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Here we go. Since there are threads popping up almost daily asking about this problem on older (K7 and up) Burgman 400 scooters I decided to make a better guide.
What this mod does is essentially bypass the internal (hidden and irreplaceable) fuel filter/strainer with an inline one.
Cost is about $10-15 and you also get the gas line replaced in the price (which costs $40 normally from Suzuki).
This mod fixes the following symptoms:
- Bike will not go over some RPM value (typically around 5k or 6k, will drop off with time)
- Bike bogs down under throttle / when accelerating
- Fuel starvation
Time needed: 1-3 hours.
Items needed:
- Universal EFI fuel fiter for cars (8mm or 6mm, both will work):
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- 6mm rubber gas hose, 0.5m in length (I'm not pasting a picture of this, you know what a hose looks like).
- 4 small screw clamps (the ones looking like a ring with a screw to tighten it)
Tools needed:
- Screwdrivers, allen keys
- Dremel
- Scalpel
Now for the steps:
REMOVING FUEL ASSEMBLY
- Remove the seat by unscrewing the 4 bolts that hold it to the bracket. Unclip the under seat light.
- Remove the engine cover plastic by popping the two clips.
- Remove the plastic just in front of the engine, also held by two clips. This is the plastic under the nose of the seat with small vents in the middle / front.
- Remove the rubber L piece connecting the intake and the air box. Might take a bit of 'massaging', don't be afraid to manhandle it a bit.
- Remove fuel from tank if tank is more than half full.
- Unscrew the two allen head screws attaching the fuel hose to the injector (at the top of the engine).
- Unscrew the two allen head screws attaching the fuel hose to the fuel assembly (down where the tank is).
- Remove 6 allen head screws that hold the fuel assembly attached to the tank, they are arranged in a circle, can't miss them if you tried.
- Disconnect the wire going from the fuel assembly to the harness. Might be a bit tricky but try using a thin screwdriver.
- Pull out the fuel assembly. You will need to rotate and wiggle it around. Think of it as a puzzle.
MODDING THE REGULATOR BOX
- You now have the culprit out. Put it on a desk somewhere and remove the two Phillips screws from the sides, down near the bottom of assembly.
- Pull everything apart. Do remember which wires go were. There are only two but still.
- You should now have the bottom cap, fuel pump, regulator box (white box with the float attached) and the 'metal part' with two rails on which everything was assembled. If you do not have those parts you have not pulled enough. Only O-rings hold things in place.
- Remove the metal relief valve from the regulator box, again held in by stubborn O-ring.
- You now have a regulator box with three holes and a float attached to it.
- Look through the holes and you will see a metal mesh inside the box. Might be black or orange or whatever color from the dirt / goo / etc. This is what is causing the problem and can not be replaced. Suzuki requires you to replace the whole assembly for $550 or so.
- Try blowing into the top hole while holding one of the bottom holes closed so that air must pass through the mesh. If it is normal there should be no resistance. Mine took some effort to get a breeze on the other side.
- Take a sharp and thin something. Such as a small screwdriver or sharpened bicycle spoke and poke holes into the metal mesh. It is pretty soft so not much effort needed.
- Blow again, should be nice and easy now.
MODDING THE GAS HOSE
- Since now we essentially do not have the strainer anymore we need to put another, better, filter in.
- To do this take the original hose and cut the metal clamps / rings around the ends of the original rubber hose, where rubber meets the L pieces that attach to injector / tank. Make sure to cut only to the rubber as not
to damage the metal L pieces.
- After cutting through pry the clamps open and remove them.
- Use scalpel or wherever method you have at hand to remove the original hose from the L pieces. It is glued on so will take some effort. Clean them up until there is no rubber left on the pieces themselves.
- The new fuel filter can be mounted just under the nose of the seat, behind that plastic that you removed earlier - with a grille on it, so place the filter there and measure how much hose you will need on the side that goes to
the tank and on the side that goes to the injector.
- Cut the hose to length and force it onto the filter. Some soap might help. Tighten (tightly) to the fuel filter with clamps.
- Do the same to the L pieces. Don't forget to put the clamps and the factory insulation onto the hose beforehand
- Now you should have a hose that resembles the original but with a fuel filter in the middle.
- Use large screw clamp / zip ties to secure the fuel filter to the frame in front of the frame as described above. Image in attachments.
PUTTING IT TOGETHER
- Retrace the steps above in reverse order.
- Massaging the fuel assembly back into the pump takes some patience. Just wiggle and rotate the assembly around and you should be good after a minute or so.
- Make sure to connect the gas tank side of the hose first and prime / remove the air from the filter and hose by turning the key one or two times until the gas flows out of the other (injector) end and then screw it onto the injector. Not
really needed but will save you a few seconds of cranking as gas needs to fill the hose and filter.
Take the bike for the test ride and your problem will almost certainly be gone.
One thing I can recommend is to clean the pouch / filter under the pump before reinstalling or if you want and have one, replace it. To me that thing did not make any difference but some users had a lot of gunk in it.
Have fun
WARNING Make sure that the hose, filter and L pieces are clamped down tight and will not come apart when the fuel hose is pressurized.
