HELP! Getting poor fuel mileage
#31
My setup is quite similar to yours. I have an '09 250, I have a OEM KLX300 exhaust system with no butt plug, and I am not running any snorkle in the airbox cover. I drilled the slide and rejetted with Keihin jets: 122 main (118 was stock) and N1TC needle set to the second clip from the top (it might even be the top position, I don't remember). Left the stock 35 pilot jet. I don't have a pic, but after thousands of miles the insulator of my spark plug is just a nice tan color.
If anything, my bike runs a little on the lean side, but it still runs well in temperatures down into the 20's F. That said, I normally get 50-55 mpg on the highway (per bike odometer) running 60-70 mph indicated at 6500-7000 RPM or so. It drops a little when trail riding, but the lowest I know of was about 45 mpg.
With all the info you've given us so far, I'd say you need to check the clip position on the needle and swap that pilot jet back for the stock 35. Also, if you have the washer on the needle, it should normally go on top of the clip, not below it.
...And still do check the float height/fuel level in the carb.
If anything, my bike runs a little on the lean side, but it still runs well in temperatures down into the 20's F. That said, I normally get 50-55 mpg on the highway (per bike odometer) running 60-70 mph indicated at 6500-7000 RPM or so. It drops a little when trail riding, but the lowest I know of was about 45 mpg.
With all the info you've given us so far, I'd say you need to check the clip position on the needle and swap that pilot jet back for the stock 35. Also, if you have the washer on the needle, it should normally go on top of the clip, not below it.
...And still do check the float height/fuel level in the carb.
#32
Why not the static float height measurement? If that float isn't 100% in its buoyancy value...how well an object floats in liquid...it will yield a different fuel level. There is also a small amount of "stiction" in the float hinge, the float pin, the needle-and-seat, etc. that can influence the static height measurement of the float, yielding a slightly different actual fuel level once fuel saturates those parts. Bottom line is that the clear tube method guarantees what the true fuel level is in your carb.
#33
I have a 40 Pilot on mine, with a 331 big bore. I went up from the stock 35 in order to quieten a decel pop, which it helped. However, the 40 is too big, as I found an exhaust leak that I believe is causing the pop (the pop worsened as the leak increased in size). I'll be going back to 35 next time I take the carb off. I run a DJ132 Main jet.
I almost always get at least 50 mpg, sometimes more if I'm on powerline-type roads instead of single-track.
Yours was running rich...no doubt about it!
I almost always get at least 50 mpg, sometimes more if I'm on powerline-type roads instead of single-track.
Yours was running rich...no doubt about it!
#34
Ok, so here goes my float test. Let me know if I did it right or not. I tried it a couple times and kept getting the results in the 1st picture below. I only was getting fuel in the clear line to the bottom of the float bowl. I knew there was no way that was correct and had to think about what I was doing and what might be wrong. If you look closely at the picture you can see air between drain nipple and the bend in the clear hose. I didn't think that was right and flicked the clear hose with my finger some and shock it back and forth and the fuel rose to the point in the second picture where no air is visibl in the line. If I did this float test correctly then it appears my results show the float is spot on. Correct me if I am wrong or did something wrong here.
#35
Ok, so here goes my float test. Let me know if I did it right or not. I tried it a couple times and kept getting the results in the 1st picture below. I only was getting fuel in the clear line to the bottom of the float bowl. I knew there was no way that was correct and had to think about what I was doing and what might be wrong. If you look closely at the picture you can see air between drain nipple and the bend in the clear hose. I didn't think that was right and flicked the clear hose with my finger some and shock it back and forth and the fuel rose to the point in the second picture where no air is visibl in the line. If I did this float test correctly then it appears my results show the float is spot on. Correct me if I am wrong or did something wrong here.
#36
New air filter is on the way and I picked up a new plug today. So I will be able to eliminate a dirty filter once I get it back together and see how it runs.
#37
I am going to move on to focus on the jetting itself. First I want to pull the needle and make sure the clip was installed on the second from the top and not second from the bottom. If the clip is in the right slot, should I mess with it? Up of down? I think I am going to put the #35 pilot jet back in. I also ordered a new 118, 120, and 122 main jets. I think I am going to drop it down to a 122 while in there.
