Lowsided my freshly converted efi ninja

[k12.usmc]

Soooo, I am ashamed to be on here because less than 24 hrs after getting my bike running again, I lowsided into oncoming traffic literally right in front of the street too my house on my way from home. Pretty much the only factor to blame is me and trying to ride a bike that is basically 100% different the same way I had been riding prior. The bike has incredibly more torque than before. The bike actually sustained less serious damage than me. Basically road rash on the left side and a slightly bent shifter. Me on the other-hand sustained a swollen left foot that is probably broken (the reason I am up at 2 am), a badly scraped up left knee, and a slightly scraped up right knee. Could have been worse, I was wearing all my gear minus riding pants (guess what I will be wearing from now on). What I can take from this is a learning experience. Gonna hang up my jeans and long johns as a reminder. Can't wait to go to the doctor tomorrow for my physical, perfect timing I guess.

[Jiggles]

[k12.usmc]

Originally Posted by Jiggles

This is exactly what I am doing right now.

[akima]

Aww, sorry to hear that Ryan. Another confirmation of the saying "most accidents happen 5 minutes from the destination". Hope you and your efi-machine get healed up soon.

Did efi system really make that much difference over the carb system? I'd love to try a carb bike to get a feel for how it compares to my bike. I've been told that efi bikes can be more jumpy: less smooth when you're adjusting revs.

[k12.usmc]

Thanks Bro. The bike really doesn't have anything wrong with it, minus road rash which looks bad but really isn't and the bent shifter. Me, not so much. Its a good learning experience, though somewhat painful.

But yes, efi and carbs are two different beasts on this bike. My original carbs were totally unresponsive most the time compared to the quickness of efi. It is incredibly jumpy and the torque actually made me do a wheelie without even knowing it or wanting too. The bike is also running rich now bc I dont have the o2 sensors in place yet.

Il post some pics soon.

Update: fractured left foot have to wait till monday to go to the ortho, hydrocodone my new best friend

[gfloyd2002]

Sorry to hear Ryan. Sucks. What exactly happened that caused the lowside? Jumpy, you said, because of EFI. Was it just a question of coming into traffic too hot and then getting too heavy on the back brakes? What would you do differently next time?

With your road rash and ankle, can I ask about what gear you had? Not to wag a finger (I promise not to say anything ), but out of curiosity as to what the rest of us might learn for our own (probably inevitable) low sides.

Hope your ankle heals quickly!

[tazz]

heal soon brother

[NathanUc]

Sorry to hear about that sounds rough. Sounds like it should be a quick fix for the bike and a nice excuse for some aftermarket rear sets

To make light of the situation, when you show up to your physical you should be like "... you mean this stuff isn't normal?! DOC WHAT IS WRONG WITH ME?!"

[k12.usmc]

Thanks Guys! This is one of the primary reasons why I enjoy this forum so much, just a great group of guys.

Originally Posted by gfloyd2002

Sorry to hear Ryan. Sucks. What exactly happened that caused the lowside? Jumpy, you said, because of EFI. Was it just a question of coming into traffic too hot and then getting too heavy on the back brakes? What would you do differently next time?

With your road rash and ankle, can I ask about what gear you had? Not to wag a finger (I promise not to say anything ), but out of curiosity as to what the rest of us might learn for our own (probably inevitable) low sides.

Hope your ankle heals quickly!

Just to clarify, the only thing that's wrong with me is my left foot is fractured and my left knee has road rash. I pretty much wear all the gear all the time. However, when I go to and from school I normally just wear jeans because its a 3 mi trip one way on local roads. Guess what I will be wearing from now on. I think your dead on about what happened. However I am not entirely sure, everything happened so fast. The only thing I was thinking was **** im ****ed, I have two options go into oncoming traffic or make a really quick turn into a safe spot which I lowsided into. I think the best thing that I got out of this is to treat every time you ride treat it like the first time.

