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very poor MPG

Posted: 08:33 pm Aug 20 2017
by Lumpy
really not sure why but single track trail riding is netting me an awesome 10 mpg at best . this is my first KDX and I am sure I should be getting at least double ' here are the particulars on my bike: 2000 KDX 200 , compression check cold is at 132PSI , carb completely rebuilt along with a new jet block gasket. slo jet is a 140 at 1 3/4 turn out , 152 main jet and a new CEL needle 3rd clip. . brand new boysen 607 power reeds. I did a plug chop on a 145 main and it was just slightly lean and did not have a 148 or a 150 so I threw in the 152 to be on the save side, I will be picking up a 148 and 150 to dial it in. fires up on the first or second kick reall easy. I ride Michigan single tracks and absolutely love the KDX and it has put a smile on my face beyond expectations. It carves through the wood and makes riding a dream . right now I am limited to trails loops under 22-25 miles. Hoping some one can give me some advise and help lead me in the right direction.

Re: very poor MPG

Posted: 09:40 pm Aug 20 2017
by John_S
Have you ever had the CEL on the 2nd or 1st clip? Last summer mine was rich with the CEL in anything but the 1st clip. A rich needle will guzzle gas. It could also be a float height or float valve issue. My brand new 35 carb was drinking gas so fast and I noticed a couple times when I stopped that it was just pouring out the overflow tube about as fast as it could. It had an intermittent sticky float valve. A new float valve and polishing the float valve seat finally fixed it. I was probably getting under 10mpg there for a while. It does pretty good on gas now even in deep sand and hard on the gas. The worst mpg I've seen this summer was flipping to reserve (from a full tank) at 47 miles but the sand was really soft.

Re: very poor MPG

Posted: 07:08 am Aug 21 2017
by John_S
Doing like the guy did in this video is what ended up fixing mine. I bought a new float valve but it might have worked just polishing it. I've done this on older carbs also and now use it as part of carb cleaning maintenance. It works great! Our float seat doesn't remove like his so you have to do it while it's still in the carb. Shoot some carb cleaner in and blow it out with compressed air afterwards.

The polishing starts at 1:12 in the video


Re: very poor MPG

Posted: 01:17 pm Aug 21 2017
by KDXGarage
Wow. He put a shine on it#

Re: very poor MPG

Posted: 01:44 pm Aug 21 2017
by JL4049
I had a similar issue when I first got mine. Float height was set wrong, the float needle was also sticking in its bore. Polished bore and reset floats which made a major improvement. I can get over 130km on a tank now in a mix of open fire trails and 2nd/3rd gear single.

Re: very poor MPG

Posted: 07:46 pm Aug 21 2017
by Vossman
JL4049 wrote:I had a similar issue when I first got mine. Float height was set wrong, the float needle was also sticking in its bore. Polished bore and reset floats which made a major improvement. I can get over 130km on a tank now in a mix of open fire trails and 2nd/3rd gear single.
This makes sense, you're probably spilling fuel out the overflow as you ride.