Jetting Tips on a Yfz450!!! This is what you need to know! 

Prolly why my fuel mileage sucks lol. Oxygenated race fuel can be pretty hard on seals. And unfortunately the quad sits way to much. I'll be looking into this in the spring. Thanks for pointing this out

Nice that's a good set up. You ever replace your thumb throttle for a Hondas? You won't regret it!

@@FullSpeedImpulse just ordered one ! Thank you for the videos brotha they help so much !

What was the issue with it before ?

Same

Will this setup work with a full empire exhaust on a 07? Yfz450

Yea I would bump your main up to 178 and see how it runs. 172 is a little on the light side.

I would try bumping your main jet up to a 175 and see how she runs with that

Have you tried adjusting your air fuel screw at all? Going to be way easier if you have a quick adjust on there

Definitely sounds lean. What’s your jet size?

it’s got a 168 main & 48 pilot airbox lid off

i’m at 600-800 elevation

@@FullSpeedImpulseaswell as stage 2 cams

I’d throw a 178 main in and see what it does. Make sure you dial in that air/fuel screw too.

You have the airbox lid off or on? What’s it doing now? Low/rough idle and popping on the top end?

Do you know what you have in it now for jets? And are you running a open air box?

@@FullSpeedImpulse I believe I have a 175 and 48. Factory airbox no lid hi flo filter

HMF full exhaust

You can try something around a 52 pilot with a 185 main. That’s a good bump up so should see sometime of improvement. Let us know where you end up!

@@FullSpeedImpulse I ordered and installed the main and pilot you recommended. The bike still has a hard time starting, have to hold throttle every which way to get it to start. Does seem to idle okay, not revving high like it was before. But as soon as I snap the throttle it bogs or dies. If I slowly roll into the throttle it will rev.

Okay. So first. It’s weird it won’t idle, if you mean like it keeps stalling. Now if it idling really high that would make sense. Your definitely lean. I would take your main all the way to 185. You can try a 52. Make sure you dial in that air fuel screw on the bottom too.

3rd jet is called a leak jet. Shouldn’t have to mess with that. Is it not running good with the stock jets in it now? And what’s your elevation?

Dang I heard those empire exhausts are pretty nice. Never ran one though. What size big bore you running?

Instagram! If no air leaks in the boot then you need to fatten up your pilot for sure.

@@FullSpeedImpulse your gonna laugh but my jets are stock rn 45 and 155 and I have a big gun exhaust . When I bought the quad the exhaust wasn’t welded together and when I got the exhaust welded it started the hanging idle (I think the previous owner didn’t have it welded to make it run with the new exhaust not sure ). I already got the rejet kit I’m gonna see if 175 will make a difference and 48 . My quad ran best when the air fuel screw was set at 1 if that tell you how bad it needs rejetting . Was just wondering if you would think that rejetting would fix it .

When it wasn’t welded together it ran amazing . I’m wondering if that is what’s making the quad need the bigger jets now ?

Dang. Lol. It won't hurt! So I'm curious what you welded on your exhaust. Most full exhaust systems are two pieces. And you'd be surprised but alot of them just slip on. Either way that jetting with the airbox lid off should run pretty crisp. Use a 178 if you got one. What's your elevation?

@@FullSpeedImpulse I ended up finding a gash in the boot causing air leak . Ordered a new boot hoping that will fix the problem as it should will keep updated .

I’d go 176-178 and 48 for the pilot sounds good

@@FullSpeedImpulse yeah I put a 50 pilot 175 main new rectifier and still once she gets to half to 3/4 throttle its like it's hitting false rev limiter

Also I had to jump my battery it's dead so that also could be part of my problem is just junk not enough juice to magneto

Replacing the battery would be a good start, but not necessarily your problem. I’ve had what seemed like a bad battery causing issues. But unsure if that was the actual problem. Your dirtbikes without electric start don’t have batteries. So I wonder…

We definitely got some mods on her. But the big thing is running oxygenated fuel. I'm about to pull her out storage and I'll do a video explaining oxygenated fuel. But man can you tell the difference

@@FullSpeedImpulse What kind of head work and compression do you have on it? I bet that oxigenated fuel is $$$ but worth it. These carbed yfz’s pull hard I love them.