Originally Posted by NathanUc

Sorry to hear about that sounds rough. Sounds like it should be a quick fix for the bike and a nice excuse for some aftermarket rear sets

To make light of the situation, when you show up to your physical you should be like "... you mean this stuff isn't normal?! DOC WHAT IS WRONG WITH ME?!"

I went down Thurs night and just so happened that I had a physical Fri morning. I am going to orthopedics on Mon morning.

[gfloyd2002]

Originally Posted by k12.usmc

Just to clarify, the only thing that's wrong with me is my left foot is fractured and my left knee has road rash. I pretty much wear all the gear all the time. However, when I go to and from school I normally just wear jeans because its a 3 mi trip one way on local roads. Guess what I will be wearing from now on. I think your dead on about what happened. However I am not entirely sure, everything happened so fast. The only thing I was thinking was **** im ****ed, I have two options go into oncoming traffic or make a really quick turn into a safe spot which I lowsided into. I think the best thing that I got out of this is to treat every time you ride treat it like the first time.

We've all done this, just that most of us are luckier. I have to admit winding up my ninjette a bit more than usual for the first few rides after I installed my kickass new Area P system. And I've also done the whole "it'll be a pain in the ass to wear the overpants, where will I put them when I get there, its only a quick trip" thing. So I guess we owe you thanks that we get the reminder to gear up and slow down but we don't have to suffer through physical therapy.

I was most curious about whether you wearing protective boots at the time of accident, or just regular shoes? I'm asking because I've been feeling recently that my normal commuting boots (BiLT Trackstars) may not have enough ankle protection, and have been thinking about commuting in something else for just the reason you have so generously demonstrated. I read "fractured ankle on a lowside" and I get nervous.

Also, on losing the rear end, this is one reason I've been contemplating deemphasizing or eliminating rear brake use on stops. Not to start up this debate again on whether or not to use the rear brake, but it makes one wonder. I've been using both, with about 85% front brake on normal stops, but wonder whether having my foot there and getting muscle memory built up using the rear creates a risk -- that being on the rear brake pedal in a panic stop plus adrenaline means putting too much rear brake in and losing the back end. The risk is even higher when under full braking from speed as the weight of the bike shifts far forward under heavy braking, reducing weight and increasing risk of traction loss on the rear. (This is especially pronounced on short wheelbase, light bikes like our ninjettes.) Essentially, if you are at near lockup on the front, as you should be in an emergency, I doubt that the back does much of anything at all on our ninjette. And I can attest to this, as I've done a stoppie, rear wheel totally off the ground, avoiding a van that ran a stop sign. There is even higher risk if you happen to let the clutch out or downshift during a panic stop, as engine braking adds to the drain on traction for the rear wheel. While I know of a study that says using the rear and front perfectly together can reduce overall stopping distance by 5 feet at 150 foot stopping distance (3%), that sure isn't much. And it is tricky business to get that rear brake just right in panic situation -- I'd say not worth the risk of lowside if you don't get it JUST right. May be worth just going all hands (clutch and front brake in), no feet (rear brake).

[akima]

Originally Posted by gfloyd2002

May be worth just going all hands (clutch and front brake in), no feet (rear brake).

You think even avoid using engine braking during an emergency? In the UK, to pass your module 1 motorcycle test they ask you to do an emergency stop. They expect you to only pull in the clutch at the very last moment of just before the engine stalls. You either fail or loose points if you don't do this (can't remember which).

[gfloyd2002]

Originally Posted by akima

You think even avoid using engine braking during an emergency? In the UK, to pass your module 1 motorcycle test they ask you to do an emergency stop. They expect you to only pull in the clutch at the very last moment of just before the engine stalls. You either fail or loose points if you don't do this (can't remember which).

I would say yes, avoid engine braking in an emergency on a ninjette. Engine braking uses the rear wheel to slow you down. You have only a limited amount of traction in that rear wheel before it breaks loose (or brakes loose, he he ). On a short wheelbase, lightweight sportbike, you weight is going to shift forward dramatically in an emergency stop, and engine braking risks losing the rear wheel just like being on the back brake does.

