Up Grades for my motorcycle

[YZER-409]

I have a yz125 and I want to put new Moto Tassinari VForce3 reeds on my bike, if i do this do i have to change the jetting or mess with anything else. Also I would like to put either a FMF fatty or a pro circuit works or platnium pipe on my bike and if i do put a new pipe on do i have to change the jetting. Thanks for your help.

[Faded]

Originally Posted by YZER-409

...if i do this do i have to change the jetting...

Four out of five dentists recommend it.

[Satch0922]

I have a different bike however the VForce did not mess my jetting up (this warm humid weather did though!)

More than likely if you go with a reed and a pipe your gonna have to rejet. But that is not a bad thing. There are threads here in the Knowledge Base Forums that can help you with that.

[MotoMojo17]

Yes, you will most likely have to change your jetting with the V Force 3s.

[YZER-409]

Will i have to get a smaller or a larger jet, and will i have to change things like my piolet jet, needle, and the needle position.

[RaptorRacer888]

Originally Posted by YZER-409

Will i have to get a smaller or a larger jet, and will i have to change things like my piolet jet, needle, and the needle position.

Most likely a larger jet, and I would only change one thing at a time instead if this is your first time, so that if something goes wrong you know what it is and your not hunting down a problem.

But if your comfortable with it, you will probally will have to go up on the main and pilot at least, and adjust the air fuel screw.

[scooter842]

Heres a guide that i go by anytime i need to rejet.. It has worked wonders for me and some of my other fellow 2 stokers.. I would install your v force, pipe and whatever else you want on your bike and start over using this guide:
Spanky's Jetting Guide:

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.

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 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.

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.

So there you have it Print it out a few times and leave one in your toolbox, in your truck or whatever so that you always have it when you need it. Good luck

[YZER-409]

I have two more quick questions, First what type of pipe should i get, pro circuit or fmf, Second do the parts give me a noticable power difference.

[Roostman]

Go with either pipe, they are both good pipes. No theyre not gonna transform your bike into a firebreathing drag bike but they will reshape the power in favor of a more linear albiet stronger in some areas and a better top end than the stock pipe usually provides. Youll like the change more than likely but there really isnt a huge difference over a stock pipe. Youd be better off getting the suspension tuned for you for a little more loot (about $400), that WILL give you the confidence you need to ride harder through the rough stuff.

[Faded]

IMHO any pipe but the FMF SST if you have to have one. For a more noticable power difference (read: larger gains) porting would be my choice over both reeds and a pipe, baring any reliability issues, and can be had for not much money ($150-ish). Most people aren't too keen on porting due to it not being "irreversible" and would rather just go the bolt-on route.

[YZER-409]

What do they do when they port your bike, and if i do get reeds do i have to mess with the needle positoin on my carb.

[bikepilot]

You will always have to mess with your carb settings. Any changes releated to the engine can change the fuel requirements. Even if you don't change the engine, changing tempatures, humidity and altitude will necessitate regular jetting changes. Frequent re-jetting is a fact of life with a high-performance carb'd bike, get used to it and good at it and enjoy an exlclent running machine!!

[kwmotocrosspunk]

i put a v-force 3 reed valve, a pro circuit platinum pipe and pro circuit r304 shorty race cap silencer, (among other things), on my yz80 and ya i had to rejet but it flies so much faster than it did before