How To Tell If Pilot Jet Is Rich or Lean [Jetting Symptoms]

Рет қаралды 50,182

5 ай бұрын

Learn how to easily tune the air/fuel screw in just a few minutes:
2 stroke - motocrosshideout.com/carb/
4 stroke - motocrosshideout.com/fuel/
Wondering if your pilot jet is rich or lean but not sure and don't want to make the mistake of adjusting the wrong jet circuit and causing more problems?
This simple and practical video will show you how to tell if it's your pilot jet (air/fuel screw) circuit that's causing the problem and how to tell if it's rich or lean based on signs and symptoms that you can hear, see, or feel when starting or riding your dirt bike, whether it's a 2 stroke or 4 stroke with a carburetor.
Motocross Hideout is my personal brand to help new riders learn to properly and safely ride a dirt bike so that you don't crash and miss out on life because of an injury. My Virtual Dirt Biker School is an online riding course/camp that teaches anyone new to dirt bikes the basic techniques to stay in control and become a better rider faster. I've taught many first-time riders over the years, both guys and girls, young and old.
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Disclaimer: Dirt biking can be dangerous if you don't respect the bike or terrain. This video shows you tips to help keep you safer as well as improve your riding technique and skill so that you stay in control while riding. I, Kelley Fager from Motocross Hideout, am not held responsible for a crash resulting in an injury from trying these techniques. Please use proper dirt bike riding gear to help prevent an injury.

Пікірлер: 111

@MotocrossHideout 5 ай бұрын

Learn how to easily tune the air/fuel screw for the pilot jet circuit in just a few minutes: 2 stroke - motocrosshideout.com/carb/ 4 stroke - motocrosshideout.com/fuel/

@williamlambie57 3 ай бұрын

A xpro titan 250 I bet it just can't handle it

@zachzat1581 3 ай бұрын

@@williamlambie57I bet it can

@vijayam1 Ай бұрын

Brilliant one as always!

@TalhaKhan-pi5tk Ай бұрын

best video yet fr fr

@str8mac842 5 ай бұрын

Real good video thank you I learned something today for sure

@MotocrossHideout 5 ай бұрын

Awesome - thanks for watching!

@gowengetter4599 5 ай бұрын

Completely agree with you mate. Good explainer video

@MotocrossHideout 5 ай бұрын

Much appreciated, Gowen. Thanks for watching.

@samcolletti4230 Ай бұрын

Good to know on the blub blub symptom. Trying a rejet. Thanks

@MotocrossHideout Ай бұрын

Let us know how it goes :)

@jvnnis 3 ай бұрын

sick video!

@chrisrose2898 5 ай бұрын

Good stuff my friend! Thanks

@MotocrossHideout 5 ай бұрын

Thanks, Chris!

@billyschannel997 5 ай бұрын

Great video and explanation

@MotocrossHideout 5 ай бұрын

Glad you liked it, Billy.

@nastysoda9212 5 ай бұрын

Thank you! I jsut switched to 100LL fuel and it's running rich, will bring the pilot jet down a size and see tomorrow

@MotocrossHideout 5 ай бұрын

Yep, going to a higher octane gas will naturally make it run richer because it burns slower. Let us know your results! I'd recommend grabbing my free air/fuel screw tuning guide as well ;)

@zachzat1581 3 ай бұрын

My bike runs perfect up to half throttle bogs out// misfires// backfires a little bit after half throttle to full throttle if you could do a video on main jet bog it would be great

@shaakirmir6722 2 ай бұрын

Hey bro need advice, I got a 125 2 stroke with oil injection. My bike smokes quite a lot on startup and leaves a black trail of oil out the silencer with every ride. The oil pump settings are factory and I’m coming to the possibility of the pilot jet being too rich?