I can see why you might teach differently. On a larger bike, particularly a crusier-type, there isn't nearly as much weight shift. I used to own a Kawi Eliminator 600 (pauses for booing ), and that thing was long and low, with some silly 5+ foot wheelbase and the rider sitting upright by the back wheel, with very little weight shift on deceleration. I would and did use the rear brake and engine braking in all stopping on that bike. And there is an MSF study that backs this up for these bigger, longer bikes, one that was mentioned in my basic motorcycle course -- It found you can stop in 180 feet with just rear, 130 feet with just front, and 95 feet with both. But even in an MSF study with heavy bikes, MSF found that disengaging the clutch was the best way to stop quickly. Here is what it found:

With the goal of reducing the chance of locking the rear wheel and its negative consequences, certain observers suggested not declutching during a hard stop. The rear wheel thus remaining coupled mechanically to
the engine is less susceptible to lock. The mean braking distance recorded over 35 passes with the clutch engaged was 41.51 metres. In the 11 passes for which the rider was instructed to declutch, that is to pull the clutch lever and disengage the rear wheel from the engine, the mean stopping distance was 39.95 metres. In light of these figures we recommend completely declutching during an emergency stop.

When you change to studies less weighted (he he, I did it again ) towards bigger, longer bikes, rear wheel stopping doesn't work as well -- you only get about a 3% advantage using front and rear brakes simultaneously, but at much higher risk. And the disadvantages to using engine braking are going to be even stronger. It is illustrative that there is a difference in utility of using the back wheel for braking. And using the engine is using the back wheel for braking - only I think controlling it takes even more care. On our ninjettes, I think that is a bad thing in an emergency unless you are highly skilled.

[akima]

Originally Posted by gfloyd2002

You have only a limited amount of traction in that rear wheel before it breaks loose (or brakes loose, he he )

Very good points. At present I don't use my rear brake at all except for when I'm coming to a stop (at like 5mph), when braking on loose terrain at very low speeds and when holding the bike still when I'm at a complete stop.

[n4mwd]

Ryan, what kind of riding boots did you have on? I'm thinking I should avoid that brand.

Anyhow, glad you weren't mangled too bad. Sorry about the bike. The shifter is the first thing to go on a Ninja. Fortunately its not too hard to take it off and hammer it back.

Was that an EFI kit or did you put it all together by yourself like greg737 did? I don't recall Greg mentioning any significant increase in HP.

[Boom King]

Originally Posted by akima

You think even avoid using engine braking during an emergency? In the UK, to pass your module 1 motorcycle test they ask you to do an emergency stop. They expect you to only pull in the clutch at the very last moment of just before the engine stalls. You either fail or loose points if you don't do this (can't remember which).

It's interesting how certain techniques are taught differently depending on where you live. In my motorcycle safety course, we were taught to pull in the clutch as you start your emergency braking and downshift all the way to first. We would not engage the clutch until after we had stopped and were ready to move forward again.

[greg737]

Was that an EFI kit or did you put it all together by yourself like greg737 did? I don't recall Greg mentioning any significant increase in HP.

k12.usmc installed an Ecotrons kit for most of the project but he used a Kawasaki OEM FI EX-250 throttlebody like I did in my build. (there are three of us who've managed to get our hands on the OEM throttlebody, I think the third guy is diwhiteii)

About horsepower and torque: Yes, I've been pretty conservative when it comes to claims of increases and I've tried to be realistic in giving credit where it's due. I will say that my FI EX-250 is no doubt faster, livelier. You can definitely feel it. The engine revs more willingly, winding the tach up more quickly than before. I often find myself approaching 13,000rpm, needing to shift.

But it's still a 250 and you know it. I'm pretty sure that if you did a "blind taste test" with experienced riders, nobody would mistake it for a 600.

Maybe some day I'll take the bike to a dyno to get the real numbers.

