day after a heavy rain and I opened the cap to see all this liquid running from that channel into the gas tank. This is not a good thing as it was water but the bike has run ok since anyway just don't want to make a habit of it. My question is is there supposed to be a drain for this channel and if so where does it go? What do I need to do to check to see if this is clogged? If anyone has some pictures that would be great.


Gas Cap Vent Cleaning?

by Flash 412 (CO)

Q. I assume I have to take it apart to clean it? Are small pieces and springs or something going to come flying out? Fairly recently somebody on the site said the check valves in the cap can get plugged up. In the FAQ it says "If the canister is gone, then the hole in the vent cap may be clogged with dirt" or some words to that effect.
A. The gas tank vents via a hose, not through the cap. Revisit the Canisterectomy FAQ.

The cap lets pressure past the seal between the cap and the inside of the inner tank to the area between the cap and the outside of the inner tank. You are not looking for a hole that goes THROUGH the cap to the outside air. You're looking for the action of the spring-loaded portion of the cap that contacts the inner tank in order to "vent" properly. The spring loaded thing need withdraw only slightly to allow it to "burp" to the enclosed area where the hose hole resides. (I'm not even sure that there is anything to clean or SEE associated with gas tank venting.)

Years ago mc gas caps had a literal hole through them, a vent hole to the air, that became clogged. This hole was generally under the cap, outside the perimeter of the sealing surface of the tank. Sometimes it was even on top, in the middle of the gas cap. It ain't like that no more.

Actually, the interior of the cap is much more complex than most would realize, with a couple flap type check valves. Take it apart some winter just for fun.



How "suddenly" should the effects of running low on gas kick in?

Q. Last week, I was riding downhill on a curvy dirt road when my engine sputtered once or twice and then very quickly shutdown. So fast in fact that my rear wheel locked up and sent me high-side before I could engage the clutch. Sure enough, when I dusted myself off and picked the bike back up, it was at about 150 miles and wouldn't start back up until I turned the fuel tap to reserve. This is my first carburetted bike in a while, but I still tend to think I should have a little more warning before running out of fuel. Any advice would be great.

A. Sudden (engine) death.


Broken Tank Support Bracket


Not a common Breakage Item!


BRACKET 46 51 2 345 258. Marty #436-Chicago-97 F650F



Water in the Tank?


Q. Filler cap leakage? Is it possible to get water into the fuel tank from my filler cap, even if locked when for example I wash the bike or under some heavy rain?
A. Yes. It is also possible to get water in the tank from condensation AND from filling up while the truck is delivering gas to the station. Flash



Removing the COLOURED SKIN off the Tank?

by Flash #412

Q. Is is possible to remove the plastic body panels off of the fuel tank without removing the fuel tank? In the fuel tank removal section of the FAQ, is says that you aren't supposed to pry them apart, but does that mean that it is an unnecessary step, or that it cannot be done? My intention was to remove the plastic so as to modify (paint) it... I was hoping it would just pop off with minimal hassle. Robert in Texas #959 -- Black '97 Classic.

A. You can pull the color part off the tank without removing the tank. Take all the screws out between the cover and the fairing. Take all the screws out between the cover and

the engine covers. Take the rear bolt out. Removing the CAP is a bit tricky. You need to be especially careful not to over tighten anything when you reinstall it.




Where's my Reserve?


Problem: The problem is, it doesn't seem like my bike has a reserve. At about 180 miles (classic F) I run out of gas. Switching to reserve doesn't help. What does help is leaning the bike over to get that last little bit out of the right side of the tank. Could my "reserve" inlet be leaking into the "on" inlet? Any help you can offer will greatly improve my marriage (otherwise known as, my wife is getting sick of standing around in the middle of nowhere while I go off looking for some dirt bikers with extra gas). '97 F650, #1291.

Solution: Run it out of gas. Lean it over to the right. Remove the petcock. Look at the petcock and see if there are two tubes of different lengths on it. If not... fish the missing tube(s) out of the tank and shove it/them back in the hole(s). The LONGER tube is for the ON position. The shorter (or no) tube is for the reserve position. You can figure out which is which by blowing through the tube(s). Flash #412


If you are losing gas, check the PUKING PETROL FAQ.