Hi, new 919 owner and new to this forum. I have had my bike for two weeks and about 1,000 miles. My first two tanks of fuel were over 45 mpg. After that, mileage has dropped to mid to upper 30's...that's it. Even riding very gently. I have noticed that it falters, for lack of a better description at steady throttle position. I shrugged it off at first assuming that it was just pilot error as I was still getting used to my first EFI motorcycle. But I am now certain that something isn't right. When I first got it, it didn't idle very smoothly. I knew that the previous owner almost never rode it and that it likely had old, bad gas in it. I ran a couple of tanks with "Seafoam" in the fuel. It now idles almost perfectly and pulls nicely, but at steady throttle settings, feels like a miss. When I pull up to a stop, it really smells rich. I have a factory service manual. I intend to peruse it for clues as well as looking through posts online. I'm used to doing my own work, but have no experience with EFI. If I need to take it to a pro, I will.
Thanx! I have checked the air filter. The fuel pressure regulator explanation sounds quite plausible. I wonder if due to the age of the bike that I have brittle vacuum lines. I'll check it out.
Did you do any work on the bike before it started the problem? A few others have knocked loose a wire on a coil or something while the tank was up. If you haven't my money is on the FPR.
I've done virtually nothing so far. I've not had the tank up. I had trouble starting it recently and discovered that the battery cables were loose. I rectified that and other than chain maintenance and some new tires I haven't touched a thing. For that matter, I don't think that anyone else had for a while other than an oil change. The bike had 5,400 miles when I got it two weeks ago and I just turned 6,000 miles.
My 919 gets between 38-45 miles per gallon very routinely. I've gotten it down below 36 a few times, but that was due to too many fast starts from stoplights.
What RPM range are you at when the bike feels like it's missing? the stock 919s have alsobeen known to burble or even backfire a little bit on deceleration.
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Hi and thank you for all the great responses. I am running between 3,000 and 4,000 RPM when the symptom occurs. I have never felt what I would call a burble or a backfire on deceleration. This only happens at a steady speed. It did idle rough when I first got it, but that seems to be clearing up.
I wonder if due to the age of the bike that I have brittle vacuum lines. I'll check it out.
In my experience, which may be wrong, but an issue with vacuum lines usually cause backfire on decel, which you don't have, so I would not go to this first. My first inclination would be to check the spark plugs.
I raised the tank last night for a first look. The hoses that I felt of were still soft and supple. I just ordered a new air filter and I will pick up some plugs today. I am also going to speak with a pro who was with a Honda dealer for some twenty years. He knows and likes these bikes. Depending on what I learn, I may just let him have a session with it. I'm used to doing my own work, but this EFI is a different animal for me.
Have you pulled the plugs yet? I believe that from the factory, the Fuel Pressure Regulator (FPR) uses cylinders 2 and 3 (Center two) for pulling it's vacuum. So, if the middle two are starting to foul and the outer two look fine, that's probably your problem. Also, there is a vacuum line attached that you can pull. If it smells like fuel or has fuel running out of it, you need to replace the FPR.
I had a miss problem that was sporadic once. Ended up that one wire feeding a coil was broken inside the insulation. With only 6,000 on the clock, I can't see someone being in there enough to break something, but you never know.
Great responses! I'm loving this forum. I haven't pulled the plugs yet, but thanks for the heads up about cyls, 2&3. I'll keep that in mind.
See LDH's response.
LDH has done lots of mapping on the 919s.
His version 4 of his Moriwaki based tuning is the definitive map in my opinion.
Mine was dyno'd and remapped at 3500 ft altitude against his sea level dyno work, and what I ended up with a little different.
I printed out LDH's map, and colour keyed it show where it was richer that stock or leaner than stock. In the low RPMs and low throttle opening zone of the overall map, the general need is leaner by varying degrees, but richer in some zones. When you see such a map, you realize how poor the factory map is.
If you want to see what the colour keyed map looks like, send me a PM with an e mail address you have that can accept PDF file attachments, and I'll send it to you. I'd post it here, but I don't know how.
I had a similar issue and it turned out my battery wasn't providing enough juice. replaced the battery and problem solved, something about the ignition system if the battery is worn out it won't run right. judging from your loose cable Id take a multimeter to your battery and see whats going on when its running...
I just changed the spark plugs. They were all black and sooty, #2 and #3 were dripping wet. Where do I get a fuel pressure regulator? Is that a dealer part or do some of the other vendors have them?
Does that bike have a Powercommander or other Fi altering device installed?
FPR's go bad, but it is rare nowdays... If the bike had been neglected and sat for awhile you can get lots of crude in the injectors that keep them from closing completely when the bike is at rest. This can allow fuel to drip into the cylinders and in extreme cases it can actually fill the cylinders (this happened to me a couple months ago) all the way to the top of the throttle bodies. If you try to start the bike with the cylinders filled with liquid it can actually bend con-rods.
Someone straighten me out if I'm wrong, I'm an amateur trying to figure this stuff out. It looks to me that during low demand, there is greater vacuum and the regulator allows excess fuel to return to the tank. When the throttle is opened for higher demand, the regulator closes thus increasing the fuel supply available. If there is a vacuum leak it would operate as if there were high demand for fuel. The increased pressure in the rail causes excess fuel to force it's way through the injectors creating an excessively rich mixture. Could ethanol in the fuel cause the regulator to fail?