These are steps that I did to fix the problem and if you are going to replicate them you are doing it at your own risk as working around gas can be dangerous.
What this mod does is essentially bypass the internal (hidden and irreplaceable) fuel filter/strainer with an inline one.
Cost is about $10-15 and you also get the gas line replaced in the price (which costs $40 normally from Suzuki).
This mod fixes the following symptoms:
- Bike will not go over some RPM value (typically around 5k or 6k, will drop off with time)
- Bike bogs down under throttle / when accelerating
- Fuel starvation
Time needed: 1-3 hours.
Items needed:
- Universal EFI fuel fiter for cars (8mm or 6mm, both will work):
- 6mm rubber gas hose, 0.5m in length (I'm not pasting a picture of this, you know what a hose looks like).
- 4 small screw clamps (the ones looking like a ring with a screw to tighten it)
Tools needed:
- Screwdrivers, allen keys
- Dremel
- Scalpel
Now for the steps:
REMOVING FUEL ASSEMBLY
- Remove the seat by unscrewing the 4 bolts that hold it to the bracket. Unclip the under seat light.
- Remove the engine cover plastic by popping the two clips.
- Remove the plastic just in front of the engine, also held by two clips. This is the plastic under the nose of the seat with small vents in the middle / front.
- Remove the rubber L piece connecting the intake and the air box. Might take a bit of 'massaging', don't be afraid to manhandle it a bit.
- Remove fuel from tank if tank is more than half full.
- Unscrew the two allen head screws attaching the fuel hose to the injector (at the top of the engine).
- Unscrew the two allen head screws attaching the fuel hose to the fuel assembly (down where the tank is).
- Remove 6 allen head screws that hold the fuel assembly attached to the tank, they are arranged in a circle, can't miss them if you tried.
- Disconnect the wire going from the fuel assembly to the harness. Might be a bit tricky but try using a thin screwdriver.
- Pull out the fuel assembly. You will need to rotate and wiggle it around. Think of it as a puzzle.
MODDING THE REGULATOR BOX
- You now have the culprit out. Put it on a desk somewhere and remove the two Phillips screws from the sides, down near the bottom of assembly.
- Pull everything apart. Do remember which wires go were. There are only two but still.
- You should now have the bottom cap, fuel pump, regulator box (white box with the float attached) and the 'metal part' with two rails on which everything was assembled. If you do not have those parts you have not pulled enough. Only O-rings hold things in place.
- Remove the metal relief valve from the regulator box, again held in by stubborn O-ring.
- You now have a regulator box with three holes and a float attached to it.
- Look through the holes and you will see a metal mesh inside the box. Might be black or orange or whatever color from the dirt / goo / etc. This is what is causing the problem and can not be replaced. Suzuki requires you to replace the whole assembly for $550 or so.
- Try blowing into the top hole while holding one of the bottom holes closed so that air must pass through the mesh. If it is normal there should be no resistance. Mine took some effort to get a breeze on the other side.
- Take a sharp and thin something. Such as a small screwdriver or sharpened bicycle spoke and poke holes into the metal mesh. It is pretty soft so not much effort needed.
- Blow again, should be nice and easy now.
MODDING THE GAS HOSE
- Since now we essentially do not have the strainer anymore we need to put another, better, filter in.
- To do this take the original hose and cut the metal clamps / rings around the ends of the original rubber hose, where rubber meets the L pieces that attach to injector / tank. Make sure to cut only to the rubber as not
to damage the metal L pieces.
- After cutting through pry the clamps open and remove them.
- Use scalpel or wherever method you have at hand to remove the original hose from the L pieces. It is glued on so will take some effort. Clean them up until there is no rubber left on the pieces themselves.
- The new fuel filter can be mounted just under the nose of the seat, behind that plastic that you removed earlier - with a grille on it, so place the filter there and measure how much hose you will need on the side that goes to
the tank and on the side that goes to the injector.
- Cut the hose to length and force it onto the filter. Some soap might help. Tighten (tightly) to the fuel filter with clamps.
- Do the same to the L pieces. Don't forget to put the clamps and the factory insulation onto the hose beforehand
- Now you should have a hose that resembles the original but with a fuel filter in the middle.
- Use large screw clamp / zip ties to secure the fuel filter to the frame in front of the frame as described above. Image in attachments.
PUTTING IT TOGETHER
- Retrace the steps above in reverse order.
- Massaging the fuel assembly back into the pump takes some patience. Just wiggle and rotate the assembly around and you should be good after a minute or so.
- Make sure to connect the gas tank side of the hose first and prime / remove the air from the filter and hose by turning the key one or two times until the gas flows out of the other (injector) end and then screw it onto the injector. Not
really needed but will save you a few seconds of cranking as gas needs to fill the hose and filter.
Take the bike for the test ride and your problem will almost certainly be gone.
One thing I can recommend is to clean the pouch / filter under the pump before reinstalling or if you want and have one, replace it. To me that thing did not make any difference but some users had a lot of gunk in it.
Have fun
WARNING Make sure that the hose, filter and L pieces are clamped down tight and will not come apart when the fuel hose is pressurized.
These are steps that I did to fix the problem and if you are going to replicate them you are doing it at your own risk as working around gas can be dangerous.