Had a local guy do a port job on the head. Hot cams. 14:1 compression. Carbs been modified and bored out. Gytr rev box. Air intake, no filter box. Dasa exhaust. Stock bottom end and bore. Once this build pops we will go big for sure.

The fuel I run is 116 oxygenated Dragon fuel a local guy sells it. U4.4 vp is good oxygenated fuel if you don't need a high octane. Honestly once your paying for race fuel price oxygenated is not that much more. Just make sure you rejet!

Race gas

Well I would first start by seeing what jets are in your quad. I believe fmf has a chart for your fourwheeler on what it should be jetted at. Higher you are the leaner you will jet. And at elevation like that power loss is to be expected. Look into the ziptie mod. This could help on some of the hesitation.

When I say you would jet leaner what I mean is you would jet leaner then someone at a lower elevation. It sounds like you might need to go richer still possibly.

What’s your elevation bud?

You should usually be at a turn and half or so if jetted right. You will be able to tell by how high it idles. Not enough turns or too many and it won't idle. Find that happy spot. Then adjust your idle afterwards. Does it idle good and have good response?

I think you might be jetted to rich. Your elevation is pretty high and those are some spicy jets. The only reason my jets are so big is because of oxygenated fuel. I’m curious, How did you end up with that jet sizes?

@@FullSpeedImpulse even with a 200 main and 55 pilot it was still running like shit and I just checked the plug today and it is a gray color inside and almost a little darker on the outside of the plug

I would say bigger jets and maybe different clip position. The colder it is outside the bigger the jets you need. That’s why for the average person. It’s good to jet somewhere in between temps in your region so you have a little flexibility if it gets warmer or colder. What jets you running?

@@FullSpeedImpulse honestly have no clue which jets it has right now. just bought it last night. what jets do you think would be optimal to run for all year round michigan weather ?

Try a 50/180. I would normally say 48/178. But you are a little lower in elevation so you will need to jet richer

@@FullSpeedImpulse thank you how bout the needle clip. I got the ncvq as well

@jorgec1417 I would start closer to the bottom and work your way up if it’s to rich. The lower on the needle the richer the bike between 1/4 and 3/4 throttle(mid range)

@@FullSpeedImpulse i will try it out hopefully it works Thank you sir

Yep sounds like you need a good carb cleaning for sure. Make sure you have a good spark plug and a clean airfilter also.

What all is done to it? Exhaust? Open air box?

Well shoot. First thing I would say I guess is make sure all your boots are snug around the carb and intake. I assume when you say spit and sputters it sounds inoperable. Make sure your air fuel screw is dialed in good. Check your plug for readings. If all that looks good. Might have to double back make sure timing is good on the motor along with double check the valves and compression. ALSO if you messed with any of your throttle adjustments on the right side of the carb make sure you didn’t throw off your quickshot. That will cause a huge hesitation or sputtering when you try to goose the throttle quickly. Hope some of this helps.

I’d start by bumping up your jetting for the pilot and main 2 sizes. Richening it up will make it easier starting for you. Depending on how many hours it has on it. It might be time to check the valves.

Have you owned a 450 before?

Right now it has a 165 main and a 48 pilot and no this is my first 450. It’s gotten a new top end I’m guessing it’s stock.

I should mention this also when I first got it and I fixed all the electrical issues with it aka bought a new harness I got it to start and no where near idle but it would actually run if you stayed on the gas once you let go itd die and now that I’ve cleaned it I got only backfire

Try a 48/178 and see if it gets any better. That sounds super lean.

@@FullSpeedImpulse okay thanks I will let you know how it goes

Also 2 1/2 on fuel screw

I'd try bumping up your main a little bit. Also make sure the carb boot is seated correctly

@@FullSpeedImpulse ok I will try that! Thanks for the reply 👍

Rich*

On the bottom end

Running a a better exhaust would cause it to run more lean then rich. Pilot jet prolly needs adjusted. Open air box or still have the lid on?

