04 Yz450F sputter/popping

Hey guys,

I have a quick question. Today i pulled my completely stock yz450F out of the garage and fired it up.. Idle fine, but when i proceeded to take off it popped/sputter really bad when i was riding.. I know it sounds like jetting and it is about 10degrees colder today 48...When i put it up the other day it was fine and it was maybe a little warmer.. I guess my question is this..a few degrees make that much difference with these bikes...Its is suppose to be 60 tomorrow here in IL so im going to try it again..Any suggestions..Thanksundefined :)

10 degrees of temperature change shouldn't have that effect on the bike. I would look at what you did to the bike after you rode it last. Is the air cleaner wet from washing the bike? Did you put a freshly oiled air filter in and then start it? If an air filter is over oiled, thumpers suck so much air, they can injest the oil into the carb and plug some air passages or make it run funny for a bit. Did you get some water in the exhaust when you washed it? Check the air filter and make sure the bike is good and warm before you take off riding it and see how it does...

I have to disagree. It only takes one degree difference for water to boil. Cold weather makes my 426 spit and sputter and it doesn't take much difference.

Your jetting is to lean. Try richening the air/fuel mixture screw and play with it until it gets better. If it doesnt, try richer jets. I had a problem with mine, but it wasnt from temp, it was just from the air/fuel screw vibrating out of position.

Hey guys thanks for the input..im going to get out here and mess with it today...I will fill you in on the details...once again thank you :)

I agree cold weather does definitely have an effect on jetting, however, 10 degrees isn't that drastic of a change. If you look in your manual, it calls for the same jetting for 48 degrees as it does for 58 degrees. I'm not ruling that out, but in my experience, it isn't the most likely culprit. I have been wrong in the past, you can ask my wife about that. I'm just relating what I know in hopes of helpin' the fella out, as I'm sure you are. Now, how does your bike run today?

Hows the gas, plug?

WEll guys,

I took the 450 out today and still sputtered and popped.. Its about 53 here now...not much change from the other day. But i did turn the fuel screw out about 3/4 of the way and she is now once again a BEAST...Thanks for all the inputs...Thanks

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