Jetting........

[skippy]

Ok so my new yzf450 runs great and pulls super hard, Starts first kick and I couldnt be happier........except if I am just cruising barely above idle it kind of sputters slightly its hardly noticeable and just enough of an issue to bug the hell out of me.

The bike is bone stock with a Two brothers pipe. What are you guys running for jetting in your yamaha 450s?

Thanks for your help

 

[Caleb]

That could possibly be by design. I know it sounds odd, but atleast on the WR450s, there is a sputter "built-in" to help with cooling. I don't know if it applies to the YZs as well. You can read some more on it here: http://jdjetting.com/html/faq.htm#7

 

[skippy]

It feels like that could be the issue, It doesnt stutter at all when you mash the throttle it just flat out gets with it

 

[Gravy]

mine does this too, well not quite the same.
not bad, but just off idle it has a bog if I crack the throttle open real fast.

 

[Caleb]

mine does this too, well not quite the same.
not bad, but just off idle it has a bog if I crack the throttle open real fast.

Yeah, that's a bit different. The stutter is noticed when holding just a small amount of throttle. Something with your jetting is probably off if you're getting a bog when you crack the throttle real fast. Could be your accelerator pump.

 

[glockman]

I run a 158 main on my 08 and the rest is stock. It runs great. I drop to a 155 for high elevation (9000 ft) and it also runs great. Other than that I just turn the fuel screw for temp changes.


Sent from my iPhone using Tapatalk

 

[B2-Bomber]

if your sputter is occurring at the throttle position that you are mentioning, it will be a combination of fuel screw, and needle. this is a carbureted bike right? not a fuel injected 450?