New air filter is on the way and I picked up a new plug today. So I will be able to eliminate a dirty filter once I get it back together and see how it runs.
New air filter is on the way and I picked up a new plug today. So I will be able to eliminate a dirty filter once I get it back together and see how it runs.
I think the stock pilot jet is the ticket.
On the needle position, just start playing with it one adjustment at a time. You can adjust the needle position without removing the carb. just pull the seat and tank and then you can access the top cover of the carb. It takes about 15 minutes to adjust the needle.
Ride the bike for a good long 15-20 minutes and note its characteristics, then adjust the needle up or down. Then go ride it again. Trust me, you will notice the differences. Seems like the 3rd clip is the sweet spot on most of our bikes, but some like the 2nd clip and some run better on the 4th clip.
#39
Landon-I'm not familiar with this particular bike (yet) but just wanted to offer some discussion concerning your problem. Your thread is really great and informative, but I think you'd rather be riding than offering a seminar on carb maintenance! Hang in there, it's bound to be simple (my vote is stock pilot). I've done a lot of street bike mods in the 40 years of riding, and it seems like your air box is still mostly in tact. Pilot should not need the change. I think your main and needle drilling should be more than enough to compensate for the increase in air flow.
Does the KX snorkel provide a bigger opening for the air box or is it in a different location than the stock snorkel? It seems like that is a popular mod done here (and on a lot of street bikes) but in some cases you may not be directing the air to the right spot. Judging by your photos of the UNI filter and spark plug, it almost looks like the filter is pluging with oil or fuel. To me it indicates lack of air. Is there fuel or oil in the oil box?
You may want to try a K&N OE size filter instead of the UNI. Just a better product IMO. UNI's strike me as lawn mower filters and react the same way to dirt.
If your latest effort doesn't help, I'd go back to stock jets, air box and a K&N filter. 2010 Kawasaki KLX250TAF (KLX250S) Parts, 2010 Kawasaki KLX250TAF (KLX250S) OEM Parts - BikeBandit.com check there for jet sizes. Maybe even trow the stock silencer back on and start over. I always found that silencer/air filter mods did let the bike breathe and rev better, but produced very little performance increase on a dyno. At least then you can ride more and wrench less. The stage one stuff (like this) should be basic with a stock box, high flow filter and moderate jetting changes undo what emissions trolls have wrought. Once you mod the air box, you may as well just get rid of it and go big bore as well. Gains are measured in $$$ at that point. Then at least the carbs are easier to get off the bike. Jetting is like suspension, Should only have to set it up once. I give you credit for catching the issue and not just trashing your bike. Alot of guys build so much stuff on an under powered bike they can't tell what's happening. Best of luck to you and keep us updated on your efforts!
Does the KX snorkel provide a bigger opening for the air box or is it in a different location than the stock snorkel? It seems like that is a popular mod done here (and on a lot of street bikes) but in some cases you may not be directing the air to the right spot. Judging by your photos of the UNI filter and spark plug, it almost looks like the filter is pluging with oil or fuel. To me it indicates lack of air. Is there fuel or oil in the oil box?
You may want to try a K&N OE size filter instead of the UNI. Just a better product IMO. UNI's strike me as lawn mower filters and react the same way to dirt.
If your latest effort doesn't help, I'd go back to stock jets, air box and a K&N filter. 2010 Kawasaki KLX250TAF (KLX250S) Parts, 2010 Kawasaki KLX250TAF (KLX250S) OEM Parts - BikeBandit.com check there for jet sizes. Maybe even trow the stock silencer back on and start over. I always found that silencer/air filter mods did let the bike breathe and rev better, but produced very little performance increase on a dyno. At least then you can ride more and wrench less. The stage one stuff (like this) should be basic with a stock box, high flow filter and moderate jetting changes undo what emissions trolls have wrought. Once you mod the air box, you may as well just get rid of it and go big bore as well. Gains are measured in $$$ at that point. Then at least the carbs are easier to get off the bike. Jetting is like suspension, Should only have to set it up once. I give you credit for catching the issue and not just trashing your bike. Alot of guys build so much stuff on an under powered bike they can't tell what's happening. Best of luck to you and keep us updated on your efforts!
