Bad Gas Mileage - Help!


27 replies to this topic
  • rkwfxd1

Posted December 09, 2009 - 09:44 PM

#21

I think one of the problems with our bikes is the fact that there is so much fuel BELOW the petcock. The petcock is like in the middle of the tank. I guess it is good to have a deep reserve but how do you get the fuel that is below the petcock back up to it to burn?

This problem is nicely solved with the Clarke and IMS tanks and the petcock is at the bottom of the tank where it belongs.

I wonder if these companies paid Yamaha to put the stock petcock where it is. I am pretty sure that if the stock petcock was on the lower left front corner of the stock tank like it should be I would never have found it necessary to buy the Clarke.

  • themaskcabana

Posted December 10, 2009 - 08:35 AM

#22

I am in the same boat here on the fuel consumption...er I mean GUZZLING. I gots an 08 WR450 with AIS removed, GYTR needle clipped 4th, 168 main, 48 pilot, grey wire cut, pipe insert and air boot removed, stock tank, Tusk fuel screw 1 1/2 turns out.

I get about 42-48 miles on a tank riding Dove Springs/Red Rock areas before going to reserve. At bone stock I would get about 60-65 miles.

My buddy's 07 with all same mods, except his has a Q4 pipe, was getting same miles (60-65) as me when I was bone stock. Now with my mods I am even more worse off!!

Everyone else with YZs and even a CRF150 don't even go to reserve like I have to on rides. AND they ride around more than I do from here to there while on these rides.

How and will sprocket changes effect my fuel mileage? From what I am reading, I need to stay in a higher gear and go easy on the throttle as much as possible right?

Definitely going to get a clarke tank though.


Well, I will keep you updated. I am in the middle of talking to JD from www.jdjetting.com (pluging his website since he provides awesome customer service) to figure out what the problem is. He's been "exceptionally" helpful and patient.

So far I found out that my "float bowl" needed adjustment (losing gas out of the overflow), and that my idol goes up when I screw my fuel screw all the way in. This suggests I have to big of a pilot jet, which is weird because I have a stock pilot jet (45) and with all my mods I would think I would need to go up in the pilot, but apparently not.

If I were you, you might want to check your pilot jet. Warm you bike up for about 10 minutes, and then turn your fuel screw in. If you can go all the way in and all that happens is the idle goes up, then you’re pilot jet is too big. It should start to cut out or stall because you are leaning it out. They say it should be between 1 and 2 turns out for a nice idle. You might want to check your float bowl too. If you are losing gas at all out of your overflow then you probably need to adjust that as well.

I’ll let you know what happens…

  • Butta

Posted December 10, 2009 - 09:31 AM

#23

In relatively stock form (grey wire mod, airbox restriction removed), I was averaging 50 mpg on a high mountain ride in Colorado (over 800 miles round trip). My riding partner had an '07 KTM 450 EXC and we were consistently filling up with the EXACT amount of fuel at every stop....right down to the tenth's of a gallon. My '05 WR450 has the Acerbis tank, and one leg we did was 145 miles....still didn't hit reserve on her.

Since that ride, I've removed the AIS, put on a YZ pipe, added a PowerNow+, and rejetted accordingly....I'm not sure what this will do to mpg, but if it gets too terribly bad, I may have 2 setups to use....a single track/short run setup (max power, bad fuel range), and a more mild but longer range (closer to stock) setup.

I really don't expect to see that much difference, but I'm sure with all the new found power my right hand will see more activity....that alone should drop my mpg's to the mid 30's.

  • Timo2824

Posted December 10, 2009 - 03:17 PM

#24

You should try leaning your needle out by raising the clip and dropping the needle one position. The bog, or stutter around 3/4 throttle you mentioned in your first post plus the black plug tells me your needle is probably rich. I had the same bog and black plug problem on my WR250F, and ended up having to buy a leaner needle with a different tapper to get rid of it. My bike also came with to rich of a pilot and main jet even after the free mods, and I'm only at 1100ft (335m) elevation. As a side note, I weigh 160 lbs without gear, race intermediate HS, and I can go over 50 miles without reserve on the stock tank.:banghead: In fact I have never even used reserve, when we trail ride we usually fill up at the 50 mile mark due to some 2-stoke riders.

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  • WR450FGreg

Posted December 11, 2009 - 12:30 PM

#25

.

my idol goes up when I screw my fuel screw all the way in. This suggests I have to big of a pilot jet, which is weird because I have a stock pilot jet (45) and with all my mods I would think I would need to go up in the pilot, but apparently not.


Yep, I've modified mine quite a bit too and it does exactly the same (ie idle high when the fuel screw is screwed right in) and that's why I'm ready to buy a smaller pilot jet for it.

I agree, it's weird that you'd need a smaller pilot jet since it's breathing so much more openly and (I assume) needing to suck more fuel to compensate for that "lung expansion".

Glad to hear someone else has the same issues/thoughts! :banghead:

Greg

  • oldmanx

Posted December 13, 2009 - 07:29 AM

#26

X2 on what TIMO says concerning the needle. I recently bought a 400MXC that's plated. Riding at partial throttle...25-40mph...the bike stuttered terribly. The back fender would get soot covered from exhaust and the plug was rich black. Raising the needle clip 2 places dropped the needle enough to clear up this issue. Fuel mileage increased accordingly.

  • themaskcabana

Posted December 14, 2009 - 10:52 AM

#27

.


Yep, I've modified mine quite a bit too and it does exactly the same (ie idle high when the fuel screw is screwed right in) and that's why I'm ready to buy a smaller pilot jet for it.

I agree, it's weird that you'd need a smaller pilot jet since it's breathing so much more openly and (I assume) needing to suck more fuel to compensate for that "lung expansion".

Glad to hear someone else has the same issues/thoughts! :moon:

Greg



Yep! I'm starting to learn that every bike is a little different. There's no cookie cutter pattern here, but I tell you that JD from JD jetting has help me significantly. I haven't had a chance to ride it, but I think everything is lined up. Hopefully, when I do ride my gas mileage goes up, I will keep everyone updated.

This is what I found out with the help of JD. First, he had me check my float bowl setting, and I found out it was off a little. I adjusted it and then he had me re-route my over flow tube so it wouldn’t leak gas if I was riding some steep stuff. Then he had me check my pilot screw, and I found out it was too big so I went to a 42, and now if I go in with the fuel screw it starts to cut out. I have it at about 1 turn out. My main is good, I think. Then I went to a 50 instead of a 40 on the leak jet. It seems to run good, but I won’t know for sure until I get some riding in.

I’ll keep everyone updated.

Thanks for all the info!

  • themaskcabana

Posted December 14, 2009 - 10:53 AM

#28

You should try leaning your needle out by raising the clip and dropping the needle one position. The bog, or stutter around 3/4 throttle you mentioned in your first post plus the black plug tells me your needle is probably rich. I had the same bog and black plug problem on my WR250F, and ended up having to buy a leaner needle with a different tapper to get rid of it. My bike also came with to rich of a pilot and main jet even after the free mods, and I'm only at 1100ft (335m) elevation. As a side note, I weigh 160 lbs without gear, race intermediate HS, and I can go over 50 miles without reserve on the stock tank.:moon: In fact I have never even used reserve, when we trail ride we usually fill up at the 50 mile mark due to some 2-stoke riders.


If it doesn't ride well after all the adjustments that I have made, this will be my next step. Thanks for the info. : )




 
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