I'm sure a good part of the performance increase has to be the fuel injection that instantly provides the optimum Fuel/Air ratio for every situation. I'd have to say that the nature or "feel" of my FI EX-250 is very immediate and crisp throttle response and a good overall improvement in powerful. But not so much that you would forget that you're riding a 250cc bike.

But part of the performance increase is, of course, due to the standard (non-FI) performance upgrades I've made to the bike (the Area P exhaust and the K&N pod filter) and also the fact that the bike simply weighs less with the aftermarket exhaust, no center stand, no passenger footpegs.

Overall I think my FI project bike delivers a great performance "feel" for a 250cc bike. With some work (the FI system, the normal performance upgrades to exhaust & intake, suspension upgrades, and "creature comfort" modifications) I've managed to turn my EX-250 into the bike I wanted right from the beginning.

[n4mwd]

I often find myself approaching 13,000rpm, needing to shift.

Mine is just carbs and that's pretty much the standard way to shift for me.

But one thing I would like to know is how has your gas mileage been since you made the change?

There is something wrong with my bike and I haven't figured it out yet. When I first got it, it easily got 70-80 mpg. Then suddenly, its getting 56-60. It doesn't seem to matter how I ride it. I've had numerous theories, but none have panned out. Maybe fuel injection would fix it?

Ecotrons has their own controller, but I think k12 said he was using a microsquirt. It seems kind of pointless to buy the kit if you are just going to do everything yourself anyway.

Also, I noticed the ecotrons uses a plain fuel filter, while your design uses a high pressure filter. Any real differences in fuel quality?

[greg737]

Mine is just carbs and that's pretty much the standard way to shift for me.

I'm not saying that my FI bike operates differently from the carb bike. It just gets there faster than it did on carbs.

But one thing I would like to know is how has your gas mileage been since you made the change?

Even with the "go-fast" stuff on my FI bike, K&N filter and 2-into-1 exhaust, it always works out to right at or just over 60 MPG in a mix of riding (about equal parts highway, stop-&-go city/neighborhood, and "spirited" twisty road riding).

When I do a just long cruise type of ride where it's mostly highway the bike gets 65 to 67 MPG.

Ecotrons has their own controller, but I think k12 said he was using a microsquirt. It seems kind of pointless to buy the kit if you are just going to do everything yourself anyway.

You might have his project mixed up with mine. As far as I know I'm the only one using a Mircrosquirt controller.

Also, I noticed the ecotrons uses a plain fuel filter, while your design uses a high pressure filter. Any real differences in fuel quality?

My setup uses two filters, both are Fram filters. One is a simple paper filter on the fuel line just below the petcock. The other is a high pressure metal cannister filter on the line leading from the pressure regulator to the throttlebody fuel rail. In my setup the simple paper filter below the petcock sees only normal slow-flow demand just like a carbed bike because my system doesn't loop back to the tank. Two filters seemed like a good idea to me. They're cheap and I'll do what I can to insure the injectors stay clean and free-flowing.

But you are asking a good question about the filter Ecotrons uses because, when you think about it, I wonder if that filter they're using was intended for the continuous fuel flow-rate that it sees due to the fuel looping back to the tank from the pressure regulator then out of the tank again through the petcock, through the filter, and back into the fuel pump and the regulator for another loop? Long sentence, I know. But a good question.

There are plenty of higher quality filters on the market that are designed for a lot of continuous flow, so that's would be at the user's discretion to upgrade, I guess.

[n4mwd]

On yours, I was concerned about your looping technique. I'm not sure if you are looping back through the filter, but you should because it could pick up contaminants from the hosing. Especially if there alcohol in the fuel.

Anyway, the thing I was concerned about was that every time gas goes through the fuel pump, it adds a little heat. This could possibly result in a vapor lock situation.

[greg737]

On yours, I was concerned about your looping technique. I'm not sure if you are looping back through the filter, but you should because it could pick up contaminants from the hosing. Especially if there alcohol in the fuel.

On my system the fuel is filtered as it comes from the tank by the simple paper filter. Once the fuel is in the cooling loop of my system it is not filtered, it doesn't need to be. The fuel that is eventually metered out to the injectors is filtered by the high pressure filter. Perfect.

