The Best Two Stroke Jetting Video You'll Ever See!

alright guys I'm gonna be covering the art of jet eot stroke today now this is gonna be a long super detailed video so you may want to sit down crack your cold one and enjoy this video alright let's get started so let's start at the simplest of levels what exactly is Jenny so jetting is changing out these little cylinder shaped pieces that have a whole throat just a tiny microscopic hole inside the carburetor here to allow for more or less fuel to enter the engine when you install a smaller jet that lets less fuel into the engine causing a leaner mixture and on the other side a bigger jet creates a richer mixture so that's like the bare basics of jetting and so what we're trying to achieve here is the optimal air to fuel ratio and for most engines that's gonna be 14 point 6 to 1 so that's one gram of fuel and fourteen point six grams of air to combine to make the perfect ratio now that number doesn't really matter and we're not going to use it for jetting and all more for just information purposes so what happens when an engine isn't jetted correctly if it's too rich mean too much fuel it'll bog out like you whack the throttle and it'll cop out and then it won't rub out all the way and then it'll cough and sputter throughout the upper rpm range too and if it's too lean it'll have a hanging idle meaning you rev it up and it takes forever to idle back down lacks power you may hear like a knocking noise to it it feels like super zingy it's kind of hard to describe that term and then it'll run super hot too if it's really lean and that's what leads to an engine seizure so obviously both of these are kind of dangerous conditions of being especially being lean that's what will destroy your top-end your crank and then if you're too rich you could cough out or bog out when you're riding especially kind of face of a jump or you know whoop section or whatever it might be and that obviously would not be a good thing to happen alright now that you kind of understand what jetting is all about let's talk about a few things before we actually start getting so say your bikes run like ass and you want to dive just right in the jetting and figure this thing out but there's a couple simple things you need to check / before you actually start pulling the carburetor apart and switching out Jets so first thing popping a new spark plug make sure your filter is clean those two things will make a big difference when it comes to jetting you have a plugged air filter that will just throw everything for a loop you know same thing with a a worn or really valid out spark plug make sure you have good compression may want to test the compression before you actually start jetting to diagnose any issues with that and then obviously make sure you have a clean carburetor there's no plug jets or plugged up vent hoses that'll really mess things up too if you just rebuilt your bike make sure you break it in that actually changes quite a bit once you have it broken in they'll create more compression and change how much fuel the engine requires oh and another big thing is float height if you don't have the correct flow height that'll actually change how much fuel is available in that float Bowl for the Jets that stuck out of so if that's off that'll make the whole jetting process kind of a nightmare and one more thing you want to make sure your bike is warmed up completely before you go out and test it just even swear I'm properly a cold bike runs way different than a warm bike does alright enough talking I'm gonna pull the carburetor off of this bike take it apart completely show you the ins and outs of the carburetor all the circuits what effects how it runs down low the mid-range and then when you've got it pegged up top so just kind of cover all the basics before we actually start with the jetting process oh and one more thing most bikes you can get to the carburetor or jet the carburetor if it's still on the bike you can do it with this one you just got twist the carburetor in there but for this time I'm just gonna pull it completely off show you guys the ins and outs like I was talking about earlier and then we can start swapping out jets and all that I'm gonna see how fast I can pull the carburetor off of this bike I'm hoping I can do it in under two minutes start the timer right now so there's four components here to the carburetor that we're going to check out that effective jetting and how the bike runs at a certain rpm the first thing we're gonna look at is the air screw on the backside of the carburetor don't mistake it for the idle screw which is usually on a throttle slide and towards the center of the carburetor and then number two we've got the needle on the throttle slide and then inside the float Bowl we've got the main jet in the pilot jet so the football is what contains the fuel and that's what the Jets draw feel from and ultimately what provides fuel to the engine all right I'm gonna pull the float Bowl off and show you guys the main jet the pilot jet and the floats as well so here we've got the main jet the pilot jet down here and the floats and then hanging on this little tab here on the floats is the float needle and that's what controls the fuel flow into the float Bowl earlier in the video I was talking about float height and how important it is to have the correct float height so the float height ultimately determines how much