2007 YZ450F - Baffled????

[RR@ARS]

This one has me baffled. I'm sorta a rookie when it comes to jetting although I've done it many times before.

All I did was rejet my 2007 YZ450F hich is totally stock (pipe and everything). I live at 360 ft. elevation (sea level). I went up one on the pilot to a 48 and up one on the main to a 162. went to start it and using the choke it started up after a few kicks. Let it idle for about a minute then tried to turn off the choke and it died. Went to restart and nothing!!!!!!!

Any suggestions before I return to the stock jetting??? I haven't messed with the fuel screw yet. Was thinking of turning it to about 1 turn out to start and try again. Is it possible I tightened the jet too much?

[grayracer513]

There are two paths to take in troubleshooting this:

> You caused it by working on the carb.

OK, but how? If you had the bowl off, it could be that you jammed the float up, and the needle valve is only allowing the fuel to fill very slowly. To see if that's happening, pull the jet access plug and turn the gas on. It should run out pretty fast. If not, fix it. Otherwise, you might as well chaeck the pilot jet for an obstruction, but there's nothing about installing them that you could have messed up that badly.

> It has nothing to do with the fact that you changed the jets.

You might want to assure that there is fuel in the bowl as above, but after that, just pretend the jets were never changed. Check for spark and for a fouled plug, and go from there.

[rexbond007]

48 at sea level, i think you flooded it. i'm at 3000, and still running stock 45.

i change to a 48 at -10 celus. try back to a 45 and still leave your 162 main in.

[RR@ARS]

Never removed the bowl. Think I'll try closing the fuel screw a little and then go to checking the plug.

[BIG HAL]

48 is good I went to a 48 here in Dallas... Did you take the slide out? Did you get a Zip Ty hand fuel screw adjuster? My screw is about 2 out..

[RR@ARS]

48 is good I went to a 48 here in Dallas... Did you take the slide out? Did you get a Zip Ty hand fuel screw adjuster? My screw is about 2 out..

That's kinda why I made the change because it felt like it was running lean.

No, I didn't install the adjustable fuel screw, but set the screw at about 2 before I fired it up the first time. Gonna have another look at it again tonight when I get home. Thanks!

[BIG HAL]

Well HMMM you said you didn't take the whole carb off right? just the access plug? Might have to bring it out to 3 turns then go back from there.. That bike does it have some pollution control?

[RR@ARS]

Nope, never removed the carb or bowl. No pollution devices that I'm aware of either.

[bwenz]

Did you turn the fuel off? If so, turn it back on.

[RR@ARS]

LOL, well I turned it off to change jets but, yes I did indeed turn it back on.

[BIG HAL]

Did you get it fixed?

[RR@ARS]

No, didn't have time last night and now leaving town for a few days so It'll have to wait until I get back. Kinda gets on my nerves though knowing it's just sitting there with a problem!!!! Thanks for the help though, will post here when I get it sorted out.

[albertaguy]

Help me out here, I've got better at jetting over the past year but am still learning. When I buy a new bike it's almost always lean for where I live which is about 3500 feet I think. The shops always say "ya they always come jetted for sea level" and/or "they come super lean to meet emmisions" so in my mind I always think of guys at sea level running leaner than me. Then I ask around to see what main other guys are running and usually end up going up one or two sizes on main and out a hair on fuel screw. (For my newest bike I just got the jd jetting kit and it worked great and was easy to figure out.) So if you live at sea level I would think you would hardly ever richen things up unless it gets real cold. Anyway perhaps you were not lean to begin with and now you're way rich and flooding. I also have the same bike and much of what I thought was "too lean" turns out to be very normal for that bike. I actually went back to stock jetting for summer temps and it works great (also added quick shot 2 accel pump cover). Describe what it was doing to make you think it was lean. Pipe turned blue? Been told all titanium ones do that, normal. Snaps, crackles and pops (small sputtering backfires) on throttle let off, deceleration, and especially going down hill no throttle under load? Apparently also normal for our bike but no other 4 stroke I've had does it and I don't have an exhaust leak that I can find. Slight hesitation off idle or tryimg to pull a bit taller gear through corners etc.? Acc pump cover fixed that for me. Just a thought but maybe you were'nt lean to start with and now you're super rich. If I was in this situattion and still wanted to richen up I would go back to stock jetting to see if it returns to normal so you know everything is working and there's no malfunction, just jetting issues. Then change one thing at a time. But that's just me and I'm no carb expert. Awsome bikes though. Best stock suspension I've owned so far.

P.S. why the lengthy post? it's 1AM and I'm up with my 8 month old boy so mom can sleep which is all she asked for for Christmas (some sleep). I tried reminding her that Christmas was over and she did get to sleep on that day PLUS I got her a new imac yet still here I am, in for what appears to be a long night. If you see that I have replied to every topic on this forum rest assured I do actually have a life, just not tonight.