Someone straighten me out if I'm wrong, I'm an amateur trying to figure this stuff out. It looks to me that during low demand, there is greater vacuum and the regulator allows excess fuel to return to the tank. When the throttle is opened for higher demand, the regulator closes thus increasing the fuel supply available. If there is a vacuum leak it would operate as if there were high demand for fuel. The increased pressure in the rail causes excess fuel to force it's way through the injectors creating an excessively rich mixture. Could ethanol in the fuel cause the regulator to fail?
Not quite.
Assuming all components are in OK condition ,what actually occurs is this:
The ECU, on the basis of a RPM X Throttle Position co-ordinate map, instructs the injectors to open for a certain duration. This controls the volume of fuel metered by the injectors. (The ECU is continually reading the RPMs and the Throttle Positioner % of opening.)
The ECU relies upon the basic map, and then continually adjusts the map on the basis of continuous sampling from the related sensors. The ECU makes these map adjustments on the basis of Absolute Air Pressure, Intake Air Temperature, and Coolant Temperature. The map adjustments that the ECU makes will vary from richer to leaner overall, and does this by simply changing the duration that the injectors are instructed to be open. Fuel Rail pressure is not manipulated with this system, and is intended to be a constant.
Ethanol within Honda's allowable limit in gasoline, 10% to be exact, should not cause any problems to any of the components. Methanol is restricted to 5 % re blended into pump gasoline. Methanol needs co-solvents to stay in solution with the gasoline, and the co-solvents used can be bad for the synthetic rubber ("elastomer material") parts. Methanol blended gasoline also needs corrosion inhibitors, so if they are lacking, metal parts can be affected.
No, I spoke with the previous owner and he assured me that nothing like that has been done to the bike. I'm satisfied (at least for the moment) that the FPR is the culprit. When I first got the bike, I took it on a 300 mile ride. I got 48 mpg on the first tank and 45 mpg on the second. After that it dropped to 36 mpg and hasn't gotten any better. I didn't notice the rich smell until I started getting lousy mileage. I have put another 700 miles and haven't gotten over 37 mpg, and I have ridden it very gently in an effort to get better mileage. The previous owner told me that he always got mileage in the mid forties.
Quote:
Originally Posted by Lord Duckhunter
Does that bike have a Powercommander or other Fi altering device installed?
FPR's go bad, but it is rare nowdays... If the bike had been neglected and sat for awhile you can get lots of crude in the injectors that keep them from closing completely when the bike is at rest. This can allow fuel to drip into the cylinders and in extreme cases it can actually fill the cylinders (this happened to me a couple months ago) all the way to the top of the throttle bodies. If you try to start the bike with the cylinders filled with liquid it can actually bend con-rods.
I just changed the spark plugs. They were all black and sooty, #2 and #3 were dripping wet. Where do I get a fuel pressure regulator? Is that a dealer part or do some of the other vendors have them?
2 & 3 dripping wet suggests a failed FPR in involved, seeing as the FPR relies on vacuum from 2 & 3
I just changed the spark plugs. They were all black and sooty, #2 and #3 were dripping wet. Where do I get a fuel pressure regulator? Is that a dealer part or do some of the other vendors have them?
If you go to the link cmurphy pointed to "Fouled plugs yet again" it explains a simple test if you have a MightVac or some other means to create a vacuum on the line to the regulator.
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Okay, I'm just waiting for parts now. I'm not riding the bike until I get it fixed. I figure that I should go ahead and change the oil as it might have gas in it. I've got my fingers crossed that this will do the trick. Mcromo has me thinking about the Power Commander in the future. I just put tires on it and I recently did a top end job on my dirt bike so I need to catch my breath a little before I pull the trigger on that.
I want to thank everyone again for the great responses. My new FPR came in yesterday. I got it installed today. I noticed when I first started it that it seemed to want for me to keep the "choke" on a little longer. It also just sounded and felt a little different for lack of better description. I rode about 100 miles today. Stopped and checked mileage and 48.3 MPG! I didn't notice any smell either. This is a big relief. I'm looking forward to enjoying my bike now that he weather is cooling off a bit. I have also changed my oil and filter, spark plugs and air filter.
48 mpg! Ive never got anywhere near that! crack the throttle on that biaotch!!!!
I'd have to go digging, but there have been at least two threads on fuel economy. It seems the average is anywhere from 35 - 45 mpg. I'd say how much you crack the throttle is the major factor. I know I got better MPGs when I'd cruise the twisty stuff in 6th at 3,000 versus 3rd or 4th at 6,000.
I want to thank everyone again for the great responses. My new FPR came in yesterday. I got it installed today. I noticed when I first started it that it seemed to want for me to keep the "choke" on a little longer. It also just sounded and felt a little different for lack of better description. I rode about 100 miles today. Stopped and checked mileage and 48.3 MPG! I didn't notice any smell either. This is a big relief. I'm looking forward to enjoying my bike now that he weather is cooling off a bit. I have also changed my oil and filter, spark plugs and air filter.
My new FPR came in yesterday. I got it installed today. I noticed when I first started it that it seemed to want for me to keep the "choke" on a little longer. It also just sounded and felt a little different for lack of better description. I rode about 100 miles today. Stopped and checked mileage and 48.3 MPG! 
I didn't notice any smell either. This is a big relief. I'm looking forward to enjoying my bike now that he weather is cooling off a bit. 
I have also changed my oil and filter, spark plugs and air filter.
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