fuel is available in the float Bowl for the Jets to access and if you don't have enough fuel in there the bikes gonna be starving for a few obviously and if there's too much fuel in the float Bowl the bikes to me bogging out stumbling and just not running too well so to check your float height we're gonna let the floats extend all the way and then tilt the carburetor back and let them settle so right there they're settled but they're not pushing in the float valve so right there would be pushing in the float valve you want it sitting just right up on top and then you measure from the top of the float here to the float Bowl gasket surface and every bike is gonna be different so check your manual to see what the correct specification is and to adjust the float height you just bend this little tab that the float valve is hanging from so when you bend it down that increases the float height and bending it up goes the opposite way so definitely before you do any jetting make sure you have the correct float height in your carburetor there's a number of components here that affects how the bike runs throughout the RPM range so we're going to start at the very bottom so from idle to quarter throttle is the pilot jet this one right here and the air screw so the air screw is what controls how much air is being delivered to the pilot jet and this screw is how you tune in the pilot jet as well so with the air screw the farther you go in the less air is going to the pilot jet which creates a richer mixture and then turning that screw out brings more air in and creates a leaner mixture I'm going to talk about the air screw and the pilot jet later on in the video but basically how you tune in the pilot jet with the air screw is when you're at a certain amount of turns out with the screw that'll determine whether you should go up or down on the size of the pilot jet and then next up what controls from quarter throttle to 3/4 throttle is the needle here on the throttle slide so you can adjust it up or down and that changes how much fuel is being delivered throughout that throttle range and there's actually two more pieces here that factor in the jetting as well but they're not that applicable to most situations so I'm not really going to touch on it a whole lot so you can swap out your throttle slide for something different with a different cutaway or a different shape and that'll affect how much air is being let into the engine which obviously affects jetting and you can swap out your needle for something different to one last longer or shorter or a different taper here on the end but you're gonna notice the biggest difference in adjusting your existing needle up or down so the throttle slide just slides right into the carburetor right here and when you twist the throttle the slide goes up and down and allows the air and feel mixture into the engine so that needle goes down into the float Bowl and through the main jet so when you twist the throttle that needle allows fuel from the main jet to enter the engine and move the needle up or down you just reposition the clip on the needle in a different position there's usually like five or six different slots on the needle so when you move that clip down that raises the needle and creates a richer mixture and then when you raise that clip that lowers the needle and creates a leaner mixture and then last up we've got the main jet this jet makes the biggest difference of all your jetting changes and it's gonna be the most common jet you've got to swap out so this one controls from half throttle to wide-open throttle to recap we've got the air screw and this is what you use the tune in the pilot jet so the pilot jet and the air screw control from idle to quarter throttle and then we've got the needle which controls from quarter throttle to 3/4 throttle and last up is the main jet and this affects from half throttle to wide-open throttle so I'm gonna get this carburetor back together put it on the bike and then we can start the tuning process one last thing to discuss before we dive into jetting and that is what affects jetting and what kind of things require you to reject and that would be weather so like humidity temperature and then elevation is a big one too modification so if you did like intake or exhaust modifications of your bike that would require you to read jet and then maintenance things too like if you're lowering compression where you got a dirty air filter or other things just aren't up to par that will affect jetting too and how temperature affects your jetting is when the air is warmer it's less dense and so you'll need to go down on your jet to compensate so less air available means the requirement for less fuel and that when you go up in elevation the air is thinner so same concepts temperature less air available requires you to go down on your jet so for modifications generally that requires you to go bigger on your jet so if you have a more free-flowing intake or exhaust that is more air traveling through and that requires you would have more fuel as well one thing that's super important with jetting and will save you a lot of frustration is just going step by step and only make it one change at a time say if you change our needle position and your main jet to the same time and it negatively impacts how your bike runs you're not going to know which one affected that so just keep it simple so the first thing we're gonna tune