ya if u buy a new carb u will be in the same boat! for max performance out of any engine it must be properly tuned. if not it will either be a slug or u will pop it.
porting reed cage?
- Thread starter blasterman87
- Start date
Well some companies that sell carbs you can just tell them what you have done to your bike and they jet it accordingly, but alot of times that doesnt work either.
yeah i know it is just danged ol frustrasting tearing this thing apart then putting it back together, considering my garage doesn't have a heater! my jet kit arrives today, time to tinker!
dude, i can rejet my blaster in about 5 minutes. it takes absolutely no time at all. just make sure you've got the tools out and ready and it's quick as sh*t!
and unfortunately, there's no way to pre-calculate jetting. the only way to perfectly tune any carb on any machine is to slap a main and a pilot jet in there, put the needle on the middle clip and run the motor. check the plug in the idle circuit, fine tune, then check the plug in the main circuit, rejet as many times as necessary, then check the plug in the mid throttle circuit and adjust the needle accordingly.
and unfortunately, there's no way to pre-calculate jetting. the only way to perfectly tune any carb on any machine is to slap a main and a pilot jet in there, put the needle on the middle clip and run the motor. check the plug in the idle circuit, fine tune, then check the plug in the main circuit, rejet as many times as necessary, then check the plug in the mid throttle circuit and adjust the needle accordingly.
yeah not too fam with carbs, i am good with anything else on the bike but jetting this will be my first time, hey if you could tell me the easiest way to do it, i am all ears, on the bike or off easier?
thread officially jacked. lol
quam just told you. he's really pickin this stuff up. good job quam. i think you deserve +1 for the posts you've put up recently.
let us know what all you have done to it and we can SUGGEST a starting point.
quam just told you. he's really pickin this stuff up. good job quam. i think you deserve +1 for the posts you've put up recently.
let us know what all you have done to it and we can SUGGEST a starting point.
I copied this from another forum, it explains jetting vary simply.
If you take your time it's very easy. I would suggest writing down the changes you make as your doing it.
A correctly jetted carb makes a tremendous difference in the torque, midrange pull, top-end pull, and over-rev of your engine. If you have never jetted your bike correctly, you will almost certainly gain some performance at some point in the bike's powerband.
A cleanly jetted pilot circuit can be the difference between having to clutch the bike out of a turn or not. The needle can make all the difference in the world for the power of the machine in most situations, as it controls the throttle range that most riders spend most of their time using. the same time, his recommendations are meaningless.
Jetting is fairly simple, and is a useful skill to learn if you ride a two-stroke and want it to perform at it's best.
A correctly sized main jet could mean the difference between being able to rev out high enough to not have to shift one more time at the end of the straight, or the power falling flat on top and requiring you to make that extra shift.
Are you fouling plugs? Many people will tell you all sorts of band-aid fixes, from running less oil, to running a hotter plug. Both are incorrect fixes for plug fouling. It's all in the jetting.
The only way to know what jetting changes you will need is by trial-and-error. No one can give you jetting specs, because every bike is different, every rider has a different style, and jetting is totally weather dependent. Unless the person telling you what jets to use is riding an identical bike, on the exact same track, at It's very important that you start with the pilot circuit. The reason is simple. The pilot circuit affects the entire throttle range. When you are at full throttle, the main jet is the primary fuel metering device, but the pilot is still delivering fuel as well, adding to the total amount of fuel that your engine is receiving.
Before you start to rejet your bike, you need a clean air filter, a fresh plug (actually you need several plugs to do plug-chop tests for the main jet), and fresh fuel.
One important detail: Make sure the engine is in good mechanical condition. If your engine has a worn top-end, fix it first. Trying to jet a worn out engine is a waste of time. The same goes for reeds that don't seal properly, and a silencer that needs re-packing. Worn reeds will mimic rich jetting, and worn rings will mimic lean jetting.
Before you start the jet testing, Install a fresh plug. Set the float level to the proper specs, an incorrect float height will affect your jetting all across the throttle range.
Warm the bike completely, and shut it off.
As already stated, start with the pilot circuit. Turn the air screw all the way in, then turn it out 1.5 turns to start. Start the engine, and turn the idle screw in until you get a slightly fast idle, or hold the throttle just barely cracked, to keep the engine idleing. Turn the airscrew slowly in, and then out, until you find the point where the idle is fastest. Stop there. Do not open the screw any farther, or your throttle response will be flat and mushy, and the bike may even bog. This is only the starting point, we will still have to tune the air screw for the best response.
Now is the time to determine if you have the correct pilot installed in your carb. The air screw position determines this for you, making it very simple. If your air screw is less than 1 turn from closed, you need a larger pilot jet. If it is more than 2.5 turns from closed, you need a smaller pilot jet.
