This is my first post and I am in real need of help. My 2006 YFZ450 is giving me grief. I have had it back to the dealer twice and I am afraid to take it back there again, they have not been much help. Here is my problem. There seems to be a dead spot in my throttle. I am not sure it is the throttle; it might be getting to much gas. While idling, if I gently rev it up it is fine. If I aggressively get on the throttle it reacts kind of like a rev limiter would act, kind of bogs down and will sometimes kill the engine. It seems to be a certain position on the throttle. If you can slowly give it gas and get past that spot, you have a lot of room left to rev up the engine and there is no problem. I wouldn’t mind if it only did it at idle, but this weekend I almost went over the handlebars on more then one occasion because of it. Let me explain. I would come to a spot in the trail where there was an obstacle I had to clear, a down tree, a rut, etc. you know something like that, I would slowly approach it, give it gas to get the front end over it, my machine would find that spot, the engine would kill, my front end would drop into the rut and I would almost fly over the top of the bars. My Yamaha dealer told me that this dead spot is normal. I ride with a pretty diverse crowd…2 Hondas, 1 Kawasaki and 1 Suzuki; none of them have this “normal” problem with their machines. HELP!!

 

First of all welcome to the forum. I hope that someone can answer your question if i cant. heres what i think it is. More than likely it is a jetting problem, i dont know much about jetting because ive never done it and dont really know much about the sizes. But another thing you can try is turning your idle up, my friend has a blaster that was having the same problem but since the rev range is so small on a blaster it was accually the idle that was the problem. Usually they come set fairly low from the stealership. It sounds like you need to take it back again and tell them if they plan on doing any more business with you or your friends that they will fix the problem with your quad.

A lot of stealerships are lazy about fixing things, take it in and tell them they need to rejet it.

P.S. you are running premium gas correct?

 

It could also be the throttle position sensor. Did they check the out put of that? Its just a variable resistor, and sometimes they get a dead spot. Have them check the out put of it, though out the travel of the throttle, or just replace it.

 

hi, i think you can fix your problem very easily. your quad is running to rich. simply turn the mixture screw located on the bottom (outside) of your carb in (clockwise) a half of turn and give it a try. I'm willing to bet it will work. if this doesn't cure it, turn the screw back and clean your carb. have a blast riding!!![img]i/expressions/face-icon-small-smile.gif[/img]

 

Thank you for your input guys! Let me get you up to date with the latest. I have been avoiding my Yamaha dealer like the plaque, I have been very unhappy with their response and attitude toward my problem. I finally broke down and took it back for the third time. I actually think they might accomplish something this time, because they had another person bring back their machine for the same reason. The dealer called Yamaha and asked them what was up. They ended up turning up the idle to 1700 rpm’s and adjusting the air/gas mixture screw. They said it took care of his problem. So, I am patiently waiting to get my machine back. I am not sure this makes sense to me, but as long as it works. I will let you know what happens.

 

if it's stock.... it is most likely water in your gas..

 

No, it's not water in the gas. I have probably went through 40 gallons by now. It must be a little more complicated then what the dealer originally thought, I just called them to check on it and they had the carb on the bench. They also said the plug was all black....No riding this weekend.

 

the black spark plug is a sign of running too rich... too much fuel for too little air. hI found that my dealer had no idea when I asced for help with jetting with some mods. sometimes you are better off just doing things yourself, which socks because they are the ones who realy should know. If you went through 40 tanks of fuel you should've replaced the spark plug long time ago, as first service is due after 20 hours. No worries they will figure it out sooner or...... better sooner[img]i/expressions/face-icon-small-happy.gif[/img]

 

Listen to 450YFZrider. Its really sounds like its the mixture. Its very simple to adjust. I would turn it all the way in counting the number of times I turned it. If it was 3 turns bring it back out 2 1/2. Then test. You really want to make small changes at a time. I go 1/4 turns at a time. Mine had the same problem this week. I played with it a few minutes and it now runs better than before.
Stay away from the stealerships, all most of them guys can do is replace a part. They can't troubleshoot.

 

My 450 does the same thing off idle if you give it too much throttle. The dealer told me that most 450's have the same problem and that its impossible to fix it completely. With my mods(cam, air lid removed and full exhaust), they put a 172 main, dropped the needle clip(raising the needle) 1 and replaced the air mixture screw(aftermarket so its easier to adjust without tools). Increasing the idle helps and the rejetting helped a little, but, the problem is still there! The dealer says that the thumb throttle opens the slide too much too fast and thats why it kills the motor. I have a terrycable thumb throttle now and 18" rear tires. With the gearing being lower(because of the smaller tires) I havn't noticed it. The thumb throttle had nothing to do with it as it done better with the stock throttle on also, but, its a little easier on my thumb with the aftermarket thumb throttle. If you want to try a different thumb throttle I wouldn't recommend terrycable as they are focking privates. If they were 2 hours from me I would have called in sick to work so I could pay them a visit. They sent extra parts with the throttle(extra cable adjuster). It didn't fit right so I called. The lady was nice, but, couldn't answer my question. She got the tech(dumbfock that works there) and he said the throttle fits the honda and yamaha and could not remember which one needed the extra adjuster. The tech was very rude like he was way too good to be talking to me and someone in the background was yelling at him that I all I had to do was put it together and if it dont fit take it back apart. With no directions(with the $124 throttle), I am an idiot for not knowing this or wanting to spend the extra time installing this $124 throttle. Terrycable,..............I will tell everyone I can about this!Text This reply ended up being long, but, hope it can help you! good luck! Guess you can't cuss. Well fock!