in here is the air screw and the pilot jet now the pilot jet is gonna be the one adjustment you're gonna touch the least once you set it you're pretty much good to go with that and for the air screw when you change elevation or the temperature or humidity changes that is gonna be a screw you're going to adjust so how do you know if you have to lean or to rich of a pilot if it's to lean the idle will surge meaning you'll go up and down up and down and then when you crack throw all really quickly it'll cut out or bog and then it'll have trouble I linked down as well so you rev it up and it takes forever to idle back down and then when you have a rich pilot jet it'll sputter when you open the throttle it'll follow up plugs and it'll be really hard to start as well so how I'm gonna tune in the air screw and the pilot jet is by going three turns out on the air screw and then work my way back in half a turn at a time until the engine starts to stumble and the idle isn't very smooth then I'm gonna go back out half a turn at a time until that idle smooths out and the throttle response is crisp and wherever I end up with the air screw as far as turns out that will determine whether I need to go down or up on the pilot jet and there's a few other methods out there for tuning in the air screw such as adjusting the screw until the engine reaches its highest rpm but I've always found that going by the sound of the bike the throttle response and the idle that's always worked best for me now I'm going to fire up the bike let it warm up and then turn out this air screw the three turns out and then work my way in from there one one half to two and a half and three so the bike died when I turned that screw all the way in but now I'm at three turns out I'm just gonna start it back up and play with that screw some more so you could hear right there the thaw response is pretty crisp but I'm gonna start turning in the screw until it starts to bog out or starts to stumble when I turn the throttle and so as you're turning in that air screw and you get to a really rich position it'll sound like the choke is on so we'll have like a sputtering or like a really choked up sound to it and as you heard right there it bogs out pretty good and the idle just goes down really quick so definitely too rich of a position so I'm just gonna work my way out a half a turn out of time until it cleans up and then I'll count how many turns out I am on that screw so right there seem to be the sweet spot I turned the screw out until if our response cleaned up and the Idol smoothed out as well and now I'm going to show you guys what a lean condition will sound like I'm just gonna continue turning that screw out and we'll see what happens and so right there I'm about three and a half turns out and as you heard it takes a while for the Idol to go back down to normal and the throttle response is like super zingy just has like a light feeling to it the best way I could describe zingy is it just has like a different sound of the like the ding-ding-ding to it and once you play around jetting enough and messing with the air screw you'll be able to identify the difference between a normal tone of Idol and a lean tone of Idol and actually I forgot to check how many turns out I was earlier when I got it running crisp so I'm gonna take you through what it should sound like again I'm gonna start with the screw all the way in this time and back it out until I get it run really good again so right there is a sweet spot again good throw response and the Idol is pretty smooth see how many turns out I ended up at so that is gonna be a half one one and a half two and so two and a quarter so I'm gonna set it back to two and a quarter a quarter one right there so that's two and a quarter ideally you should have your airscrew between one and two and a half turns out if you reach the best running condition under turnout that indicates that your pilot jet is too lean so you have your screws so far in that you're barely letting any air in to make that good ratio and then on the other side of things if you have the screw more than two and a half turns out to get the best running condition that means your pilot jet is too rich so you're letting a ton of air in to make that good ratio once again so to recap if you're less than one turn in maybe bump your pilot up one size and then if you're more than two and a half turns out bump your pilot down a size so the only times you really need to mess with the air screw is if you have a really warm or really cold day where you go up or down in elevation or you add a modification to your bike so say if there's a really warm day you want to lean out the bike a little bit so maybe go a turn out or half a turn out I should say see how it runs and then if you go up in elevation you'll need to lean it out there too so once again try going half a turn out see how it responds and go from there and then if you add a modification such as a silencer or a pipe you want to rich ended up most of the time I mean usually the manufacturer the piper silencer will they'll tell you what you need to do there but you may want to go you know half a Turner or turn in and see how the bike runs with that so say you adjusted your air screw and you came to the conclusion that you're gonna need to swap out a pilot jet I'll show you how you can go about that without removing the carburetor from the bike so first you're gonna have