[BIG HAL]

Yeah I here ya.. All the bikes come lean from the factory like you said so everyone goes bigger on the pilot and main jet 48-50 pilot and 170 main on the 06 no more popping on decell and no more red glowing pipe 2 1/2 on the zip ty fuel screw and it's good.. Popping is not normal and nor is the red hot glowing in the dark pipe.. I'll guarantee your car doesn't do it!!! The motor on our bikes are like your car except for fuel injection.. Oh and don't run corn blended fuel in it..

[SUnruh]

does your car motor spin to 11,600 rpm?

does your car motor make 160 hp per liter?

all F1 engines do pop on decel.

all F1 headers do glow.

your 450 is just like an F1 motor, but only a single cylinder.

if you want to jet it like a minivan, then expect it to drive like a minivan!

using a eddy current or waterbrake dyno with an exhaust gas analyzer will show just how far off you are.

[BIG HAL]

11,500 uh yeah as a matter of fact, had a small block 383 with N2O hit 11,000 rpm dude... as for the Dyno? What? use a 5 gas analyzer.. no the headerss on the race car don't glow red just a slight pink @ idle. Your gonna have some but not like the 450 stock.. The 450 motor is like the minivan and F1 except the F1 runs on methanol. The F1 is not the most powerful engine out there, my Camaro had more HP then an F1! 1200 HP, ran 7.50 in the 1/4 @ 187.00 MPH from a dead stop Dude if I' correct an F1 can only run 220.00 or so on a mile stretch!!! I could gear my car to do the same thing!!

[mxracer206]

Possibly got a bad jet, I recently had the same problem. Try another 48 or put the stock back in for now. I think the 48 pilot will work well once you find the problem.

[grayracer513]

11,500 uh yeah as a matter of fact, had a small block 383 with N2O hit 11,000 rpm dude... Dont get your panties in a wadd Sarah... as for the Dyno? What? use a 5 gas analyzer.. no the headerss on the race car don't glow red just a slight pink @ idle. Your gonna have some but not like the 450 stock.. The 450 motor is like the minivan and F1 except the F1 runs on methanol. The F1 is not the most powerful engine out there, my Camaro had more HP then an F1! 1200 HP, ran 7.50 in the 1/4 @ 187.00 MPH from a dead stop Dude if I' correct an F1 can only run 220.00 or so on a mile stretch!!! I could gear my car to do the same thing!! Dont run yer mouth about racin if ya can't back it up!! Can't you just get along? Counter intelligent one??

You have several facts wrong here.

To begin with, F1 engines are limited to V8's displacing 2.4 liters (147 cubic inches). Certain manufacturers are allowed 3.0 liter (185 cid) V10's, but must run rev limiters. They also are required to use fuels recognized by the FIA as gasoline, must be normally aspirated, and may not inject any substance into the combustion chamber or intake other than gasoline. They produce more power per liter than any other normally aspirated (non-supercharged) gasoline engine made. As soon as your Camaro lines up with those parameters, then you can compare it.

[grayracer513]

Help me out here, ...

If you go to any F1 race, most of the upper classes of sports car racing, or a moto GP race, you will hear 4-strokes crackling and popping as they decelerate. If you pay attention, you may also find out that some engines do it more or less than others. The YZF is one of those that tend more toward it.

IMO, any YZ450 that NEVER pops out the pipe on decel is too rich to run correctly. It will probably display a tendency to stall at low speeds on a throttle chop (particularly with an auto clutch), run rough, and shorten the life of the spark plug.

You're right in questioning the blanket statement that all bikes come lean. The fact is that if a YZ450 will run half way reasonably at sea level, which they will, then at some point before you get to 6000 feet, it's going to be jetted pretty close to right. I run both my '06's with a 45/165 combination basically everywhere from below sea level (no, I'm not kidding) to close to 4000 feet. During the winter, when the deserts are cooler, I'll bounce the main jet to a 168 or maybe 170. This is compared to the delivered stock jetting of 42/165, so you can see that I haven't really gone that far with it.

A lot of times with jetting, it's less an issue of the whole thing being rich or lean than it is of either the idle OR main circuit being out of line with each other. Read the manual tuning section on how to take a methodical approach to jetting. Perhaps return to the stock jetting and re-evaluate the whole picture. Visit the Jetting Forum, too.

[grunkthump]

I actually am starting to believe the jetting can vary from BIKE to BIKE...ie:same altitude/temp/mods etc....NOT sure why. My new 07' was WAY too rich (wouldn't even run) with a 48pj...totally stock 1k ft. and 55 degree temps...put the 45 back in and all was good!! good luck!!