Back ground: Traded for an 04 YFZ 450 in November, did a day trip a month ago after putting some tlc into the machine changeing oil, cleaning air filter, setting shocks, adjusting valves and such. It ran very rough, but chalked it up to being old gas since it was in there since December and the next tank of fule it ran great through all throttle positions.

Went riding this past weekend and put on a 110 miles Friday with no problems what so ever, and the miles were anything from full out throttle to chugging along at partial throttle to keep rpms down.

Saturday, cleaned air filter, and warmed it up to check oil before heading to trail. While idleing it ran out of fuel because I did not have my fuel valve on. after that it ran crappy all day. It would break up reall bad trying to give it gas. Off idel it was fine, then midrange it would spit and sputter finally catching on at about 1/2 to 3/4 throttle just to break up again if i push past it.

This is similar to the way it was acting a month agao with the bad gas, however I do not think it was bad gas since my buddies Raptor had the same gas in it and his ran fine.

So after the long post, does anybody have an idea on what is causing this. I am going to pull the carb and clean it, but is there anything else I should look at?

Thanks in advance and I appreciate any help you guys can provide.

 

maybe the float is sticking?????

I think I would also clean out the gas tank. Who knows what crap may be in there and the filter that is in your tank/petcock may be partially plugged. Take the tank off then remove the petcock and clean the filter and anthing left in the tank should be rinsed out with some gasoline.

 

Thanks, that is what I was thinking, so I feel good about that. I don't have much experience with this model yet, so I did not want to overlook anything.

So what is the story behind your avitar picture? Looks grusome.

 

Cleaning the float bowl is a good start towards fixing that problem. I replaced the needle valve on my brothers '04 because it was giving us a hard time with sticking floats and an occasional mid throttle hesitation and that solved the problem. Similar symptoms to what you describe, but not so severe. Pretty sure the previous owner had let her set with untreated fuel at some point.

 

How much was the needle valve?

 

To much. I ordered it through Bike Bandit, but every online store and dealership I checked was within a few dollars on price. You can get current pricing by using the microfilm feature either there or at Ronnies Mail order, etc.

 

Thanks for the heads up, I hope I can just take care of it with a thorough cleaning.

 

As an update, a guy over on YFZ Central said that he was having the same issue as well as others and he took the air box lid off and it has not happended since. So it sounds like a jetting issue. I will thoroughly inspect the fuel delivery system as well, but if it checks out I will try it with out the lid on and see if that helps. If that helps than is is a jetting issue and will have to spend some time with jets and plug chops.