JTurn36178
~SPONSOR~
- May 17, 2002
- 131
- 0
I, or should I say we, have two YZ 250's.
(Both have stock expansion chambers, & carbs)
Mine a '96 with a 3" flywheel (with goofy power valve chamber.) Mine has good mid to top pull. But has always had a hesitation off the bottom. I have advanced the timing slowly over a loooong periond of time. As best as I can measure about 3/16" ahead of the factory mark. No ill effects as yet. (By the way It's a real dog at the stock setting.) Every move I have made has improved the performance.
My son's a '94 with a 4" flywheel. His runs great with a little change in jetting once in a while. His timing is barely moved in the advanced direction past the factory mark.
During the rain this week I have done a little research. I have installed a dial indicator in both motors to check the difference from top dead center to the mark on the flywheels.
My son's flywheel mark is .056" before TDC.
My engine flywheel mark is .008" before TDC.(after I have advanced it.) It runs so well at that I sure wasn't going to go back to stock.
I realize they are two different cylinders with possibly different port heights etc. that would cause the differences.
Assuming that the mark on the flywheel is some sore of reference point related to the cdi trigger, on both bikes.
I would like to know if any of you have expierences with these and could explain why his engine tolerates the large difference in advance. (or so it seems a difference.)
I discussed this topic in the general repairs forum once and was blown off as some type of idiot. I'm real close but still like to have fun.
Thanks for any ideas.
Jim
(Both have stock expansion chambers, & carbs)
Mine a '96 with a 3" flywheel (with goofy power valve chamber.) Mine has good mid to top pull. But has always had a hesitation off the bottom. I have advanced the timing slowly over a loooong periond of time. As best as I can measure about 3/16" ahead of the factory mark. No ill effects as yet. (By the way It's a real dog at the stock setting.) Every move I have made has improved the performance.
My son's a '94 with a 4" flywheel. His runs great with a little change in jetting once in a while. His timing is barely moved in the advanced direction past the factory mark.
During the rain this week I have done a little research. I have installed a dial indicator in both motors to check the difference from top dead center to the mark on the flywheels.
My son's flywheel mark is .056" before TDC.
My engine flywheel mark is .008" before TDC.(after I have advanced it.) It runs so well at that I sure wasn't going to go back to stock.
I realize they are two different cylinders with possibly different port heights etc. that would cause the differences.
Assuming that the mark on the flywheel is some sore of reference point related to the cdi trigger, on both bikes.
I would like to know if any of you have expierences with these and could explain why his engine tolerates the large difference in advance. (or so it seems a difference.)
I discussed this topic in the general repairs forum once and was blown off as some type of idiot. I'm real close but still like to have fun.
Thanks for any ideas.
Jim