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Sluggish response 1/2 to full throttle,help?

flynbryan

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#1
I've been looking back through old posts on the search engine. It sounds like this is a lean condition? Am I correct in assuming this? It did not occur until the temps dropped down into the 40's-50's. As always all help is appreciated.
 

shifting

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#2
What is the usual temp, what kind of bike? Saying that it dropped temp outside 20 degrees, you will want to go up on your main jet. Up here in Idaho we have to jump up 1-2 main jets in the spring and fall. Not an expert on jetting though. Right Andrew. :moon:
 
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Faded

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#3
Shifting,

You know enough to get you by, what more could you ask for? Here experience is the ultimate teacher, but I still manage to failed the pre-req test to Jetting 101.

bryan,

Cold weather could very well be the culprit. If everything else is in order, fresh gas, air filter, etc. then try doing what Shifting suggested and go up one main jet at a time.
 

flynbryan

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#4
I thought I was correct, I just wanted some outside confirmation. Thanks guys. I guess I'll be breaking out the jets soon.... :)
 

Rich Rohrich

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#5
This time of year lean hesitation is pretty common. Before you start changing jets it might be worth looking more closely at the problem.

If your hesitation is from 1/2 to WOT throttle then you are crossing over 2 circuits the needle and the main. Within the needle travel you will be dealing with a large portion of the needle's taper, which has a profound effect on the fuel curve.

It's worthwhile to mark the throttle housing at 1/4 1/2 3/4 and WOT and doing some snap-roll on tests under load between 1/4 & 1/2 , 1/2 & 3/4 etc. The idea being to determine where specifically the hesitation is starting from.

There is a good chance that adjusting the fuel screw and the needle clip position is all you need to add some fuel to the initial throttle opening positions to smooth the transition to WOT. Most riders spend very little time and full throttle , but tend to adjust the main first becuase it's easiest to access. Working from the bottom up will give you a better idea of which circuit is the major culprit.
 

flynbryan

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#6
As always your thoughts are appreciated Rich. Thanks. I'll try it out this weekend.
 

Faded

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#7
Rich,

Thank you for the lesson, one of these days I'll have the bottom up approach drilled into my head. :thumb: I can see how this would effectively richen the jetting across the board (for the most part) to compensate for the effects of the cold(er) weather instead of just helping WFO. :worship:
 

Rich Rohrich

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#8
Originally posted by Faded
Rich,

Thank you for the lesson, one of these days I'll have the bottom up approach drilled into my head.
It isn't the only way to do it, but in situations like this I've found it works best for me.