Last edited by brooksie; 01-07-2012 at 01:55 AM.
#40
Landon-I'm not familiar with this particular bike (yet) but just wanted to offer some discussion concerning your problem. Your thread is really great and informative, but I think you'd rather be riding than offering a seminar on carb maintenance! Hang in there, it's bound to be simple (my vote is stock pilot). I've done a lot of street bike mods in the 40 years of riding, and it seems like your air box is still mostly in tact. Pilot should not need the change. I think your main and needle drilling should be more than enough to compensate for the increase in air flow.
Does the KX snorkel provide a bigger opening for the air box or is it in a different location than the stock snorkel? It seems like that is a popular mod done here (and on a lot of street bikes) but in some cases you may not be directing the air to the right spot. Judging by your photos of the UNI filter and spark plug, it almost looks like the filter is pluging with oil or fuel. To me it indicates lack of air. Is there fuel or oil in the oil box?
You may want to try a K&N OE size filter instead of the UNI. Just a better product IMO. UNI's strike me as lawn mower filters and react the same way to dirt.
If your latest effort doesn't help, I'd go back to stock jets, air box and a K&N filter. 2010 Kawasaki KLX250TAF (KLX250S) Parts, 2010 Kawasaki KLX250TAF (KLX250S) OEM Parts - BikeBandit.com check there for jet sizes. Maybe even trow the stock silencer back on and start over. I always found that silencer/air filter mods did let the bike breathe and rev better, but produced very little performance increase on a dyno. At least then you can ride more and wrench less. The stage one stuff (like this) should be basic with a stock box, high flow filter and moderate jetting changes undo what emissions trolls have wrought. Once you mod the air box, you may as well just get rid of it and go big bore as well. Gains are measured in $$$ at that point. Then at least the carbs are easier to get off the bike. Jetting is like suspension, Should only have to set it up once. I give you credit for catching the issue and not just trashing your bike. Alot of guys build so much stuff on an under powered bike they can't tell what's happening. Best of luck to you and keep us updated on your efforts!
Does the KX snorkel provide a bigger opening for the air box or is it in a different location than the stock snorkel? It seems like that is a popular mod done here (and on a lot of street bikes) but in some cases you may not be directing the air to the right spot. Judging by your photos of the UNI filter and spark plug, it almost looks like the filter is pluging with oil or fuel. To me it indicates lack of air. Is there fuel or oil in the oil box?
You may want to try a K&N OE size filter instead of the UNI. Just a better product IMO. UNI's strike me as lawn mower filters and react the same way to dirt.
If your latest effort doesn't help, I'd go back to stock jets, air box and a K&N filter. 2010 Kawasaki KLX250TAF (KLX250S) Parts, 2010 Kawasaki KLX250TAF (KLX250S) OEM Parts - BikeBandit.com check there for jet sizes. Maybe even trow the stock silencer back on and start over. I always found that silencer/air filter mods did let the bike breathe and rev better, but produced very little performance increase on a dyno. At least then you can ride more and wrench less. The stage one stuff (like this) should be basic with a stock box, high flow filter and moderate jetting changes undo what emissions trolls have wrought. Once you mod the air box, you may as well just get rid of it and go big bore as well. Gains are measured in $$$ at that point. Then at least the carbs are easier to get off the bike. Jetting is like suspension, Should only have to set it up once. I give you credit for catching the issue and not just trashing your bike. Alot of guys build so much stuff on an under powered bike they can't tell what's happening. Best of luck to you and keep us updated on your efforts!
At this point with my work schedule I won't be wrenching on the bike anymore till next Thursday. Once I get back at it I think my first step is going to be pull the head cover and check the valve clearance. If one of them is out of wack for some reason any jetting I do may not help. So I want to check them before I continue. Then I will pull the N1TC needle and confirm the clip is in the correct slot 2. Then I am going to put a #35 (stock) pilot back in and drop the main jet from the 125 to 122. Install new air filter and plug, reassemble bike and take it for a spin and see how she runs and performs.