Once you have determined (and installed it if it's neccessary to change it) the correct pilot jet size, and tuned the air screw for the fastest idle, it's time to tune the air screw for the best throttle response. Again, make sure the bike is at full operating temperature. Set the idle back down (the bike should still idle, despite what you read in the Moto Tabloids), and ride the bike, using closed-to-1/4 throttle transitions. Turn the air screw slightly in either direction until you find the point that gives you the best response when cracking the throttle open. Most bikes are sensitive to changes as small as 1/8 of a turn.
The air screw is not a set-it-and-leave-it adjustment. You have to constantly re-adjust the air screw to compensate for changing outdoor temps and humidity. An air screw setting that is perfect in the cool morning air will likely be too rich in the heat of the mid-day.
Now, it's time to work on the needle. Mark the throttle grip at 1/4 and 3/4 openings. Ride the bike between these two marks. If the bike bogs for a second before responding to throttle, lower the clip (raising the needle) a notch at a time until the engine picks up smoothly. If the bike sputters or sounds rough when giving it throttle, raise the clip (lowering the needle) until it runs cleanly. There isn't really any way to test the needle other than by feel, but it's usually quite obvious when it's right or wrong.
Last is the main jet. The main jet affects from 1/2 to full throttle. The easiest way to test it is to do a throttle-chop test. With the bike fully warmed up, find a long straight, and install a fresh plug. Start the engine, and do a full-throttle run down the straight, through all gears. As soon as the bike tops out, pull the clutch in, and kill the engine, coasting to a stop. Remove the plug, and look deep down inside the threads, at the base of the insulator. If it is white or gray, the main is too lean. If it is dark brown or black, the main is too rich. The correct color is a medium-dark mocha brown or tan.
Once you have a little bit of experience with jetting changes, and you start to learn the difference in feel between "rich" and "lean", you'll begine to learn, just from the sound of the exhaust and the feel of the power, not only if the bike is running rich or lean, but even which one of the carb circuits is the culprit.
The slide is also a tuning variable for jetting, but slides are very expensive, and few bikes need different slides, so we won't go into that here.
Keep in mind, even though this article is intended primarily for two-strokes, four-strokes also need proper jetting to perform right, although they are not quite as fussy as their oil-burning cousins. The only real difference in the two is with the pilot circuit.
Two-strokes have an air screw that you screw in to make the jetting richer, ansd screw out to make the jetting leaner. Four-strokes, on the other hand, have a fuel adjustment screw that you screw in to make the jetting leaner, and out to make it richer.
If you take your time it's very easy. I would suggest writing down the changes you make as your doing it.
A correctly jetted carb makes a tremendous difference in the torque, midrange pull, top-end pull, and over-rev of your engine. If you have never jetted your bike correctly, you will almost certainly gain some performance at some point in the bike's powerband.
A cleanly jetted pilot circuit can be the difference between having to clutch the bike out of a turn or not. The needle can make all the difference in the world for the power of the machine in most situations, as it controls the throttle range that most riders spend most of their time using. the same time, his recommendations are meaningless.
Jetting is fairly simple, and is a useful skill to learn if you ride a two-stroke and want it to perform at it's best.
A correctly sized main jet could mean the difference between being able to rev out high enough to not have to shift one more time at the end of the straight, or the power falling flat on top and requiring you to make that extra shift.
Are you fouling plugs? Many people will tell you all sorts of band-aid fixes, from running less oil, to running a hotter plug. Both are incorrect fixes for plug fouling. It's all in the jetting.
The only way to know what jetting changes you will need is by trial-and-error. No one can give you jetting specs, because every bike is different, every rider has a different style, and jetting is totally weather dependent. Unless the person telling you what jets to use is riding an identical bike, on the exact same track, at It's very important that you start with the pilot circuit. The reason is simple. The pilot circuit affects the entire throttle range. When you are at full throttle, the main jet is the primary fuel metering device, but the pilot is still delivering fuel as well, adding to the total amount of fuel that your engine is receiving.
Before you start to rejet your bike, you need a clean air filter, a fresh plug (actually you need several plugs to do plug-chop tests for the main jet), and fresh fuel.
One important detail: Make sure the engine is in good mechanical condition. If your engine has a worn top-end, fix it first. Trying to jet a worn out engine is a waste of time. The same goes for reeds that don't seal properly, and a silencer that needs re-packing. Worn reeds will mimic rich jetting, and worn rings will mimic lean jetting.
Before you start the jet testing, Install a fresh plug. Set the float level to the proper specs, an incorrect float height will affect your jetting all across the throttle range.
Warm the bike completely, and shut it off.
As already stated, start with the pilot circuit. Turn the air screw all the way in, then turn it out 1.5 turns to start. Start the engine, and turn the idle screw in until you get a slightly fast idle, or hold the throttle just barely cracked, to keep the engine idleing. Turn the airscrew slowly in, and then out, until you find the point where the idle is fastest. Stop there. Do not open the screw any farther, or your throttle response will be flat and mushy, and the bike may even bog. This is only the starting point, we will still have to tune the air screw for the best response.
