Why the sucky gas mileage?

Gbug · March 16th, 2009, 11:20 PM

I'm running the stock exhaust, desnorkled, needles shimmed with one 4mm washer. For about the last 5 or 6 tanks, I'm only getting about 35 mpg. Sometimes a couple better/worse. I usually cruise on the highway at about an indicated 80mph. I'm geared +1, so that usually puts me at about 8-9k rpms. City driving is not really any better. In the city, I cruise anywhere from 5-8k rpm, and don't redline very often. I guess I can accept 45 mpg, but 35? It's a 250 for crying out loud! What gives?

Verus Cidere · March 16th, 2009, 11:26 PM

Mine did that to me for a little while too. Don't quote me on this, 'cause I'm definitely not an expert, but you might try going a little bit lower in RPMs inside the city. There's not many places in my city where the speed limit goes above 45 mph. You should be able to hit that in 6th without going past 6k. I'd suggest getting up to 6th as soon as possible after getting going and staying there as long as possible. Also, don't keep the gas held for very long if you're coming up to a red light or stop sign. The longer you hold it, the more you use. I can't say for sure that's what was going on with mine, but I did notice a difference in gas mileage after trying the lower RPM trick (aka went from 40 to 55). Try it out.

Alex · March 16th, 2009, 11:27 PM

I've gotten as low as 33 mpg for a tank, but that's a tank that has been held at full throttle and high revs for the vast majority of the tank. With the usage you've described, I'd expect 40-45 on my bike, and I think I'm on the low end for fuel efficiency. Did you used to get significantly better mileage? Can you think of anything that may have changed that could be a contributing factor? How are you calculating your fuel mileage?

kkim · March 16th, 2009, 11:28 PM

how are you calculating your gas mileage?

Nemy · March 17th, 2009, 09:44 AM

and how many clicks do you have on the bike? There've been reports that the ninjette doesn't have the best mileage during its early stages of life.

OldGuy · March 17th, 2009, 10:16 AM

Quote:

Originally Posted by Nemy

There've been reports that the ninjette doesn't have the best mileage during its early stages of life.

I may have a "non-conforming" Ninja but my first fill up yesterday after only 152 miles gave me 54.5 mpg. 25 of the first 50 miles were out on back roads varying the speed/rpm in all gears but never exceeding 6K or 55 mph. Rest of the miles are on my daily commute in town 8 miles each way.

Gbug · March 17th, 2009, 10:28 AM

How I calculate: Fill gas tank to full, reset trip. Next time I fill up to full, divide miles on trip by amount of gas I just put in.

Its an '08 with 7k miles on it. I bought the bike used, and only had it for a short while before I shimmed the needles. I think I got about 55 mpg before shimming. I started out with two washers per needle, but it bogged when I got above 10k rpm, so I cut it back to one per needle. Now it pulls great up to redline, so I don't think it's running rich. I went with 4mm washers cause I couldn't find 3mm ones anywhere. I don't think the 1mm difference is the problem though.

One other thing that might be the culprit. I noticed when I removed the washers that I had a slight tear around the edge of one of the rubber diaghram things that covers the carb. Is it possible that this could be jacking with my gas mileage?

kkim · March 17th, 2009, 11:05 AM

Quote:

Originally Posted by Gbug

One other thing that might be the culprit. I noticed when I removed the washers that I had a slight tear around the edge of one of the rubber diaghram things that covers the carb. Is it possible that this could be jacking with my gas mileage?

That may have some bearing on the problem. how bad is the tear? they can be repaired, you know.

Gbug · March 17th, 2009, 05:32 PM

Hmmm, how would I go about repairing it? I checked and its about $35 for a new one.

kkim · March 17th, 2009, 05:44 PM

Quote:

Originally Posted by Gbug

Hmmm, how would I go about repairing it? I checked and its about $35 for a new one.

I've heard it's more like a hundred.

where is it $35?

Use a vinyl rubber repair kit like they have to repair tire tubes. You'll need a relatively light pice of rubber/vinyl to use as a patch.

For more info, PM member TheDuck as he is the only one I know of that has repaired a torn diaphragm.

Picture of the tear before you patch it once you're in there?

Gbug · March 17th, 2009, 06:05 PM

Crap, I just double checked and its definetely about $100. I'll probably just try to repair it when I ever get around to it. And I'll be sure to snap a pic.

