Need some tuning guidance

[rollin5150]

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.

[Matt_E]

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 (http://www.mikuni.com/pdf/sbn_manual.pdf). 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]

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]

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]

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.

[Shonuff]

Bump the low jet to 81.5 and see what happens.

[rollin5150]

Thanks Sho. I will give that I try soon. I am in the process of pulling the carbs to install the 80g spring.

[crammit442]

Bump the low jet to 81.5 and see what happens.


There is no such jet. They are in 2.5 increments.:reporter:

[Shonuff]

It's good to see you're not just a pretty face but in fact, useful too, Crammit.

[crammit442]

It's good to see you're not just a pretty face but in fact, useful too, Crammit.

Shonuff.......:naughty:

[Matt_E]

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?



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.

[rollin5150]

I will give that a try.

[X2Pilot]

your only problem is your pop off...too high. change your spring to an 80g black and the boat will come alive.

[Shonuff]

your only problem is your pop off...too high. change your spring to an 80g black and the boat will come alive.

I recognize those shoes.

You've got a different name over here?