Why rejet when changing exhaust?
Because of the increased pressure required to push exhaust gas through them, more exhaust is left in the cylinders at the end of the exhaust stroke. Change the exhaust to something freer-flowing and you may create a stronger carb signal, requiring a smaller main jet.
Do you need to rejet carb with new exhaust?
If you’re just swapping the exhaust with a new one of the same type, there’s probably no need to rejet your carburetor at all. Where it becomes an issue is when you are installing a stronger or tuned exhaust. Doing so raises the running temperature of your engine and more fuel is needed to compensate.
Why do you have to rejet a carb?
A clean spark plug means you can skip the rejet. A black, sooty-looking spark plug means you’re running rich with too much fuel in your mix. If you see white residue, that means you’re running lean with too much air. In both cases, you need a rejet.
What does the FMF Mega Bomb do?
Used by Factory Teams, the MegaBomb is the next level technology you can have today. Produces long header torque and short header over-rev. The larger midsection creates a larger surface area for sound dissipation to reduce the sound output by as much as 1.5dB. Increases output from stock motor as much as 3 HP, alone.
Does an engine need exhaust back pressure?
As the pulses move along, they generate an exhaust flow. If you have a restrictive exhaust system, it can generate back pressure that works against the positive flow of the exhaust gas that’s trying to exit your vehicle. However, a little back pressure is a good thing. In fact, it helps.
What is better FMF or Pro Circuit?
The Pro Circuit has a little more throttle to rear wheel connection down on low end, but the FMF pulls stronger through the mid range. Up on top end both seem on par with each other and of course both have less over-rev than the stock muffler.
What is the difference between FMF PowerBomb and Megabomb?
The megabomb has a larger performance gain than the powerbomb, FMF claims a 3-5 HP increase, the down side is that it is only offered in Titanium so it is more expensive.
When do you need to change jet jetting?
Higher altitude (thinner air) requires less fuel or leaner jetting to run correctly. If adjustments don’t fix your rich/lean running problem, it’s time for replacements or you ride in varying geographies requiring constant tinkering with the jetting, consider purchasing a new jet kit.
What kind of fuel mix does jetting use?
We developed these specs with a 32:1 fuel to oil mixing ratio of a 50/50 mix of race fuel and super unleaded, 0 – 1500 ft altitude at 70 degrees outside temperature. Please note: There are way too many variables in jetting to give you a recommendation that works perfect.
What kind of fuel does FMF Racing use?
Here is what we’ve come up for in our area and is a great starting point for you as well. We developed these specs with a 32:1 fuel to oil mixing ratio of a 50/50 mix of race fuel and super unleaded, 0 – 1500 ft altitude at 70 degrees outside temperature.
What happens if you change the jet needle?
If it doesn’t, you’ll need to reestablish the main jet to its original position and then move on to the jet needle and so on. If you change all three you’ll never know what jet posed the air/fuel mixture problem, you’ll overcompensate to lean and create a bigger puzzle then necessary.
We developed these specs with a 32:1 fuel to oil mixing ratio of a 50/50 mix of race fuel and super unleaded, 0 – 1500 ft altitude at 70 degrees outside temperature. Please note: There are way too many variables in jetting to give you a recommendation that works perfect.
How do you know what jetting changes you need?
The only way to know what jetting changes you will need is by trial-and-error. No one can give you the perfect jetting specs because every bike is different. Every rider has a different style, and jetting is totally weather dependent.
Here is what we’ve come up for in our area and is a great starting point for you as well. We developed these specs with a 32:1 fuel to oil mixing ratio of a 50/50 mix of race fuel and super unleaded, 0 – 1500 ft altitude at 70 degrees outside temperature.
What should the jetting temperature be on a VP racing bike?
Please remember that sometimes the stock OEM jetting will work just fine, other times you may have to make an adjustment, so use our suggestions below as a guide to help with your jetting problem. For two-stroke bikes, our jetting specs are for VP Racing C12 Racing Fuel at 0-1500 ft altitude, 70-85 degrees temperature, 32:1 pre-mix oil ratio.