Open air box

Yea i would say unless someone has messed with the jetting already I would say it definitely needs to be jetted richer. At elevation 800ft I always suggest around a 48/178. If you are higher you will lean those numbers out. If lower you go richer. Alot of those gytr pipes are slip on exhausts I believe. What's your elevation?

What’s your elevation?

@@FullSpeedImpulse sea level

You can try. Is it idling really high? Make sure you don’t have a air leak through the intake boot at all.

@@FullSpeedImpulse it’s idling kinda roughy like the one in your video not smooth. If I bring up idle screw then it hangs up once I hit throttle and may or may not come down unless I turn screw out a bit.

Well my main bearing ended up seizing up the crank this year. So that could I been partially my issue I had going on. Lol. The elevation you are at is a little tricky for me to give you exact jetting. Because 50 should be good for that pilot. You can bump it up a little more. But that pretty rich. What fuel are you running?

On here or my instagram. Instagram is full speed impulse

Full exhaust or stock?

6k your way up there. I would definitely start with some milder jetting then my recommended 48/178.

is the 2013 not fuel injected??

I believe they made both that year.

@@FullSpeedImpulse they made both. Carbed yfzand injected yfzr

Yes sir!

Seems like it would be lean. How’s it run?

It’s seem to run fine but definitely sounded like not enough fuel after watching this video. I just don’t want to melt something.

Throw a 185/52 in and see how she acts

Also how do you like the big bore. My motor is finally hurt. Trying to find a big bore that has good reviews seems near impossible

Man it seems okay but I’m to nervous with the tuning to really ride it and feel comfortable but overall the kit seems nice it has a ton of torque

I will say that is some sort of sign. Lol. Possibly could need rejetting. Is there anything else it does?

@@FullSpeedImpulse not really, and it’s only shot that flame 1 time after I put on the new exhaust, now it seems to be fine

I'm sure bumping up the jetting a smudge wouldn't hurt. Who knows you might be leaving some horsepower on the table running it too lean.

You cant modify the exhaust or intake without changing jetting. Not good for your motor

I definitely agree. Even if it does run its prolly leaning the motor out. Only time you can really get away with it is modified end caps or slip on since you still have the stock header restricting the exhaust partially

Try doing the ziptie mod on your bike. I do not have a video on it but many people do. It’s suppose to help. I did mine over ten years ago and it’s still good.

@@FullSpeedImpulse I was gonna do it today but you can’t on the 2012 yfz450s I tried to do it and on the right side of the carb there’s not the things that I seen in the video

@@Gio28419 this isn’t the fuel injected yfz is it?

@@FullSpeedImpulse no the 2012 yfz450r is fuel injected mines carb model

@@FullSpeedImpulse I have videos on GoPro of it cutting on it’ll do it under load basically like whenever I go to do a wheelie and pull back up it’ll die out until I let off the gas and at middle of the throttle like mid rpm’s it’ll flutter

Way bigger jets. And what’s your compression on the piston? Anything over 13:1 you have to start running race fuel.

Start with a 48/178 if your elevation is around 600ft

@@FullSpeedImpulse my elevation is 2300 and the piston is 12:1, i’ll start with getting the jets

Maybe not that big then if your that high up. Maybe a 45/172? But that’s only a guess maybe little less on the main

@@FullSpeedImpulse i’ll try 45/172 thanks for replying

Honestly I run the cheapest battery I can get from Amazon or eBay Lol. Sealed though. I don’t buy the ones you have to fill on your own.

Bump up your main jet. And at night time it’s common to see your exhaust glow. Specially on the yfz450s

Alright thanks appreciate you time I’ll try that

Is it normal for it to turn red after couple min an couple revs ?

@@liamlondonmobley well the backfiring is telling us it’s lean. So jetting the main up should help with that. Once the quad is running how it should I wouldn’t be concerned anymore about the pipe glowing or not.

The 165 sounds a little lean for my taste. And if you haven’t already clean your carb. Sounds like you could have a dirty pilot jet or passage. Also make sure your boots are sealed tight between the engine and carb.

Ok I’ll try that. Also is it a problem that my idle screw is maxed out?

That will all depend on your setup

@@FullSpeedImpulse Meant for yours, just for an Idea, i've got similar specs, just wanted to compare.