Anyway, the thing I was concerned about was that every time gas goes through the fuel pump, it adds a little heat. This could possibly result in a vapor lock situation.

Yes, fuel system heating is always a concern.

On my system the fuel in my "cooling loop" circulates through a cut-down Flexalite 4130 fuel cooler that's mounted to the bottom of the K&N 0990 air filter. I cut the Flexalite cooler's heat exchange element (the finned part) down to 3 and 1/2 inches so it fits perfectly along the bottom of the K&N. During operation the air filter sucks air across the fuel cooler and keeps my fuel system nice and cool on even the hottest day.

Rounding out my system's protection against heat and vapor problems is that I have a vapor-relief/bubble line that runs from my Suzuki LT-R450 Quadracer fuel pump to what was the vacuum line on my bike's petcock. The petcock's vacuum diaphram has been removed which converts the vacuum port into a useful fuel line.

[n4mwd]

I'm wondering why you chose that method rather than just simply routing the bypass fuel back into the tank through the vent tube like ecotrons does it? It seems a perfect solution as any vapors get trapped in the tank and ultimately condensed back into usable fuel. He also drills a hole in the top which I didn't understand.

[greg737]

I'm wondering why you chose that method rather than just simply routing the bypass fuel back into the tank through the vent tube like ecotrons does it?

Ecotrons hasn't recommended or established the petcock vacuum line conversion. That's my idea that I've put forward as a possible substitue for cutting a hole in a non-California type tank to install a fuel return port.

Why did I choose not to loop the fuel back to the tank? Mainly because at the time I was building my system I hadn't yet thought of the possibility of re-purposing the OEM petcock vacuum line. I also couldn't find an alternate petcock to fit the EX-250 tank.

There's nothing wrong with a fuel system like mine that doesn't return the fuel pressure regulator excess flow to the fuel tank. As long as you've properly addressed the heat and vapor issues one design is as good as another.

He also drills a hole in the top which I didn't understand.

You'll have to be a little more specific/detailed here, I don't know who you're referencing "he" and I don't know where this hole your mentioning is located.

[choneofakind]

Originally Posted by n4mwd

I'm wondering why you chose that method rather than just simply routing the bypass fuel back into the tank through the vent tube like ecotrons does it? It seems a perfect solution as any vapors get trapped in the tank and ultimately condensed back into usable fuel. He also drills a hole in the top which I didn't understand.

@n4mwd are you talking about the instructions here? :
http://www.ecotrons.com/files/Ninja2...anual-v2_1.pdf

Think about this from a constant volume and constant pressure situation. The tank is a fixed volume and it will always get back to normal atmospheric pressure. Normally, the carbs pull vacuum and suck out gas. This creates a low pressure in the tank which is remedied by the breather. In the instructions I linked above, the return is routed through the breather and there is a hole drilled in the top of the tank because the breather is no longer adding air to compensate for all the gas leaving the tank, and even with fuel returning to the tank, there is still a net loss of matter in the tank's point of view. There has to be a way for air to get into the tank to neutralize that negetive pressure; hence the hole in the top. At least, that's what I've gotten from reading about this. Correct me if I'm wrong @greg737

[n4mwd]

Originally Posted by greg737

Ecotrons hasn't recommended or established the petcock vacuum line conversion. That's my idea that I've put forward as a possible substitue for cutting a hole in a non-California type tank to install a fuel return port.

Why did I choose not to loop the fuel back to the tank? Mainly because at the time I was building my system I hadn't yet thought of the possibility of re-purposing the OEM petcock vacuum line. I also couldn't find an alternate petcock to fit the EX-250 tank.

There's nothing wrong with a fuel system like mine that doesn't return the fuel pressure regulator excess flow to the fuel tank. As long as you've properly addressed the heat and vapor issues one design is as good as another.


You'll have to be a little more specific/detailed here, I don't know who you're referencing "he" and I don't know where this hole your mentioning is located.

