Two Stroke Motocross

Two Stroke Motocross Forum => Technical => Topic started by: 2005yz250 on April 02, 2012, 10:27:16 PM

Title: Is this too lean?
Post by: 2005yz250 on April 02, 2012, 10:27:16 PM

Hello once again I have to tune my bike to get better and better response ( go figure).  Right now i run a 178 main with a 50 pilot, air screw 1 turn out with a stock pipe and pro circuit long silencer.  My elevation is 550 ft and the average humidity is 80%.  My question is, would going to a 175 main and a 48 pilot be too lean?  I put them in and can definitely feel the difference in throttle response around the yard, but im afraid when I am out pinning it on the track the bike will be too lean? Is this true or am I just being too cautious? I just want some more response without burning up the bike.

Title: Is this too lean?
Post by: SachsGS on April 03, 2012, 12:50:16 AM

Post pictures of your sparkplug with the various jetting specs.

Title: Is this too lean?
Post by: 2005yz250 on April 03, 2012, 01:02:31 AM

Will do when I get the chance.

Title: Is this too lean?
Post by: eprovenzano on April 03, 2012, 01:01:43 PM

what's the reason for the change?  Does your bike bog, or is unresponsive somewhere in the RPM range?  Is the plug black, tan or white.  These are the things to consider when making jetting changes.  Post a pic of the plug as that will help us answer the question.

Title: Is this too lean?
Post by: metal_miracle on April 03, 2012, 05:46:59 PM

often you can feel the bike dies on wide open throttle

if its to lean on the main jet

Title: Is this too lean?
Post by: 2005yz250 on April 03, 2012, 11:54:19 PM

I find it to be just a little too sloppy from like 1/8 to 1/4 throttle.

Title: Is this too lean?
Post by: metal_miracle on April 04, 2012, 12:04:26 AM

think i would have hold throttle

just above idle and adjust the air screw out until it raises in rpm  then back just a bit

sine you air screw seem far in

Title: Is this too lean?
Post by: LukeDuke25 on April 10, 2012, 01:37:15 PM

Do a plug chop test, that is the true measure of your jetting.  If you ride it around the yard for a bit, and it stutters on top then clears out, your main is too rich.  If you feel poor response down low or at  1/8 to 1/4 throttle - your pilot circuit is rich.  Your plug should have a nice coco/tan color on it after the chop test.

Title: Is this too lean?
Post by: MyckMcClung on April 10, 2012, 04:25:38 PM

post pics

Title: Is this too lean?
Post by: arnego2 on May 16, 2012, 02:26:53 PM

Change one thing at the time, start with float height and go from pilot > needle > to main.

I run 45 pilot with a JD needle, on stock I'd run 48 height and average humidity comes close to mine too.
Stock needle 3 rd position, JD needle (red) 4rth position.