Now is the time to determine if you have the correct pilot installed in your carb. The air screw position determines this for you, making it very simple. If your air screw is less than 1 turn from closed, you need a larger pilot jet. If it is more than 2.5 turns from closed, you need a smaller pilot jet.
Once you have determined (and installed it if it's neccessary to change it) the correct pilot jet size, and tuned the air screw for the fastest idle, it's time to tune the air screw for the best throttle response. Again, make sure the bike is at full operating temperature. Set the idle back down (the bike should still idle, despite what you read in the Moto Tabloids), and ride the bike, using closed-to-1/4 throttle transitions. Turn the air screw slightly in either direction until you find the point that gives you the best response when cracking the throttle open. Most bikes are sensitive to changes as small as 1/8 of a turn.
The air screw is not a set-it-and-leave-it adjustment. You have to constantly re-adjust the air screw to compensate for changing outdoor temps and humidity. An air screw setting that is perfect in the cool morning air will likely be too rich in the heat of the mid-day.
Now, it's time to work on the needle. Mark the throttle grip at 1/4 and 3/4 openings. Ride the bike between these two marks. If the bike bogs for a second before responding to throttle, lower the clip (raising the needle) a notch at a time until the engine picks up smoothly. If the bike sputters or sounds rough when giving it throttle, raise the clip (lowering the needle) until it runs cleanly. There isn't really any way to test the needle other than by feel, but it's usually quite obvious when it's right or wrong.
Last is the main jet. The main jet affects from 1/2 to full throttle. The easiest way to test it is to do a throttle-chop test. With the bike fully warmed up, find a long straight, and install a fresh plug. Start the engine, and do a full-throttle run down the straight, through all gears. As soon as the bike tops out, pull the clutch in, and kill the engine, coasting to a stop. Remove the plug, and look deep down inside the threads, at the base of the insulator. If it is white or gray, the main is too lean. If it is dark brown or black, the main is too rich. The correct color is a medium-dark mocha brown or tan.
Once you have a little bit of experience with jetting changes, and you start to learn the difference in feel between "rich" and "lean", you'll begine to learn, just from the sound of the exhaust and the feel of the power, not only if the bike is running rich or lean, but even which one of the carb circuits is the culprit.
The slide is also a tuning variable for jetting, but slides are very expensive, and few bikes need different slides, so we won't go into that here.
Keep in mind, even though this article is intended primarily for two-strokes, four-strokes also need proper jetting to perform right, although they are not quite as fussy as their oil-burning cousins. The only real difference in the two is with the pilot circuit.
Two-strokes have an air screw that you screw in to make the jetting richer, ansd screw out to make the jetting leaner. Four-strokes, on the other hand, have a fuel adjustment screw that you screw in to make the jetting leaner, and out to make it richer.
wow due thanks thats reallly helpful, i appreciate you not being a dick about it either, like i said i am good with everything else but never messed with jetting, so thanks a lot, do you know where there are pics of jetting, can i do it with the carb still on the bike? which needle is the main, pilot jet?I:II:I
you can do it on the bike, just loosen the clamps to turn the carb a little on it's side. make sure u turn the fuel off at the petcock first. when you remove the bowl, the main jet is the brass hex with a hole in the middle that sticks down the lowest. i think it has a white plastic piece around it. if i am thinking right the pilot jet is more towards the engine side of the carb, it's longer and skinnier, on most bikes it's removed with a flat head screwdriver, not completely sure if it's this way on a blaster.
Look up a diagram of your carb and print it, take it with you and refer to it if you need to. I'd take the carb off the first time around and clean it real well, after that you can just loosen it up and turn it to access the bowl and jets. You should be able to get the top off as well without removing it.
i will probably be doing this tomorrow, or friday, would you be around for help if i have problems, pm me ur msn name possibly, like i said not too big on this but want to learn to do it, thanks.
thanks hick. i've been working on 4stroke motorcycles for awhile now and have rejetted countless carbs, but this blaster is def the 1st and only 2stroke i've ever worked on and this 4m has taught me a sh*t-ton about it!
love this site and have learned a lot from it.
2smoker85, the jets (main and pilot) are inside the float bowl. you'll need to remove the 4 phillips bolts to get to them. as stated before, it's a great time to just rebuild the carb if it hasn't been done in some time. new gaskets, a good cleaning, etc....the needle position is adjusted by removing the cylindrical slide and pulling the needle out and adjusting the small clip on the needle up or down the slots. then there's the air screw which will meter the amount of air being fed into the pilot circuit. turn out for more air, in for less air.
love this site and have learned a lot from it.
2smoker85, the jets (main and pilot) are inside the float bowl. you'll need to remove the 4 phillips bolts to get to them. as stated before, it's a great time to just rebuild the carb if it hasn't been done in some time. new gaskets, a good cleaning, etc....the needle position is adjusted by removing the cylindrical slide and pulling the needle out and adjusting the small clip on the needle up or down the slots. then there's the air screw which will meter the amount of air being fed into the pilot circuit. turn out for more air, in for less air.
