does changing the main jet size effect proformance noticeablelly' if you go bigger? or is it more to prevent blowing up?
stupid jetting question
- Thread starter almightythor
- Start date
u only need to rejet when u put mods on, if u put a power up jet kit on it might give it more power, idk, but mostly so u don't fry the engine
yea i just put on boysen power reeds and a 5/16 spacer i'm gonna do a chop 2morrow an see color i didnt rejet yet it seems to run strong all the way through 6 so i dont know
yea its mandatory i check mine i'm really behind on it i've got $2500 in upgrades and never checked my jets could be stock for all i know just seems to run good so i dont want to mess with it plus im not confadent in opening up the carb
dude changing main jets are easy, pop the bottom(bowl) of the carb off carefully and the main is right in the middle, take a small socket or socketheaded screwdriver and take it out. put the new one in so that its tight but not hercules or you'll strip it out.
Jets control air/fuel ratio. the pilot and airscrew from 0 to 1/4 throttle, the needle and slide 1/4 to 3/4 throttle and main from 3/4 to WFO. This is how far the throttlle is open, not how fast you are going or what RPM the motor is running at. As air passes over the jet it draws (sucks) fuel. The bigger the jet, the more fuel it will pass. The faster the air moves (velocity) the more fuel it will pull. The motor needs a the ratio between air and fuel to be in a certain range to run. Inside that certain range, if the ratio is too rich, (more fuel to air) the bike will not run good, and will run cooler and can cause plug fowling. If the ratio is to lean, (less air to fuel) it will not run good and will run hot. the temperature can then become so hot that it will melt the metal in the piston and rings causing a siezure. As little as 500 feet of elevation, or 10 degree difference in temperature, or changes in barometric pressure can effect jetting.
there is a semi broad range of jetting that a bike will run in, but it will not run good. There is a very pricise edge that will make the bike perform to its potential. Proper jetting can make as much as a 25% difference in power.
an EGT measure the exhaust temp, which will reflect the temperature that the fuel/air mixture is burning at. by knowing that temperature you can jet you bike as precelsy as possible, making as much power as possible as well as knowing when you need to change jetting because the conditions have changed.
FWI: most bikes are not jetted correctly. Most siezures are not mainjet related. they are usually caused by the needle or slide being wrong. Your hauling ass wide open, the bike is running hot but withen an acceptable range, the second you back of the bike becomes instantly lean, temp spikes sky high and piston melts/sticks.
When was the last time you did a half or 3/4 throttle under load plug chop??
*Disclaimer* this has been somewhat over simplified for the sake of making it easily understandable.
Anything you do can effect jetting, bore job, reeds, air cleaner etc.
there is a semi broad range of jetting that a bike will run in, but it will not run good. There is a very pricise edge that will make the bike perform to its potential. Proper jetting can make as much as a 25% difference in power.
an EGT measure the exhaust temp, which will reflect the temperature that the fuel/air mixture is burning at. by knowing that temperature you can jet you bike as precelsy as possible, making as much power as possible as well as knowing when you need to change jetting because the conditions have changed.
FWI: most bikes are not jetted correctly. Most siezures are not mainjet related. they are usually caused by the needle or slide being wrong. Your hauling ass wide open, the bike is running hot but withen an acceptable range, the second you back of the bike becomes instantly lean, temp spikes sky high and piston melts/sticks.
When was the last time you did a half or 3/4 throttle under load plug chop??
*Disclaimer* this has been somewhat over simplified for the sake of making it easily understandable.
Anything you do can effect jetting, bore job, reeds, air cleaner etc.