@ALLCITY402 2 ай бұрын

My yz80 only idles with choke on soon as I try to turn choke off bogs down and dies lots of smoke

@antonionegrete33 2 ай бұрын

I was driving my 93cr 250r today and I was going to stop and I pulled the clutch and came to a stop and it just died clutch is good won’t start good compression good gas flow idk what’s wrong

@OG-sp4vs 2 ай бұрын

Just letting you know your videos are great very helpful now tell me if I'm getting this correctly im working on a DKW two-stroke 125 starts up perfect no problem there when I hit the throttle it bogs out so what you're saying it could be my pilot jet too rich? Thanks again for the videos

@MotocrossHideout 2 ай бұрын

Glad you find them helpful :) Check out this video for more info on bogging: kzfaq.info/get/bejne/i5-qrdeblp6amGg.html

@D_gas_bob 17 сағат бұрын

What if it starts and runs fine, but has rapid backfire when decelarating?

@Altanabstick 15 күн бұрын

Can you explain the difference between rich sputter and lean surging?

@MotocrossHideout 12 күн бұрын

kzfaq.info/get/bejne/i5-qrdeblp6amGg.html

@markcoyne5811 Ай бұрын

Iv got a 70 kit with upgraded carb can get it to idea and sit there, but when riding soon I come on to power band it sputtering like made

@MotocrossHideout Ай бұрын

Sounds like the main jet might be too rich/big.

@problemx3526 Ай бұрын

My bike dies when idling hot, I screwed it richer and it worked but now in my way to the gym it almost drowned itself when starting from a intersection so too rich (2stroke bike)

@endastlur4788 5 ай бұрын

Hey man. Nice video you got here. I just recently got my first dirtbike. The engine is a Lifan 125cc 8,9hk four stroke, and the bike is one of these small chinese types mid size. It has been sitting from time to time since it was bought new at 2011. It has very low hours layed down on it, maybe a couple at most. It runs realy nice at all rpm but it hasitates when I go full power and go through all the gears on the straights. So every time I shift up and hit the throttle it kinda sputters or hasitates for a brief moment. It lasts not even a second, but it's easier to notice at higher gears. I suspect that it is a carb thing, but before I put the carb of I'm curious to what you think about it.

@MotocrossHideout 5 ай бұрын

Congrats on your first dirt bike! Here's my video on a rich bog vs lean bog: kzfaq.info/get/bejne/i5-qrdeblp6amGg.html Yours sounds like it's running rich. I would try cleaning the air filter first. If it still hesitates, the main jet might be a little too rich if it sputters when you give it full throttle.

@endastlur4788 5 ай бұрын

@@MotocrossHideout Thanx man. Your soundeffects are spot on 😁 I actually did screw the air/fuel screw both in and out, and other issues showed up that clearly was rich/lean rellated. But the sputter remained. Next thing will be checking the airfilter and probably also pull the carb of to see how it looks after sitting all these years. Thanx once again man!

@evankufahl2309 2 ай бұрын

Hey I just picked up a kx112 and it starts 1st or second kick when cold and hot but sputters pretty good right before the powerband and then smooths out. What do you think could be the issue? Also it doesn’t like to idle (even when hot)and sort of seems like it hangs but I’m new to two strokes and can’t really tell. Any idea what’s going on? Thanks!

@stepanrais5534 Ай бұрын

rich main jet ?

@kenmartin2454 3 ай бұрын

Please help. Im confused. I bought a Yamaha yz250f 2007. Came out the shop 20 hours ago. It starts very easy cold, 1-3 kicks and idles good. When i pull the choke out it revs high. Also when i throttle it when cold it has hanging idle. When i ride it it gets the rich bog where it hesitates whenever i give it gas, it happens eaven in 4rth gear high rpms but not so often as in the middle revs. Also when it gets warm it WILL NOT start unless i give it throttle while i kick it, then its a first kick start. Also it doesnt idle when hot. But weirdly today after heavy riding it randomly idled when hot. Which is rare.

@MotocrossHideout 3 ай бұрын

Sorry to hear about your issue. A hanging idle is usually caused by a lean fuel screw/pilot jet or an air leak (loose clamp/cracked intake, or missing fuel screw o-ring). I recommend grabbing my free fuel screw guide and starting there. Let us know how it goes!