to turn the fuel off and then loosen up the clamps on both sides the carburetor now with the clamps loose you can pivot it that way you can get access to the nut on the bottom of the flow bowl here and on this bike it's a little easier to remove the front sprocket cover just gives us a little more access to that football nut so this is a 17 millimeter and as soon as I loosen this nut up there is gonna be some fuel that's gonna come out so have something on hand to catch it or like a rag to soak it up so to give you guys a little better perspective on how to get access to that pilot jet we're gonna lay the bike on its side the jet you see right here is the main jet super easy to get access to but the pilot is up here in the front tucked way up in there and you have to fish around with a small flat blade screwdriver to get to it so you want to push up on the carburetor to get as straight of a shot with the screwdriver as possible you neither tilt the bike back up and the pilot jet will fall out or use a set of tweezers or needlenose pliers to get that pilot jet out of there and to get the pilot jet back in there just feed it in with a set of pliers or tweezers kind of push it up with a screwdriver right into the hole there you want to get a straight shot with that screwdriver that way you're not cross threading those threads either and it's pretty easy to get a false tighten here on the pilot jet if you have the screwdriver cocked at an angle when you're tightening it it'll feel like the pilot jets tight but it actually isn't and then you go to ride it and it falls out that's actually happened to me before and it feels like the world's crashing down like the bike just bogs out terribly and you wonder what the heck is going on you can just put the football cap back on tighten it up give it the carburetor back into place definitely want to make sure you tighten up your air boots clamps as well and then you can go test out that jet see how it responds all right so I've got the pilot jet and the Earth's crew all tuned in and next up for tuning is the kneel position here in the throttle so remember this is the part that controls from quarter to 3/4 throttle so to get to that needle I'll have to pull the cap here off the carburetor and so if you have a carburetor that has a screw on cap you know does a twist on cap it's pretty easy to get to it with the carburetor still on the bike but with this carburetor there's three screws holding the cap on and I've always found it easiest to just pull the whole subframe off like I had earlier on this bike it's also easier to remove the top shock bolt that way can pivot Chuck out of the way and get access to the carburetor it's only one extra bolt and it makes life a lot easier you just got to lift up on the back wheel kind of get some free play there and then just slide out the bolt and the shock will slide out of the frame slide the carburetor out of the intake manifold my way can get to these throttle cap screws here and then once all those screws are out the throttle slide this comes out of the carburetor you got to be really careful with that needle not to bend it too so this is the needle I'm talking about adjusting and with this carburetor just pull the spring the tension off the spring pinch the cable with your fingers like that push it down inside the throttle slide and it pops out and now we need to get access to the clips here on the needle so to get the needle out of the slide there's a bolt that holds the needle into place so right now I've got the clip in the middle position on the needle and the bike seems be running super good with it in that spot but I'm gonna show you guys what it would sound like or how it would run with this needle rich and all the way up so I'll remove the clip to the bottom position here so that's gonna raise the needle and rich in the condition and so I'm going to put the bike back together and see how it runs so that is the very bottom position here on the needle and if our days that clip to the top position that would drop the needle within the slide and lean out the condition so just like when I pulled it apart gonna have to compress the spring grab the cable kind of pinch it with my fingers I've got a good amount of cable poking out there and I'm just gonna slide it into the throttle slide and you'll be able to feel it hook and then you can release it sometimes this is a bit tricky to do when the cable is still on the bike so I've got the cable hooked inside the slide it's gonna release the spring make sure the cable is actually hooked to the slide and then this goes right back in the carburetor if you guys are enjoying the videos and are learning a lot I would really appreciate it if you support the channel by shopping over at Prime MX com I've got some hats t-shirts stickers and a few of the supplies I use throughout the videos over there as well and another way you could support the channel is by using the Amazon and eBay affiliate links at the bottom of the description so how this works is whenever you make a purchase through amazon or ebay through those links i get a small commission and it doesn't cost you anything extra so just a simple way of supporting the channel and what i do and so what you could do is set those links as a bookmark on your desktop or your mobile phone and whatever you want to make a purchase on amazon or ebay you just click through that link it'll be right there and