Inside A Motorcycle Carburetor - Main Jet Tuning | MC Garage

I'm on the

main

jet, have you ever heard that expression while bench racing with your friends, what the hell does that mean? Well, after this episode of MC Garage, you will know that today we talked about the

main

jet for the last few weeks. I've been going over a

carburetor

piece by piece, if you haven't seen the first few videos in the series go back and check them out. We will have links in the description below that cover the basic

carburetor

layout that we have covered. the float bowl and we have covered the pilot jet the next piece in the equation of a properly functioning carbureted

motorcycle

is the main jet the main jet is responsible for supplying the fuel which mixes with the air as it enters the engine after from the pilot the jet has finished doing its job at idle at about 20% throttle all the fuel goes to this bad boy right here is another part that meters fuel up to about 80% throttle but we'll cover that next week when fully open. you are at the main jet the main jet is located at the bottom of the carburetor inside the flow pole it is the larger of the two jets and is installed on the needle jet that is the part we will cover next week if this guy plugged in , you're in for a full carb cleaning ritual, usually everything will be clogged if this guy is plugged in.

Watch Ares' video on how to clean a carburetor. He links it below, so we'll assume you have a clean carburetor, so he can start to tell if the main jet from it is too rich or tune it first. Let's start with the manufacturer's recommendations in the service manual, as we discussed in last week's video. There will be a recommendation depending on temperature and altitude. This is where you want to start a lean condition means the air fuel ratio is too high there is simply not enough fuel this can cause problems from not making maximum power with the throttle and rpm wide open to knocking and noises that could damage the engine over time. of death by two hits with the possibility of a quick collapse and eventual seizure in 4 hits the damage might take a little longer but can still happen it's pretty easy to hear a ping on a two-stroke think of a towel tick that sounds like the noise of a ball bearing in a can, that's the sound of the fuel charge detonating before slamming into the piston before it reaches top dead center.

That same sound can be heard in a four-stroke engine, but the sound is masked by the sound of the valve train, listen to this, you will need to accelerate before you suffer serious damage. Also, a lean condition will have a crystal clear response, the top will feel weak and the bike will run much hotter than it should. Many times I've heard two-stroke racing saviors run so crisp and agile and then just stop, it's a classic case of seizures from being too skinny to fix that lean position, go up a jet size and run the bike again, repeat until now you find the correct size.

These numbers on the Jets' sides may not increase or decrease in increments of one. Usually it's a number like five or ten. When your

motorcycle

is rich, it means there is more than the optimal amount of fuel in the air charge. This leads to stumbles and overall poor performance, it doesn't lead to an early death like a link addition can, so if you have to err on the side of being rich, if the bike moves through the midrange and into the higher end, the power will increase. stumble and miss, is an easier condition to feel here for most people and it is very clear that it is malfunctioning, just drop the size of a jet and try it again on a two stroke engine.

You can also do a plug cut to check for proper jetty, that's quite a bit of process involved and we're going to save that for a separate video for now that's it for checking the main jet and that's all for this episode a messy

garage

the main jet is one of the simplest jets to set up, but it's not right, it's going to cause problems with next week's topic, needle jet and needle, if you like what we're doing, subscribe, share if you have any questions or comment, write it below, thanks for watching.