@bronco_4.3 Ай бұрын

My sp400 will idle great but if you give it barley any throttle it revs up then if you go anymore it cuts out will pop sometimes any ideas?

@Spacecruizer203 5 күн бұрын

Too rich or jet is clogged most likely gotta get that carb off start from the beginning check the gaskets ect spark plug and cdi wires

@jeffwendorf170 2 ай бұрын

Just put a fresh top end on a 15 husky te 125 , now it will only start with the throttle wide open, I cleaned the carb twice throughly

@MotocrossHideout 2 ай бұрын

Hey Jeff, sounds rich. Have you tried adjusting the air screw? Make sure your carb float level is set correctly and that the reeds aren't cracked/worn.

@jeffwendorf170 2 ай бұрын

excellent thank you for the feedback sir, I will check all the above

@Ifeelgreyt1738 5 ай бұрын

Hey man, I have a 1998 yz125 and I wanna trail ride it but I don’t know what fuel ratio to run it in and it’s really rich right now wondering if you can help me or give me tips.

@jaydenriley6739 5 ай бұрын

Yz's usually run 32:1 and if it's rich them wind out the air screw a bit till she runs right

@MotocrossHideout 5 ай бұрын

Yep, Jayden gave some great advice! If you need help with tuning the air screw, grab my free guide here: motocrosshideout.com/carb/

@WestHaddnin 20 күн бұрын

What if it sounds like rev limiter after 1/4 of a throttle?

@MotocrossHideout 19 күн бұрын

Rich sputter.

@mysticalmisfit33 2 ай бұрын

Got a 1990 dr250s, just cleaned the carb, replaced air filter, cleaned out the gas tank… I can only bumpstart it and when it’s running, It’s giving me the to lean symptoms… Any pointers?

@peytonedwards4225 11 күн бұрын

He doesn't mention your float bowl has to be the right height. Your pilot number size up or down. Intermittent spark.

@Jermain3_ 5 ай бұрын

My cdi box broke yesterday is it because iam riding with no battery in my bike?

@MotocrossHideout 5 ай бұрын

What bike? Did you remove the battery?

@emis.2217 3 ай бұрын

how about pingin ,What would it be then? I have a KTM 300 EXC 2013 and when it gets very hot the idle comes back harder and pings

@MotocrossHideout 3 ай бұрын

It's usually caused by using gas with too low of an octane rating (or perhaps if the gas has sat too long). A KTM 300 should be using 91-93 octane if it's stock. If it happens to have higher compression than stock, then you'll need to mix or use higher octane gas to prevent detonation (pinging), if that makes sense.

@emis.2217 3 ай бұрын

@@MotocrossHideout something like this I didn't think about for half a season I changed the cylinder head with one of S3 Enduro something like lower compression but in reality it is higher than what stock , And before it was going perfectly I'll try a higher octane mix thx

@MotocrossHideout 3 ай бұрын

Sounds good, let us know your result!

@jacobgore8978 2 ай бұрын

I got a crf250 my bike hard to start sometimes it back fires and pops and it dont idle what do you think it is

@MotocrossHideout 2 ай бұрын

Sounds like it might be running lean. Either needs a fuel screw adjustment or the pilot jet circuit cleaned is my best guess.

@jacobgore8978 2 ай бұрын

@@MotocrossHideout ok thank you for the reply turns out bikes was sat for a couple of months

@MotocrossHideout 2 ай бұрын

@@jacobgore8978 Gotcha, yeah pump gas can go bad in a matter of weeks. I recommend using gas with no ethanol so that it lasts longer without causing carb problems.

@Bieggaoaivi 2 ай бұрын

My pilot is just to big, can i just move back to the one i had and just add higher octane gas? the one i had was just a tad to lean, and there is no pilot jet between those.