No, if I read his (="ecotron guy") info correctly, he returns fuel through the vent tube on the back of the tank. Normally this tube just vents the tank through a rubber hose to the bottom of the bike. So its a viable return port. He drills a hole near the filler cap for some reason that I have not figured out. I don't think he does anything with the petcock vacuum line.

With your petcock return system, does the fuel go back into the tank or just through the petcock? I'm thinking it might be possible to modify the rubber washer under the knob and get access to the second inlet so fuel could go back into the tank. Or is that what you have already done?

[n4mwd]

Originally Posted by choneofakind

@n4mwd are you talking about the instructions here? :
http://www.ecotrons.com/files/Ninja2...anual-v2_1.pdf

Think about this from a constant volume and constant pressure situation. The tank is a fixed volume and it will always get back to normal atmospheric pressure. Normally, the carbs pull vacuum and suck out gas. This creates a low pressure in the tank which is remedied by the breather. In the instructions I linked above, the return is routed through the breather and there is a hole drilled in the top of the tank because the breather is no longer adding air to compensate for all the gas leaving the tank, and even with fuel returning to the tank, there is still a net loss of matter in the tank's point of view. There has to be a way for air to get into the tank to neutralize that negetive pressure; hence the hole in the top. At least, that's what I've gotten from reading about this. Correct me if I'm wrong @greg737

Yes that's what I meant. But if you have a fuel pump, why do you care about creating a vacuum in the tank? A lot of cars with FI are sealed and you can hear the vacuum break when you open the gas cap to refill it. Is it possibly because the pump on bike is not strong enough?

[greg737]

n4mdw has pointed out something that I was thinking about:

With your petcock return system, does the fuel go back into the tank or just through the petcock? I'm thinking it might be possible to modify the rubber washer under the knob and get access to the second inlet so fuel could go back into the tank.

He's right (n4mdw), the petcock modification I've been thinking and talking about with him and Matt at Ecotrons and choneofakind needs some further consideration....

Here's the issue: As n4mdw has noticed, the petcock vacuum line modification for fuel return as I've described it so far only gets the return fuel to the chamber in the petcock that is below the petcock's two input tubes from the tank (the "On" tube and the "Reserve" tube). So if the petcock modification is executed as we've been discussing so far the return flow from the fuel pressure regulator will only make it as far as the bottom of the petcock and never up into the tank where it can lose heat and bubbles.

But this doesn't mean that the idea is dead or won't work. It just needs to be looked at again. I think there's a good chance we can figure out a way to change the routing of the return fuel so it goes up the petcock's "On" tube and into the tank so it can lose heat and bubbles then return through the "Reserve" tube and out of the petcock and back to the fuel pump.

If this can be done the petcock will still work like a normal (for a fuel injection engine) petcock. You would be able to shut it off with the "Off" position, you would have normal fuel delivery with the "Reserve" position. The "On" postition would inoperative because its tube would be handling the fuel regulator return flow to the tank.

Now I know that some of you might think that losing one of the petcock settings is a bad thing or that it means a reduction of functionality in the petcock, but that's only because you're still thinking in carbed-engine mode. In a fuel injection system the "On" vs. "Reserve" just doesn't matter any more, and "Reserve" is the correct choice in this case to keep for the single available setting because it feeds from lower in the fuel tank.

The reason that "On" and "Reserve" don't mean the same the same thing for a FI engine vs. a carbed engine is that you can't run an FI engine dry at the "On" setting and then expect the FI system to regain its prime by just switching it to "Reserve". It's just not guarenteed to happen that way. If you've run the FI pump till it goes dry enough to cavitate on air, there's a good chance it won't re-prime just from gravity flow (this is highly dependent on where the pump is mounted in relation to the fuel tank) and there's also a chance the pump will damage itself in the process of cavitating. Not a good way to treat your fuel pump on a regular basis.

I run my system on "Reserve" all the time and simply take note of the trip odometer to know when to fuel up.

