I saw a thread a few months ago that talked about jetting real clearly but i cant find it know. there was a formula for jetting where you start from WOT main adjustment and work your way backwards to pilot and air screw. going mostly by feel.it really made allot of sense. can anyone help me find this?
vandler
I posted this before:
"From experience (from my old racing days), I can give you a quick guide line:
Main Jet size goes down with higher elevation, we used .6%-.75% in size smaller for every 1000 feet in higher elevation.
Jet Needle clip position goes down with higher elevation; like from 4th position to 3rd clip position
Air screw opening (# of turns) goes out with higher elevation; like 1 3/4 turns to 2 ½ turns, or a ¼ turn for every 1000 feet"
As a reference point, you can take a factory stock 250R at 0-1000 feet elevation, 5-90 degrees (F), 150-156 Main, 3rd Needle Clip, and 2 turns out on the Air Screw. Then apply the changes per above as a basic guideline only.
Carlos.
"From experience (from my old racing days), I can give you a quick guide line:
Main Jet size goes down with higher elevation, we used .6%-.75% in size smaller for every 1000 feet in higher elevation.
Jet Needle clip position goes down with higher elevation; like from 4th position to 3rd clip position
Air screw opening (# of turns) goes out with higher elevation; like 1 3/4 turns to 2 ½ turns, or a ¼ turn for every 1000 feet"
As a reference point, you can take a factory stock 250R at 0-1000 feet elevation, 5-90 degrees (F), 150-156 Main, 3rd Needle Clip, and 2 turns out on the Air Screw. Then apply the changes per above as a basic guideline only.
Carlos.
If it was on here, I dont remember seeing it.
I realy think though, with all the different types of engine builds today, that there would not be a set type of jetting rules, other than going big as you can on the main jet & then work your way back down till it runs good.
Pilot jets, that normaly depends on your location across the states. Like upper midwest, those 250Rs can use like #60 pilot jets & then you get here in the east, Carolinas, we try to use a #50 & be flooding the engine to death, wont even idle at all.
It makes no difference who built an engine, how good they are as a builder, or if they can produce more power out of that engine than anybody else,,, that engine will last no longer than how smart that person is tunning on that carb.
Neil
I realy think though, with all the different types of engine builds today, that there would not be a set type of jetting rules, other than going big as you can on the main jet & then work your way back down till it runs good.
Pilot jets, that normaly depends on your location across the states. Like upper midwest, those 250Rs can use like #60 pilot jets & then you get here in the east, Carolinas, we try to use a #50 & be flooding the engine to death, wont even idle at all.
It makes no difference who built an engine, how good they are as a builder, or if they can produce more power out of that engine than anybody else,,, that engine will last no longer than how smart that person is tunning on that carb.
Neil
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