jetting help

[acrisby]

hey guys

looking for some jetting specs, i have A 2001 CR 125, fmf pipe and shorty. v force 3 reeds, bike is always abit sputtery on start of warm or cold, the bike came with these upgrades so have no idea what current jets are in it.just wondering what other people run for jets

 

[whenfoxforks-ruled]

I have an 83 CR480 that I acquired with out the stock keihn carb. The manual will do me no good for jetting a 38 mikuni carb though. But, any same bore MX bike that runs a 38 mikuni will give me a baseline. And the same oil ratio. The online parts micro fiches, usually point out the stock jet sizes for sea level to 1000 feet, and mild temperatures. If the engine does not respond to jetting changes correctly, something else is wrong. Adjust the air screw to obtain the highest idle, and count how many turns out it is. This will tell you where the pilot jet is at. The needle is a ride it and see adjustment. Make radical changes to see/feel and hear the differences. Use the choke to help differentiate between rich and lean. Check the plug for wet or dry works also. Too lean for jetting will not kill the engine, a 100 mile race may. The bike has to be in spec, or jetting is futile. Might as well yank the right crank seal and run premix oil in the tranny, and buy a quad to pull start it? From the air filter to the silencer, you have actually seen EVERYTHING is in order? Then read these, a few times anyways : http://www.dirtrider.net/forums3/showthread.php?t=92818 , http://www.dirtrider.net/forums3/showthread.php?t=108727 , http://www.dirtrider.net/forums3/showthread.php?t=48348 , http://www.dirtrider.net/forums3/showthread.php?t=172481&highlight=spankys+jetting+guide . Vintage Bobb