YZ450F 2007 (help)

[hoard716]

I am new to bikes and I just purchased a YZ450F and I have some questions. It's all stock.

1. It backfires a lot during deceleration.

2. Seems to bog if I just chop the throttle in neutral.

3. Seems to make what sounds like a loud knock at idle....but still has power and idles okay. And maybe sounds like cam chain rattle under a load.

4. Didn't know what jetting and needle placement is necessary. ...I live in grand Rapids Michigan and the temp has been anywhere from 40-75°F. Still seems to have all the same symptoms so far.

5. And was looking at getting the big gun slip on and didn't know the carb work for that as well.

[hoard716]

Greyracer513

[DirtyMan]

I am new to bikes and I just purchased a YZ450F and I have some questions. It's all stock.

1. It backfires a lot during deceleration.

Turn the mixture screw out ( it's under the carb at the front of the bowl) need to mod a screw driver to fit.

2. Seems to bog if I just chop the throttle in neutral.

Normal

3. Seems to make what sounds like a loud knock at idle....but still has power and idles okay. And maybe sounds like cam chain rattle under a load.

I would replace the cam chain and tensioner. Cheap easy piece of mind. After that check valves so you know where everything is at.

4. Didn't know what jetting and needle placement is necessary. ...I live in grand Rapids Michigan and the temp has been anywhere from 40-75°F. Still seems to have all the same symptoms so far.

Try the mixture screw first

5. And was looking at getting the big gun slip on and didn't know the carb work for that as well.

Carb will work fine. You will need to adjust the mixture screw again.

[hoard716]

Thanks for the help!

[RockerYZWR]

The popping on deceleration is probably a lean condition. Where did the bike come from and when was it last ridden? If it was somewhere hot or high, it could very well still he jetted for that. 40-75 at your elevation makes for a lot of O2 to mix and burn - you need the fuel to match.

The fuel screw will only get you so far - idle and about 1/8th throttle. You probably need to re-jet both the main and pilot jets. There is lots of info here in the jetting database on ideas for what jets to use, but a 45 pilot and 168 main are probably in the neighborhood with a free flowing exhaust.

[hoard716]

The popping on deceleration is probably a lean condition. Where did the bike come from and when was it last ridden? If it was somewhere hot or high, it could very well still he jetted for that. 40-75 at your elevation makes for a lot of O2 to mix and burn - you need the fuel to match.

The fuel screw will only get you so far - idle and about 1/8th throttle. You probably need to re-jet both the main and pilot jets. There is lots of info here in the jetting database on ideas for what jets to use, but a 45 pilot and 168 main are probably in the neighborhood with a free flowing exhaust.

The bike was from texas. So that was my first thought of it being jetted differently

[RockerYZWR]

It is definitely worth your time to get into that carb and see what you've got. Although TX ranges from sea level to over 4000 ft, the biggest dirtbike market areas, Dallas and Houston, are about 600 ft and sea level respectively. But they get very hot there, which is why I asked when it was ridden last.

Research and read up on how to do stuff here, watch youtube videos, ask questions and don't be afraid to do stuff yourself. You probably have a lot of room for improvement with the bike.