Need some tuning guidance

rollin5150

rollin5150

Location
Idaho
Well I have been tuning my ski after the wetpipe install for about 1 month now and am determined to get it right myself. All manuals and articles have been read and understood for the most part. I feel that I am very close but want some insight to whether I am moving in the right direction or not. My problem now is the low speed circuit. I tune the low speed adjuster at idle to max out RPM then turn back 1/8 turn. Little smoke at idle and it is smooth. Then I gun it and it falls on its face (no blubbering, just sounds exhausted and will not recover). Now if I back out the low speed adjuster I can get the throttle responce good but it smokes like a pig at idle. My thoughts are telling me that I need to lower my pop off pressure for adjusting my low speed adjuster out is covering up the lean condition. Does this sound about right?

Ski is a 07 SXR with wetpipe and K&N filters. Low jet is 80 and high is 150.5. Still waiting on a popoff gauge but have a 2.0 N/S with a 95 gram spring. According to the mikuni chart, I have a popoff around 25psi.
 
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Matt_E

Matt_E

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at peace
You have too little fuel on the low speed (not the idle adjust).
You need to either decrease popoff pressure or increase your pilot jets.
Read this. It should explain a few things.

One question: Why are you backing the idle adjuster screw off 1/8 turn after you achieve max idle RPM?
You need to leave it at max idle RPM - that's where the ideal idle mixture is at.
If the idle is too high for your likings, adjust the idle throttle position.
 
rollin5150

rollin5150

Location
Idaho
Sorry for the confusion but I meant to say that I back off the low speed adjuster by 1/8 turn and not the idle adjust. I have tried going to a larger jet and I could not lean it enough when adjusting. That was with a 90 size. I figured that I needed to go with lowering popoff now. Also could the water adjustment screws on the head pipe cause this loading up the waterbox? What is a good way to differentiate between the two?
 
Matt_E

Matt_E

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The kind of stumbling you're seeing is most likely not caused by a waterbox.

When you increased the pilot jet size, by how much did you go up? Also, did you re-adjust the idle mixture screw at that time?
 
rollin5150

rollin5150

Location
Idaho
I figured that it was not a loaded up waterbox since I can get rid of the hesitation by opening up the low speed adjuster. I did try a 90 size jet and was able to get the throttle response good with re-adjusting the low speed adjuster but at idle it seriously was smoking and not as smooth as it should be. When idle was was good and low speed set correctly, I still had hesitation when slamming the throttle. I am going to install a black spring (80gram) and see where that takes me.
 
Last edited:
Matt_E

Matt_E

steals hub caps from cars
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Location
at peace
rollin5150 said:
Sorry for the confusion but I meant to say that I back off the low speed adjuster by 1/8 turn and not the idle adjust. I have tried going to a larger jet and I could not lean it enough when adjusting. That was with a 90 size. I figured that I needed to go with lowering popoff now. Also could the water adjustment screws on the head pipe cause this loading up the waterbox? What is a good way to differentiate between the two?
Click to expand...



You went from 80 to 90. That is a jump of four jet sizes. I am not surprised that you weren't able to lean it out enough.

Try 85 pilots.
 
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