March 16th, 2009, 11:20 PM	#1
Gbug ninjette.org member Name: Grant Location: Waco Join Date: Jan 2009 Motorcycle(s): 2008 Ninja 250r Posts: 26	Why the sucky gas mileage? I'm running the stock exhaust, desnorkled, needles shimmed with one 4mm washer. For about the last 5 or 6 tanks, I'm only getting about 35 mpg. Sometimes a couple better/worse. I usually cruise on the highway at about an indicated 80mph. I'm geared +1, so that usually puts me at about 8-9k rpms. City driving is not really any better. In the city, I cruise anywhere from 5-8k rpm, and don't redline very often. I guess I can accept 45 mpg, but 35? It's a 250 for crying out loud! What gives?

March 16th, 2009, 11:27 PM	#3
Alex ninjette.org dude Name: 1 guess :-) Location: SF Bay Area Join Date: Jun 2008 Motorcycle(s): '13 Ninja 300 (white, the fastest color!), '13 R1200RT, '14 CRF250L, '12 TT-R125LE Posts: Too much. Blog Entries: 7	I've gotten as low as 33 mpg for a tank, but that's a tank that has been held at full throttle and high revs for the vast majority of the tank. With the usage you've described, I'd expect 40-45 on my bike, and I think I'm on the low end for fuel efficiency. Did you used to get significantly better mileage? Can you think of anything that may have changed that could be a contributing factor? How are you calculating your fuel mileage? __________________________________________________ Montgomery Street Motorcycle Club / cal24.com / crf250l.org / ninjette.org ninjette.org Terms of Service Shopping for motorcycle parts or equipment? Come here first. The friendliest Ninja 250R/300/400 forum on the internet! (especially Unregistered)

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March 16th, 2009, 11:26 PM	#2
Verus Cidere ninjette.org certified postwhore Name: Michael Location: Southern NM Join Date: Feb 2009 Motorcycle(s): '91 Honda CBR600 F2 Posts: A lot.	Mine did that to me for a little while too. Don't quote me on this, 'cause I'm definitely not an expert, but you might try going a little bit lower in RPMs inside the city. There's not many places in my city where the speed limit goes above 45 mph. You should be able to hit that in 6th without going past 6k. I'd suggest getting up to 6th as soon as possible after getting going and staying there as long as possible. Also, don't keep the gas held for very long if you're coming up to a red light or stop sign. The longer you hold it, the more you use. I can't say for sure that's what was going on with mine, but I did notice a difference in gas mileage after trying the lower RPM trick (aka went from 40 to 55). Try it out.

March 16th, 2009, 11:28 PM	#4
kkim Join Date: Nov 2008 Posts: Too much.	how are you calculating your gas mileage?

March 17th, 2009, 09:44 AM	#5
Nemy ninjette.org sage Name: Tim Location: Portland, OR Join Date: Dec 2008 Motorcycle(s): 2009 SE Ninja 250R Posts: 796	and how many clicks do you have on the bike? There've been reports that the ninjette doesn't have the best mileage during its early stages of life.

March 17th, 2009, 10:28 AM	#7
Gbug ninjette.org member Name: Grant Location: Waco Join Date: Jan 2009 Motorcycle(s): 2008 Ninja 250r Posts: 26	How I calculate: Fill gas tank to full, reset trip. Next time I fill up to full, divide miles on trip by amount of gas I just put in. Its an '08 with 7k miles on it. I bought the bike used, and only had it for a short while before I shimmed the needles. I think I got about 55 mpg before shimming. I started out with two washers per needle, but it bogged when I got above 10k rpm, so I cut it back to one per needle. Now it pulls great up to redline, so I don't think it's running rich. I went with 4mm washers cause I couldn't find 3mm ones anywhere. I don't think the 1mm difference is the problem though. One other thing that might be the culprit. I noticed when I removed the washers that I had a slight tear around the edge of one of the rubber diaghram things that covers the carb. Is it possible that this could be jacking with my gas mileage?

March 17th, 2009, 05:32 PM	#9
Gbug ninjette.org member Name: Grant Location: Waco Join Date: Jan 2009 Motorcycle(s): 2008 Ninja 250r Posts: 26	Hmmm, how would I go about repairing it? I checked and its about $35 for a new one.

March 17th, 2009, 06:05 PM	#11
Gbug ninjette.org member Name: Grant Location: Waco Join Date: Jan 2009 Motorcycle(s): 2008 Ninja 250r Posts: 26	Crap, I just double checked and its definetely about $100. I'll probably just try to repair it when I ever get around to it. And I'll be sure to snap a pic.