@gableroux136 I actually don’t know bud. Currently doesn’t run at all right now. Need to open her up and see what’s going on. Think the crank bearing might be bad

I honestly can’t remember. Did some google searching and found someone I liked and sent it out.

I’m honestly not sure. Prolly whatever Yamaha recommends because I have never tried changing the heat level of the plug

Is there a reason why you don't have electric start?

@@FullSpeedImpulse purely because I like having the ability to have a back up to if the battery dies I have had a few starters die on me

Gotcha. Is that air box lid on or off? And what's your elevation?

@@FullSpeedImpulse currently on and I'm at sea level

Well taking it off will definitely open it up. But you will definitely have to jet bigger for sure

Do you have it turned maybe a little to far to get the bike to run right? And are you sure the spring is still on it?

@@FullSpeedImpulse nope, 2 turns. I have checked and checked. And checked again. I bought a new screw I think the spring is gone, wore out, or broke

@@FullSpeedImpulse so I took the carb off, and some idiot thought it was a good idea to use a fuel screw without a spring. Bought it with an aftermarket screw

Well that’s a easy fix at least! Lol

@@FullSpeedImpulse haha yeah, I sacrificed a pen and cut the spring to a feasible length. Seems to be a lot tighter now

Anything aftermarket done to it?

@@FullSpeedImpulseall stock but i just put on a evo r slip on

@@edwardrodriguez8846 ooo yea. Time to put some bigger jets in her. You could try a mild bump up in jetting 42-45 pilot and a 172-175 main. If your not against it, good time to remove that airbox lid since your rejecting anyways. You’ll make a noticeable difference in power if you do.

Running 116 oxygenated but dang you ain't lying. Also just looks like it's from the bowl drain screw or somethin. Getting ready to get her back out here soon so I'll be checking that out for sure. Lol

Hey! I can try my best. What do you have going on?

@@FullSpeedImpulsei think it’s the carb! I bought It and the choke screw is messed up, I’ve seen another yfz carbs and it does not look like mine!

First when you say the choke screw do you mean the idle screw(its a knob) or the air/fuel mixture screw? Can you see if it say keihen on the side of the carb? Any motor work done?

@@FullSpeedImpulse would you happen to have a email or so…? Would email you some pics! The quad is currently in my hometown I bought it there, I’m currently in the states!

Man I don’t know. If you haven’t changed anything on the bike and now it isn’t running right. Your prolly past jetting. What is your bike doing now?

@@FullSpeedImpulse it’s turning and will turn on and idle and shut up and then it will just turn but won’t turn on and it killed my battery so im clean the carb and stuff but i just got the bike it’s a 2004

@6.2pushinP okay. Know anything about the bikes history? Last time rebuilt?

@@FullSpeedImpulse i do not said he is second owner didn’t say anything got rebuilt bike was riding good for the weekend the just bogged out in the middle of the ride then turned back on few minutes after rode off and then turned off

@6.2pushinP we’ll go through the easy steps. Like you said clean the carb. And check for a good spark too. Hopefully it’s something simple. Let me know what you come up with!!!

Zbroz a arms. They are pretty nice.

I believe they are not insanely expensive either

@@FullSpeedImpulse I’m looking at full fights for the price

@@Rylenstacy I’ve actually owned those before too

They are okay. Are you doing long travel?

Well for around here it’s below the average riding temp, making it cold for the quad.

Not from that. But one of our projects we've had in there for sure.

@@FullSpeedImpulse you can see it dripping from the carb

Hmmm idk. I'll have to take a look at that then. I thought you were talking about the spot on the ground. Could be a dried up seal on the carb. Does not get ran enough that's for sure.

You run bigger jets with oxygenated race fuel. Also e85. I had smaller jets in it and it was popping idling super high shooting flames out and wouldn't even rev all the way out. With the fatter jets she's way happier. Just have to sweeten up the bottom end a little.

The issue is I rarely ride the quad so don't have a lot of dial in time with her. I built her from just a frame about 5 years ago now. There's a long story behind all this but long story short I won't ever sell it. Lol