@Nate-hw1oe 5 күн бұрын

You have to tune it properly then

@usanafusion 2 ай бұрын

So i have a 2019 honda crf 125fb and when i start it after a couple seconds it starts to act like it wants to die when idleing and not getting to its full rpm and sounds very weird and slow ever since i replaced the spark plug

@MotocrossHideout 2 ай бұрын

2019, so that's EFI. If it did that only after replacing the spark plug, I would look into that. Did you use the correct plug, is it properly seated/tightened? Is the plug cap pushed down all the way onto the spark plug itself?

@usanafusion 2 ай бұрын

@@MotocrossHideout Yeah i mean all of that is done but still does it… Could it be because I used a different spark plug brand that i don’t usually use?

@MotocrossHideout 2 ай бұрын

@@usanafusion As long as it's the correct size, type, and heat range for your bike, the brand shouldn't matter.

@user-xp1rh4pv9w 4 ай бұрын

im getting hanging idle on my kmx 125 i raised the throttle needle and that made it a little better than it was but still hanging any idea anyone?

@MotocrossHideout 4 ай бұрын

Have you tried adjusting the air screw?

@user-xp1rh4pv9w 4 ай бұрын

@@MotocrossHideout yes mate its 1 and half turns out it dont have a seal and the washer whats supposed to be on mixture screw but doubt thats causing the issue

@MotocrossHideout 4 ай бұрын

That could definitely be causing it. If there's no seal/o-ring on the air screw, air can leak past and cause it to run lean and give you that hanging idle. I'd fix that and see what happens.

@__215xalbert__ 2 ай бұрын

I’m having a problem, I can rev all the way when I’m in neutral, when I’m going the the gears power band does not exist it’s like it’s hitting the rev limiter way to early

@MotocrossHideout 2 ай бұрын

Sounds like the main jet might be too rich/big. Also make sure the air filter is clean with the proper amount of oil.

@__215xalbert__ 2 ай бұрын

@@MotocrossHideout I did a carb rebuild with proper specs, before I did that I definitely had to much oil in the gas, air filter might be a tiny bit dirty

@matthewlucarelli49 2 ай бұрын

Would it be safe to assume that I'm running rich if I'm just completely lacking mid to top end power? In 1st and second it has its initial pop . Half way thru second it seems to not reach it's potential. Seems very sluggish . 22' 150sx

@MotocrossHideout 2 ай бұрын

Hard to say for sure, but it sounds like that might be right. Try going down a size or two on the main and see if it feels better or worse. Make sure the air filter is clean.

@matthewlucarelli49 2 ай бұрын

@@MotocrossHideout thanks man, your videos honestly helped my scrambled egg brains figure shit out. Figured her out after work today, running crisp !

@MotocrossHideout 2 ай бұрын

@@matthewlucarelli49 Awesome, glad you got it running well, Matthew!

@HDkillerstar Ай бұрын

My bike starts after 5-6 kicks, idles great but once warm I have hanging idle (takes a second to get back down) and then tends to bog on the first blip...high rpms are great. I am running a smaller main jet but a bigger than standard pilot jet...do i need to go even bigger on pilot?

@MotocrossHideout Ай бұрын

What bike? It could be an air leak. If it's a 4-stroke, check fuel screw o-ring is properly seated, and that the hot start isn't stuck/broken/missing o-ring. Also check carb clamps are tight and the intake boot isn't cracked.

@HDkillerstar Ай бұрын

@@MotocrossHideout Understood, when its cold it runs fine, all power bands are good except once its warm it tends to bog on that first blip, pilot circuit feels lean. Ive spend a decent amount of time rebuilding these carbs (723A Keihin on a 73 CB450). I think the O rings are good, the boots are old but dont seem cracked or anything, it could just need replacement

@MotocrossHideout Ай бұрын

@@HDkillerstar Interesting. Usually, it gets richer as the bike warms up. If there's a lean bog after warming up, that brings to mind an electrical problem. Whether it's a bad wire/connection/ground, or a bad CDI. Not saying that's your problem, but just something to be aware of.

