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Navaho6

'09 too snappy just above idle. How do I tame it down?

28 posts in this topic

I'm using this bike for woods riding and the only real gripe I have is that it is a little to snappy right above idle. Just twisting the throttle slowly, rpms jump up so quickly, like a switch being flipped.  My WR's weren't like this.  What is the cause and the cure?

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I believe that the cause is you have a mx bike that wants to rip and power on. I don't know if there's anything that could be done to the carb that's really beneficial for that jerk. Maybe a wr tranny (did in my 04). I think your best option would be a flywheel weight.... Others might know other tricks.

Edited by billygildark5007
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So, does this engine ever pop or crackle through the exhaust on decel? If not, your problem may be that it's been set up too rich on the pilot circuit as an incorrect fix for a bog or whatever.  That can lead to a sloppy off-idle transition.  If this is your first YZ450, and you were used to a WR or something, some degree of this is just the nature of the YZ, but you should be able to get a smooth, linear transition from it if it's tuned right.

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So, does this engine ever pop or crackle through the exhaust on decel? If not, your problem may be that it's been set up too rich on the pilot circuit as an incorrect fix for a bog or whatever.  That can lead to a sloppy off-idle transition.  If this is your first YZ450, and you were used to a WR or something, some degree of this is just the nature of the YZ, but you should be able to get a smooth, linear transition from it if it's tuned right.

Thanks gray.  Yes, it is my first YZ.   I have not noticed any popping on decel.  So I guess I could try a smaller pilot. Anything else I can do?

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Check out the G2 'throttle tamer '.  Many folks swear by these.  The G2 is available with a variety of cams to slow down the initial throttle response.  Another option is to add a flywheel weight.

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Thanks gray.  Yes, it is my first YZ.   I have not noticed any popping on decel.  So I guess I could try a smaller pilot. Anything else I can do?

 

Start by finding out whether that's the problem the easy way:

 

http://www.thumpertalk.com/topic/271735-how-to-confirm-your-pilot-circuit-setting/

 

The popping thing is just an indication.  If you ignore the exhaust and set the bike up so it runs the best it can in terms of how well it idles, most YZ450's will pop "some". 

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I know what you mean...

My mates KLX450R has been race tuned by a pro... when I ride it in the tight stuff it nearly kills me because it is so instantly responsive. No issues, just wants to gooooo!

I think the throttle cam would be the first choice, then it's easy to swap out if you go into some wide open stuff.

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You could try an 08 cdi box.. There powerband (lol) was much more mellow and more manageable. They were almost considered weak. But they aren't. They are just way easier to control.

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You could try an 08 cdi box.. There powerband (lol) was much more mellow and more manageable. They were almost considered weak. But they aren't. They are just way easier to control.

08&09 cdi should be the same. Check to see if you have an 06,03 or 04 cdi Edited by Gunner354

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08&09 cdi should be the same.

 

Maybe they should, but they aren't.

 

2008: 2S2-85540-B0-00

 

2009: 34P-85540-00-00

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Maybe they should, but they aren't.

2008: 2S2-85540-B0-00

2009: 34P-85540-00-00

Does this make me right? B)

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I have a flywheel weight and a WR450F header on the bike.  I don't mind the snappy power except in 1st gear.  The bike goes from idle to revving in 1 mm of throttle travel.  I've been told that this is a YZ trait.  

Edited by Navaho6

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It's going to be more abrupt than a WR, but shouldn't be too bad unless you've geared it lower.  That tends to exaggerate it.  The early EFI bikes were a lot worse than any carbed YZF I ever rode.

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I did gear it down but that's not my main complaint.  The problem is the sudden, non-linear, light-switch-like spike in rpm immediately above idle. It was the first thing I noticed different about the YZ after coming off my WR.  

 

I hate first gear in the YZ but if I could resolve this low rpm issue, it would be a lot easier to live with in the woods.  

 

Are there any other differences between the YZ and WR other than fueling that contribute to this abrupt engine characteristic  (cams? spark?)  

 

I'm going to check the pilot jet tomorrow.  If that doesn't work, I may order a G2 throttle tamer.  Maybe this Summer I'll split her open and drop in a WR tranny.

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You could change the gearing and go down a few teeth on the rear sprocket, but then you will run into issues of too much speed.

My bike has the same problem. I just wanna downgrade to a 250 2 stroke

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