MPG - A total let down!

[Jpainter187]

For the past few months of owning my 2004 Rockster, I have ridden it whenever the weather permits... And after running some FI cleaner, and about 6 other tanks (give or take) of super premium through it, I began checking my mileage. What a dissapointment that was!

Factoring in the amount of fuel used up until my reserve light came on, I have been getting between 28-31 MPG. That's the same as my '99 323i when driing in the city!

What kind of mileage do you get from stop-n-go riding? Can someone please give me some guidance and a list of steps that should be taken to hopeully inscrese my Rocksters mileage?

[boxermania]

Seems a bit low.....two things:

Have the TB's been sync'd recently
Have the stick coils been checked

[Jpainter187]

The TBs have been synched as close as I could get them without a manometer. My dad has a mercury manometer than I plan to use as soon as I can locate it in his machine shop... And as soon as I get some guidance on where the vacuums are on the bike.

And no, the stick coils have not been checked. If this is something the dealership checks every 6k miles, then it has been about 7,500 miles ago.

[reidmct]

Factoring in the amount of fuel used up until my reserve light came on, I have been getting between 27-30 MPG. That's the same as my '99 323i when driing in the city!

Perhaps you are measuring fuel usage indirectly - and thereby introducing error.

Calculate mileage when you re-fill your fuel tank. Whether or not the reserve light is lit is irrelevant. Use the gallons figure shown on the pump. Use the miles shown on your trip meter. Reset the trip meter after you fill up.

[Jpainter187]

I've done that also. If I fill up right after the reserve light comes on I will put in 4.001 gallons, which is what the last receipt I have says. All my other receipts are far off from that.

[NoRRmad]

...And the miles on your trip odometer?

(I usually get about 45 MPG, generally highway miles, right at the speed limit.)

[Jpainter187]

I bieleve that fill up my trip meter read 116. But other times it has been 110, and the most it has ever been was 125.

[Lion_Lady]

Hmmm. What is your usual "cruising" RPM? When do you upshift?

Could be that you're running the bike at a higher RPM than will get you optimum gas mileage. Or you're hamfisted with the "fun stick." I''ve got a friend with a Rockster who rides pretty aggressively and gets mileage similar to yours (FWIW she has no windscreen on her Rock). For me, the low fuel light comes on at 145-155 miles on the odometer (depending on how full I fill the tank), and I usually get around 40-46 mpg.

I generally strive to run the bike between 3800 and 4200 around town. On the highway I'll usually run in 6th gear at 4500 or so (70+ mph).

P

[Jpainter187]

I shift anywhere between 3 and 5k RPM. I have to ride on the highway from one town to another to get to work so that's about the only time I use 6th gear, and I'll cruise at around 65 or 75, depending on speed limit. But highway riding is only about a 5 minute part of my commute. The rest is through town. So no, I'm not really aggresive when I ride. Although I do have the touring windscreen on and never ride without my side cases...

[NoRRmad]

My 45 MPG highway figure is with the Sport Screen, and side cases. I do keep a close eye on the fuel, and once I saw 57 MPG at altitude -- across the high plateau in Montana. Fuel light didn't come on 'til 200 miles. It could be the urban riding, which I almost never do, but I'd check around for a low-level fuel leak, perhaps a fine spray from the quick disconnects. Maybe you could rev it up briefly in your garage and smell for gas.

[Jpainter187]

I will definitely do that. The previous owner did say he put quick disconnects on the fuel lines...

[riceburner]

The TBs have been synched as close as I could get them without a manometer. My dad has a mercury manometer than I plan to use as soon as I can locate it in his machine shop... And as soon as I get some guidance on where the vacuums are on the bike.

And no, the stick coils have not been checked. If this is something the dealership checks every 6k miles, then it has been about 7,500 miles ago.

hang on.... you don't know where the vacuum pick up points are, and you've done TB synch??? How??

Get thee to a manometer my son, and get it done properly!

[NoRRmad]

I don't think a bad sync job would result in low fuel milage, but the engine will run smoother if you do it right...

Vacuum pickup points are on the bottoms of the throttle-bodies. there are small-diameter hoses leading to the vapor cannister. Remove these hoses and connect your manometer to the nipples. If you search for "throttle sync," there are writeups on the procedure here. Most use a simple water manometer, to avoid sucking mercury into the engine if the sync is way off.

[Jpainter187]

I adjusted them by lightly seating each TB screw then backing them out 1-1/2 turns. Then by carefully listening to the engine and feeling it's vibration I was able to get a smoother idle speed and less vibration on take off. This works until I can go to my dads machine shop and have him give me a hand adjusting them with his mercury manometer. My dad has ridden R bikes for about 20 years and done all of his own maintenance on them so I don't really see a need to buy one of the expensive manometers when this one has worked fine for him in the past.

[riceburner]

I adjusted them by lightly seating each TB screw then backing them out 1-1/2 turns. Then by carefully listening to the engine and feeling it's vibration I was able to get a smoother idle speed and less vibration on take off. This works until I can go to my dads machine shop and have him give me a hand adjusting them with his mercury manometer. My dad has ridden R bikes for about 20 years and done all of his own maintenance on them so I don't really see a need to buy one of the expensive manometers when this one has worked fine for him in the past.

A manometer is quite possibly the cheapest tool you can make!

check the forum for build threads - most here have made their own with ease.

[boxermania]

Jpainter187

Based on you latest post you didn't sync the TB's all you did was set/sync the idle speed. The TB's are sync at an engine speed of 2500 rpm too 3500 rpm to allow and measure air flow (or the vaccum created by air movement) past the throttle valves.

This is a very importatnt adjustment, as if they are off, one cylinder will be operating less efficiently than the other and therefore the good cylinder will have to carry the extra load, which results in poor mileage.

As suggested by riceburner get the TB's sync'd and keep us posted

[Jpainter187]

I'm going to try and get it done this weekend... That is, if all goes to plan.

[Jpainter187]

I went ahead and adjusted the valves before trying to synch the TBs. I lightly seated each brass screw then backed them out 1-1/2 turns before starting the bike. At first I got the idle spot on, then started equalizing them at 3,000 RPM. Once I got this within a half inch of one another I let it idle down. But now when idling one cylinder is always pulling a lot more than the other. Is it best to find a happy medium between idle speed and roughly 3,000 RPM? Or should I mainly worry about the synch at the higher rev and be done with it?

[NoRRmad]

The brass screws are for idle adjustment only. You then sync the high-RPM case using the right-side throttle-cable-adjust where the cables go into the throttle body. Be careful that the cables are fully seated into the ferules.

[Jpainter187]

I don't know how I forgo that. I watched the BMW tech video on how to do this a few months ago but clearly I wasn't paying enough attention...

I've got them synched as good as it gets with a homemade manometer. Idle speed is side-by-side and at 3,000 RPM they are within an inch of one another. Hopefully this will help increase my gas mileage. I am still going to try and check the QD fuel lines for any small leaks, but probably wont get to that until next weekend.