@HDkillerstar Ай бұрын

@@MotocrossHideout understood, Ill check all the connections again...especially the coil etc. Also comes to mind this issue got worse after using 91 octane the past 2 times

@Altanabstick 15 күн бұрын

Hi! I have a 98 WR400 with a 450 carb. It did not respond to the mixture screw and did not die when fully seating the screw. I changed the pilot jet from the stock 48 to a 45 to a 43 to a 40 to a 38 to now a 35, HUGE change. Now it responds to the idle screw, 2 turns out seems best. It does not sputter when lugging the engine in high gear but it sputters bad with just a bit more revs and a small throttle opening. Wacking full throttle feels perfect. It backfires quite a bit from half the rev range back down to idle. I am confused. Can a 35-38 idle jet be right? And should I also lower the needle to remove the sputter when cruising?

@MotocrossHideout 12 күн бұрын

That sounds smaller than it should be. What is the float height set at?

@Altanabstick 12 күн бұрын

@@MotocrossHideout I lowered the needle to make it lean, and suddenly it wouldn't start anymore. I have the suspicion that the needle doesn't close off the orifice at the mid position, causing the needle to influence the pilot circuit. It started fine at idle 35 needle 0 but won't start at idle 35 needle -2 leaner. I am now at idle 40 needle +1 richer and it fired up again. Still need to ride to test whether the rich stumble has become worse or better. I have the feeling that the needle doesn't close the orifice at the mid setting, which influences the pilot circuit. Making the needle -2 leaner closes off the orifice and because of that it won't start. After I am done testing the needle +1 richer position I want to revert to idle 48 and needle -2 leaner to see if that starts and removes the rich sputter at small throttle openings. If that is the case I theorize that the needle doesn't close off the needle tube at richer settings which influences the pilot circuit by adding fuel through the needle orifice. The float hight seems to be parallel with the bowl gasket

@MotocrossHideout 11 күн бұрын

I would recommend measuring the float according to what the OEM service manual says. Sometimes parallel isn't always right, I've found. Also, if you have the stock needle, I would probably go back to the stock position and then figure out the pilot jet and fuel screw setting first because that's the most critical for starting, idle and up to 1/4 throttle. If the pilot jet is more than 1-2 sizes bigger or smaller than stock, then I suspect there's another issues causing it to be too rich or lean, if that makes sense.

@Altanabstick 11 күн бұрын

@@MotocrossHideout That makes sense. A 35 pilot does not make sense. I will check float hight conform manual tonight. Btw, just tried riding with a pilot 40 and needle +1 richer and it was a stutter mayhem, 35 and needle at 0 also had bad jitters but has been the best so far. I have no idea what my rich issue could be. Next step is a new sparkplug, checking the float height. If float height is normal I am going to try the stock needle at -1 leaner with 40 pilot, and 35 pilot, and 48 pilot. I'm kinda lost

@Altanabstick 10 күн бұрын

@@MotocrossHideout Checked float height, 8mm conform spec which is parallel with the gasket. Reinstalled everything with needle -1 leaner and pilot 48. Kicked to life without choke. Strong smell and eyes were burning. Installed 42 pilot kept needle at -1 and went riding. Starts with choke, ran best with idle screw seated and stutters at small throttle openings. Shut off after 10 mins, didnt start again and had to walk 40 mins home. Gas was flowing out of exhaust when kicking. Back home, turns out overflow is clogged, gas came pouring out of intake manifold. Seems my float needle is shaking or something and doesn't work when bike is running. Going to test with transparant tube on overflow to see gas level in carb while bike is running. Gas level right now (using transparent tube to measure) is about 10mm above gasket at the main jet. Is this too high or not? It is currently not overflowing.

@pikzzzlerkerll5247 Күн бұрын

Why does bike start only when air screw is tighten?

@MotocrossHideout Күн бұрын

As in, zero turs out? Sounds like it needs more fuel = bigger pilot jet.

@kjois6198 18 күн бұрын

So how to tune rich pilot jet ?