it makes it really simple so i'd really appreciate it guys thank you finding the correct needle position can be pretty tricky and it's a lot easier to identify a rich condition rather than a lean condition so what I would do like I did here is start in a really rich condition and work your way leaner until it clears up so a rich conditions gonna sound like the choke is on it'll be sputtering and it won't accelerate as quickly as it should and so how you test the needle position is by warm up the bike and going through the gears only accelerate until about half throttle and if it starts to sputter out or cut out that means the condition is too rich and you're gonna have to bump that clip up a notch so try to just go one notch at a time or like with the Jets just go one size at a time so I'm gonna take this thing out and see how it runs with that clip in the richest position so like I was saying it's gonna bring the bike up to about half throw all throughout the gears and see if it sputters out or cops out at all any signs of a rich condition give that another shot here you can hear right in the mid-range there it's kind of cutting out which is right where that needle would be affecting it I'm just gonna make one more run down here and see if I can hear it a little more a little more clearly right there I'll go back in the first gear Yeah right there at super-rich and that's where the deal will be affecting in the right in the mid-range so I'm going to pull this thing back apart and move that clip position now I'm going to put that clip back into the middle position since it ran really good within that spot before so I'm gonna let the agent warm up and then I'm gonna take it down to drive it once again let me go until about a half throttle and I'll show you the difference between a needle position that's way too rich and one that's just right so like you heard before about half throttle it was super sputtering and it just did run very smooth and all that should be cleaned up now sounds a little better I think it needs to be cleared out just a little bit more definitely a lot of smoother running yeah that is a lot better keep in mind a keystroke has never gotta run perfectly food just together so she like what 25 like this isn't really meant to be run in the mid-range you know all day you're supposed to be more wide open with it so it's never gonna run just super smooth like a four-stroke does so you guys heard how the engine runs with that needle in the richest position but if it's on the leaner side of things the engine will sound kind of quiet and have like a dead feeling to it and when you give it full throttle they'll hesitate to so you always want to be on the richer side of things with the needle since it's kind of hard to identify it whether you're rich or lean with that without adjustment there so like I explained earlier you want to start with the needle and a richer position and then work your way leaner until it cleans up like I did here and now for the main jet I'm gonna do something pretty similar to what I did with the needle adjustment gonna start out really rich to the point where it's sputtering or it feels like the choke is on at high rpm and I'm gonna lean it out until all that clears up so once again you always want to be on the richer side of things just to be safe so right now the bike runs really good with the main jet where it's at but I'm gonna bump it up a few sizes and show you how it run in a really rich condition and then go through how it tuned in the main jet from there just like any other jetting change you want to make sure you've got the bike warmed up before you go and test it out so for the main jet it affects from half to full throttle so I'm just gonna go wide open and see how that fat our main jet affects it I'm guessing it's gonna sputter at full rpm because that jet was a size R - bigger than what I had there previously still need to be cleared out a little bit there's a little bit of clutter there though yeah you can definitely hear a little bit of spider at the very top there where it's like cuts out it's not completely smooth we're it's not clearing out 100% of the way so 1/8 overly rich it seems like but definitely on the richer side of things I'm gonna pop in the old debt I believe it was the 410 and I'll show you the difference that makes at the full full throttle there after running the bike for just a couple minutes with that bigger main jet we've got quite a bit of spooge coming out the silencer here definitely a bit rich so swapping out the main jet is going to be very similar to the pilot jet got the bike leaned over on a stand just going to loosen up the carburetor tilt it off to the side remove that nut on the bottom of the float Bowl here and then I'll be able to get access to the main jet alright one last little cashier should be running pretty crisp now sounds pretty good still a little bit of sputter up on top but it sounds better than it did before give it another couple runs down the driveway better sounds really really clean now yeah it's perfect just where I wanted to see it at yeah it sounds good yeah I'm gonna call that good right there if I really wanted to see exactly where I'm at for for jetting yeah rich I am I could do a chop test in the spark plug and that would tell me everything I need to know so if you want to see how a chop test is done on a spark plug just find the jetting or the spark plug video