Brand new but ready to blow up?

[tazman7]

I just bought a brand new 2006 YFZ450- I rode it for about twenty minutes and looked down and the pipe was the same color as the blue plastics- so I thought to myself damn I better check this spark plug- I pulled it out and it was bright white- So I changed the main jet from a 155 (stock) to a 165- rode it- same thing- went to a 175 same thing- went to a 182 and it is still lean but alot better- I also switched the pilot jet from a 42 to a 45- I havent messed with the clip on the needle yet- but why do you think it is acting like this

And now it pops and farts when I get on it a little-

[250r4life]

i dont think it is your jetting.. i would check for other options
on a stock bike, your jetting cant be off that much

then why would the plug be white? Doesnt that mean you are burning a hole in the piston?

[Jekyl_22]

I have an 04' and the jetting was WAY too lean from the factory. I think that virtually everyone can agree that the YFZ is renound for having horrible stock jetting. Why? Word on the street is... to pass emissions tests or some other test like that. Makes sense... Plus, I would rather have a potent engine that was poorly jetted from the factory than a mediocre engine with correct factory jetting.

I can't really recommend accurate jetting specs for you since your engine is different (449cc vs. 439cc), but browse around on here and I'm sure you will find them.

You will probably end up (purely a guess on my part) switching out your needle for a NCVQ needle, maybe going a bit higher on the pilot, bringing the main down from the 182, and adjusting your air/fuel mixture screw to somewhere around 2- 2 1/2 turns out.

It's not like you run it lean and it automatically gets a hole in the piston either. It takes an extremely lean jetting and probably a decent amount of seat time. I'm sure others may have had other experiences with this... but I'm just speaking from my own. Just because you have a white plug, that doesn't mean you have a hole in your piston (or that it making one), it just means that you aren't getting enough fuel.

One other thing, I don't know if they fixed it for 2006, but the 05's and 04's had an electrical issue and you had to either run them with the headlights on, have your stator rewound, or buy a new rectifier. Try running it with the headlights on and see how it works out. Either way, you need to rejet. So try them both.

[tazman7]

Thanks a lot- I just took ther headlights off- Yamaha fixed the electrical problems in the 2006's so you can just take them off with no problem (from what friends say)

[jshtex]

Every yfz I have been around has been pretty lean from the factory. My guess would be to go with a 165 if you are still running the air box lid and the pea shooter in the exhaust. If not I would go up to a 168 and see how it runs.

As for reading the plug, if you search around the net you will find that it doesn't really seem to work well with the fuel we run today. Or at least thats the way it seems to me.

Our bike was checked on a dyno with A/F capabilities and even with the jetting correct the plug still looks lean.

[Fred55]

there is another thing to check and that is your float bowl level. on my yfz it was off after it sat for the winter and it was adjusted in correctly and caused it to become very lean, so i readjusted it now the right way and its running perfect and all that i changed was the float high.

[GPracer2500]

When evaluating air/fuel ratios with plug color--proceed with caution. There is so much misinformation about reading plugs for performance tuning it's amazing.

See THIS THREAD (http://www.exriders.com/vbb/showthread.php?s=&threadid=239162)

[racerxxgncc]

Originally posted by 2fast4u23
then why would the plug be white? Doesnt that mean you are burning a hole in the piston?
No it doesn't mean that your burning a whole in the piston, but just because its poping and cracking doesn't mean its about too blow up. Try going back down to about a 170 just because the pipe turns colors doesn't mean its too lean, its going to change colors all new pipes do this but if its GLOWING RED then I would worry but its pretty normal for color change. And if your going to own a high performance quad you need to learn to do maintenance on it and you can't ride it and never work on it so if your one of those people who think you can ride the crap out of your quad and never turn a wrench on it you will be out alot of money in major repairs. Good luck and have fun.

you will need to buy the NCVQ needle on the 4th notch. the needle on the 06 is non adjustable. the go with a 160 or 165 main and see what it does.

[PurePerformance]

Originally posted by GPracer2500
When evaluating air/fuel ratios with plug color--proceed with caution. There is so much misinformation about reading plugs for performance tuning it's amazing.

See THIS THREAD (http://www.exriders.com/vbb/showthread.php?s=&threadid=239162)

+1. Plug chops can be inaccurate information. All the YFZs are lean from the factory to pass emissions. Thats why the needle on the 06 only has one notch so it cant be modified. The glowing header is caused by the thin material used to make it.

Riding the bike is the best way to predict jetting, get up to 3rd gear WOT and let it decelerate, dont step on the brakes. Check for any hesitation or bogging on acceleration and for popping/backfiring on deceleration. That will tell you whats the problem.

[Iliketogofast]

Sweet. I wish I give my pipe that blue burnt look for free!

I know you've already gotten a lot of good replies on this, but I'll put in what I know in case somebody missed something.

White means hot, as in lean jetting or overheating. If you're burning a hole in the piston there will be little dents in the plug where tiny peices of metal hit it. Sputtering can usually be solved with a little bit of fine tuning with the fuel/air screw... But I don't think that's the case this time.

I really don't see how the jetting could be off by that many sizes from the factory. 155 to 182!? Maybe there's something else wrong inside your carburetor, like an issue with the float or related parts. Take the carb out and disassemble it. Check it for blocks, dirt, ect. To make sure the passages are clear, clean and dry the carb and blow into the holes and find out where the air comes out. Also check to make sure the cooling system is operating properly and that your coolant level is okay.

Also check your compression and make sure there aren't any air leaks in the cylinder. I can't really imagine most of this stuff being the issue with a new quad, but anything can happen I guess.

One more thing to do is get a new needle. If the top end improved with a main jet increase, your problem might be in the midrange jetting. I don't know about it but someone said the stock needle has no extra clip positions. You might try slotting that one with a grinder, but only if you're careful. If it doesn't sit straight it will rub on the sides of the hole that it slides in and out of and cause the throttle to stick. That would only be temporary to see if your situation improves, and I wouldn't try it without someone else confirming that it would work; I'm not sure if it will or not - I've never needed to try it.

[bullet3z]

Look you need to slow down on changing the jetting. You are going over kill with it.

On a 06, you can not adjust the needle or the fuel screw. So get yourself a NCVQ needle and a aftermarket fuel screw. Remove the plug that is blocking the factory screw and install the new one. Then since you are about the same elevation as me here is a helpful hint on where you want to be.

160 main
45 pilot
NCVQ needle, clip on 2nd position
Fuel Screw 2 turns out
I also went down to a #35 Leak Jet but that is for another days posts.
Also make sure you turn your idle up, they should be around 1,000 RPM. That will help with the bog also.

You can not do the plug chop on these 4 strokes, it just does not work.

[Octane]

I wouldnt worry about the pipe bluing. My brother put a Rath headpipe on his '04 Predator TLD and after 70 miles of trail riding yesterday his pipe is blue.