@MotocrossHideout 15 күн бұрын

Start with the air/fuel screw. If you want to learn how to do it in just a few minutes, grab my free guide in the description and let us know how it goes.

@williamlambie57 3 ай бұрын

My dirtbike will bog from idle if you snap it to wide open throttle.... if you easy it off idle then wide open throttle it will rev freely. Brand new carb and jets! What's going on here?

@MotocrossHideout 3 ай бұрын

Hey William, what bike? It could be the main jet that's not perfect sized, but if it's a 4-stroke that doesn't have an accelerator pump on the carb, sometimes they can't handle quick WOT.

@user-bv8mc8xj8b 2 ай бұрын

@@MotocrossHideoutI am having the exact same issue. I have a 2002 Yamaha TW200 and I just put a 28mm nibbi Carb in it with a new throttle cable. I can adjust the air screw and idle screw to get it to idle properly but if I snap the throttle wide open it almost dies or does die. If I adjust the idle screw and air screw to idle a little high then it doesn’t bog when I snap the throttle. I was thinking I need to put a bigger main jet in or can the bike just not handle 0-100?

@MotocrossHideout 2 ай бұрын

@@user-bv8mc8xj8b WOT has to do with the main jet, but most dirt bikes that don't have an accelerator pump can't handle 0-100 quickly, especially if you're just revving in neutral (not a practical test anyway).

@xxs1lentk1ller30 2 ай бұрын

I changed my pilot jet from 40 to 32 and now when i touch throttle it just dies

@MotocrossHideout 2 ай бұрын

Not sure what bike you have but that's a huge jump down (3 sizes, which is a lot for a pilot jet). Why such a big change?

@xxs1lentk1ller30 2 ай бұрын

@@MotocrossHideout thanks for quick answer, my bike is alfarad 250cc on nibbi pe30 carb i had issue when i put on choke it just died same after more than half throttle so changed it to 38 pilot better but still bad 35 better but dies a little 32 was the best but ye now this issue

@MotocrossHideout 2 ай бұрын

Gotcha. It sounds to me like the engine isn't fully warmed up because you shouldn't leave the choke on while riding. Once the engine is fully warmed up and the choke is off, the bike should be able to idle, and then you can make accurate jetting decisions, if that makes sense.

@xxs1lentk1ller30 2 ай бұрын

@@MotocrossHideout ok thank you, i tested on 35pilot and got weird issue with very hard starting and extremely high idle on choke but dies without

@MotocrossHideout 2 ай бұрын

It sounds like it might be lean. Make sure there are no air leaks (caused by loose carb clamps or cracked intake boot). I would probably try the 40 again and keep it running until the engine is fully warmed up so that it will idle and run without the choke. You may have to adjust the idle screw.

@choppergirl Ай бұрын

Nonfunctioning Carbs have turned my love of motorcycle into absolute h8tr3d. When you've taken the same one apart, cleaned it and every jet and passageway and hole and seal, put new parts in it, checked everything, 50 times and put it in and out of the bike with no significant improvement... Carbs are the worst POS ever.

@MotocrossHideout Ай бұрын

Sorry that you've had so much trouble. I replied to your previous comment on one of my other videos. What bike do you have? 4 stroke?

@germanthiccboy4139 4 ай бұрын

So if my bike is both my bike will bog and will not idle, it will can take forever to start and be extremely hot immediately

@MotocrossHideout 4 ай бұрын

Sounds very lean - either carb/pilot jet is too dirty it needs to be richened up.

@germanthiccboy4139 4 ай бұрын

@@MotocrossHideout it’s a brand new carb so should I make the number go up or down ?

@MotocrossHideout 4 ай бұрын

@@germanthiccboy4139 Richer = bigger. Before that, I would try adjusting the air/fuel screw. Grab my free guide in the description so that you can know if the pilot jet needs to be changed.

@jonathanheiny7300 13 күн бұрын

Also check for air leaks around manifold and carb