over on my channel to recap with a main jet you want to start out really rich and then work your way leaner until it cleans out on top and then just leave it up right there and it's always a great idea to do a spark plug chop test to see exactly where you're at with that main jet so that pretty much wraps up the ins and outs of jetting a two-stroke carburetor as you can tell if there's a lot of going by the sound and feel the bike and as you do it more and more you'll get a really good gauge whether you're too rich to lean or just perfect with your setting so it takes a lot of patience at first and you only want to make one change at a time so if you're messing with your pilot jet don't make a main jet change or a needle position change at the same time and don't make your changes too drastic either try to just keep it one size or like a quarter or half a turn that time and you'll really be able to dial it in another good resource for jetting specs is gonna be Google or like a pipe or carburetor manufacture safety put an F F pipe and silencer on your bike go check out their website or like pro-circuit or build wherever it might be they're gonna have some recommended jegging specs on the website for you to start with and then you can just kind of find - from there and if you did more extensive mods like say carburetor a big board or a stroker crank do a google search and forums like vital MX thumper talk or a few others will pop up and they'll have a good baseline spec for you to start with and then you can just kind of work from there - so the only difference between getting a two stroke and a four stroke is the air or the fuel screw on a two stroke it's called an air screw because it controls how much air is being let into the pilot jet circuit and then on the four-stroke it controls how much fuel is being let into the pilot jet circuit as well so on a two-stroke when you turn that screw in it lets air into the circuit creating a richer mixture and then on a four-stroke it's the opposite so you turn that screw in and it lets less fuel into the circuit creating a leaner mixture one thing I would recommend doing is check in the color your spark plug throughout the jetting process and afterwards as well so I have a couple fresh plugs on hand pop them in and keep an eye on them throughout so I actually did a video a really detailed video on how to check the color your plugs and there's also a lot more you can read from a spark plug as well and you can watch that video by clicking a circle right up here in the corner now if you think Jegs a bunch of BS and you want a way around it these electronic carbs are a really good way to go so basically how they work is they've got a metering rod inside of it which is able to automatically determine how much fuel the engine needs based on airflow volume and temperature so pretty much eliminates any need for jetting changes so this is the car blow up using on my cr250 build and I'll have a ton of videos coming out on the ins and outs of it how to set it up how it runs and my overall impression of it so lots of exciting content coming up soon now before I go I need to pick the winners of the works connection sticker packs from the last video so let's head over to the random color picker page and find out who the winners are so this is what I'm going to use to pick the winners here it is a random comment generator so I've got the URL punched in I'm gonna load up all the comments here should be quite a few in there probably over a thousand I'm guessing oh yeah 12:27 come down here hit the start button and that's gonna pick a just random comment from that video so the only requirement was you had a comment WC so first winner is motoboys he commented WC pick another one yeah didn't say WC you are wrong reference your service manual for the proper spark plugs readings sorry buddy gonna pick another winner all right Stephen Holsinger says WC so that's winner number two and then Aidan Zollner says would love to see a jetting video doing that right now WC so that's winner number three got two more so keep in mind if you see your name pop up here you got to send me a message here on youtube with your mailing address all right little dude isn't winner number four and the last one is JW films so all of you guys who won the stickers send me a message here on youtube you just got to go over to the about page on my channel hit the Sun mess send message button and shoot me your mailing address and I get those thicker packs mailed out all right that is gonna wrap up the video really hope you guys enjoyed it and learned a thing or two this video took a ton of time and effort to create it so I'd really appreciate it if you go hit that like button and subscribe to the channel as well thanks for watching and keep it Prime you

Channel: Cameron Niemela

Views: 440,885

Rating: 4.9175797 out of 5

Keywords: How To, Honda, Dirt Bike, Motorcycle, 2 Stroke, Two Stroke, Cameron Niemela, Niemela, Motocross, Honda CR125, CR125, 125 2 Stroke, Fixing Dirt Bike, Fixing Motorcycle, Fixing CR125, Fixing Two Stroke, Dirt Bike Problem, Broken Dirt Bike, Two Stroke Dirt Bike, CR125 Two Stroke, Two Stroke Engine, Jetting Two Stroke, Jetting Carburetor, ReJet Two Stroke, Two Stroke Tuning, Dirt Bike Jetting, Motorcycle Jetting, Dirtbike Bog, The Best Two Stroke Jetting Video You'll Ever See

Id: Uid8L4yMvfc

Length: 45min 57sec (2757 seconds)

Published: Tue Jul 03 2018