[greg737]

No, if I read his (="ecotron guy") info correctly, he returns fuel through the vent tube on the back of the tank. Normally this tube just vents the tank through a rubber hose to the bottom of the bike. So its a viable return port. He drills a hole near the filler cap for some reason that I have not figured out. I don't think he does anything with the petcock vacuum line.

I agree with you that this method of fuel return is just asking for trouble.

First, drilling a hole in the top of the tank without repainting the area where you've drilled (I assume most who might do this version of fuel return won't take the time to repaint around the newly drilled hole) is a bad idea because it will end up rusting.

Second, you've just opened up a potential path for water to enter the fuel tank. Remember, the reason that hard-line exists in the fuel tank's structure in the first place is to drain off water (and spilled fuel) that may end up in that area around the tank lid assembly. And now you're closing off that drain route for any water (and spilled fuel) that may end up in that area on a rainy day ride or parking situation. So now if water puddles in there it has nowhere to go. Except you've just drilled a new hole into the tank in this area for your return connection when you re-purposed the drain vent line. Yes, you've made an effort to make this new hole waterproof, but who knows?

[choneofakind]

Originally Posted by n4mwd

Yes that's what I meant. But if you have a fuel pump, why do you care about creating a vacuum in the tank? A lot of cars with FI are sealed and you can hear the vacuum break when you open the gas cap to refill it. Is it possibly because the pump on bike is not strong enough?

Normally what you hear when you take the gas cap off a car is the pressure release from expanding gas vapors, just like you hear when you open up the lid on the tank on the 250R. When your car gets e-checked every other year, the e-check people test that the cap can hold a certain amount of positive pressure before the safety release goes. That means they're expecting a positive pressure and not a vacuum. A vacuum would make the pump work harder and less effectively. My question is if they cap would allow enough air flow INTO the tank to allow the fuel return to be run into the breather port like in the instructions given with the kit.

For the petcock, what if we took metal plate the same dimensions as the base of the petcock and the same o-ring as the petcock, and ran two 5/16 inch brass nipples into it. Then attach a short length of fuel line and an on/off valve on both, effectively making our own fuel tap and fuel return?

[choneofakind]

Originally Posted by greg737

I agree with you that this method of fuel return is just asking for trouble.

Second, you've just opened up a potential path for water to enter the fuel tank. Remember, the reason that hard-line exists in the fuel tank's structure in the first place is to drain off water (and spilled fuel) that may end up in that area around the tank lid assembly. And now you're closing off that drain route for any water (and spilled fuel) that may end up in that area on a rainy day ride or parking situation. So any water that might puddle in there now has nowhere to go. Except you've just drilled a hole into the tank in this area for your return connection when you re-purposed the drain vent line. Yes, you've made an effort to make this new hole waterproof, but who knows?

what about the hole in the cap that some newgen owners drill to vent the gas cap better and get rid of the whistling from expanding gas vapors? would something like that work to get rid of the pressure difference? I haven't read about any of them complaining of water in the tank.

[greg737]

Think about this from a constant volume and constant pressure situation. The tank is a fixed volume and it will always get back to normal atmospheric pressure. Normally, the carbs pull vacuum and suck out gas. This creates a low pressure in the tank which is remedied by the breather. In the instructions I linked above, the return is routed through the breather and there is a hole drilled in the top of the tank because the breather is no longer adding air to compensate for all the gas leaving the tank, and even with fuel returning to the tank, there is still a net loss of matter in the tank's point of view. There has to be a way for air to get into the tank to neutralize that negetive pressure; hence the hole in the top. At least, that's what I've gotten from reading about this. Correct me if I'm wrong @greg737

It's a common misconception that the drain line that comes from the tank lid area has something to do with relieving the tank's vacuum. It does not. All the drain line does is remove water and spilled fuel that may end up in the area around the tank lid assembly.

The vacuum that develops in the EX-250's tank results (primarly) from the simple fact that as fuel is removed from the tank by the engine (as the level goes down) it exerts a negative pressure on the air/vapor volume above the fuel. Secondary vacuum (negative pressure) can result from cooling of the fuel and vapor volume in the tank, the same as heating of the fuel and vapor in the tank can create a positive pressure situation in the tank.

It's these conditions that can generate the EX-250 fuel tank "whistle" we're all familiar with.

These pressure differentials are dealt with not by the drain line but by valving and spring-tensioned seals in the bike's fuel tank lid (the part that swings up from the fuel filler hole when you refuel the bike). Take a close look at this part next time you have it open. If you look at it carefully you can see some of the spring-tensioned seals that are arranged to create both over-pressure and under-pressure relief.

[greg737]

what about the hole in the cap that some newgen owners drill to vent the gas cap better and get rid of the whistling from expanding gas vapors?

It's a pretty cave-man solution to a minor annoyance, isn't it?

would something like that work to get rid of the pressure difference?

The tank already has provisions for pressure differential equalization as I've described in my last post. Just because it whistles sometimes doesn't mean it's not a good solution. It was good enough for the Kawasaki engineers so it's good enough for me.

I haven't read about any of them complaining of water in the tank.

Maybe not, but I'm not drilling any new holes in the top of my fuel tank. I'm not going to bet against the effects of water+gravity+time.

[greg737]

Normally what you hear when you take the gas cap off a car is the pressure release from expanding gas vapors, just like you hear when you open up the lid on the tank on the 250R. When your car gets e-checked every other year, the e-check people test that the cap can hold a certain amount of positive pressure before the safety release goes. That means they're expecting a positive pressure and not a vacuum.

Not exactly. The reason they're only testing for positive pressure holding ability is they're the EPA. They're concerned with limiting fuel tank emissions, which would occur if the tank couldn't hold a certain amount of positive pressure. They couldn't care less about a vacuum (negative pressure) in the tank because it would only suck air into the tank wouldn't result in any emission of gasoline fumes.

[greg737]

For the petcock, what if we took metal plate the same dimensions as the base of the petcock and the same o-ring as the petcock, and ran two 5/16 inch brass nipples into it. Then attach a short length of fuel line and an on/off valve on both, effectively making our own fuel tap and fuel return?

I think you're right. I've been outside looking at my bike's petcock and it's so minimally cast that there's really no room for modification (without destroying it).

So modifying the OEM petcock is out. But I also believe that drilling holes anywhere in the fuel tank should be ruled out also.

I think that somewhere back in the "EFI KIT" thread there was somebody saying they'd found an aftermarket petcock that would fit the EX-250 and it had a simple "feed on one side - return line into the tank on the other side" design. That would be the best solution.

[n4mwd]

I too was thinking about the possibility of making a custom "fuel tap" to replace the petcock that would allow for fuel return. I don't see the need for a "petcock" at all. That is, why do you need to be able to shut it off on an FI bike? Worst case, get a secondary valve and put underneath it.

Anyhow, an aluminum plate with two tubes through it. And one capacitance probe for gas level. The gas level can be read by a single wire in the tank by checking its capacitance. This is how a lot of aircraft do it. This could turn on an indicator light warning of a low fuel situation.

An off the shelf solution would be ideal, but somehow I don't think its going to be exactly what you want.

Ok, thanks for clearing me up on the tank "Vent" tube which apparently is not really a vent tube at all. What about CA tanks? They have two "vent" tubes.

[greg737]

What about CA tanks? They have two "vent" tubes.

Yes, the CA bikes have an extra port into the fuel tank as part of the evaporative emission controls. If you had a CA bike and wanted to do a fuel injection project you'd be home-free.

I don't see the need for a "petcock" at all.

Believe me, you'll be wanting one when you have a maintenance task that requires you to remove the fuel tank from the bike.

[k12.usmc]

My ankle is fine. I fractured my cuboid and after looking at my CT scans, I would say more like pulverized. Also unless you are wearing high end racing boots, no boot is going to protect you from crushing forces. A good pair of boots should prevent road rash and keep your foot straight.