Super Jet Noob Carb Tuning Help!

[icecoled007]

Alright, so I think I am understanding this carb tuning stuff better and better each day. I am on a completely stock Superjet (no motor mods at all) so it shouldn't be too hard.

When I first bought my Superjet idol-1/4 would hesitate - I am assuming this is what a lean hesitation feels like. So I rebuilt my 15 year old carbs (looks like they were never ever touched paint was mint), didnt touch anything, and tried again. Same setting I would still get a hesitation and my plugs were white.

I put new plugs in, and was told on here that tuning by plugs is a waste of time. I fattened the low needle up and finally got rid of the hesitation. I ended up turning the low needle about 1/3 turn...alot.

Then I put new bars and a UMI throttle on. I would go out and it was idleing really high. I assumed my new bars messed with my idle. I turned my idle screw down. Then I went out riding and noticed it would die when coming from high RPM to idol. I assumed I turned it down to much so I started increasing my idle.

I now learned that messing with idle, will mess with my low speed. My question is from here should I lean my low speed....but if I do that then I will decrease my idle.... I guess I am unsure of the ratio of idle adjustment-low speed adjustment and how much one effects the other.

Yesterday, I leaned out my low speed and it was riding fine, but sometimes it would die coming from high RPM quickly to idle (falling off after jumping wake)....is this an issue of high speed needle? I don't have alot of experience but is this "bogging" out at high? Or is that an issue of bogging out at low? Or is that some other result of too much fuel sitting in the carb


Last question.... I am running stock setup 130 main and 70 idle and I measure my pop off on both carbs - 18 psi. Since I am running at a high altitude 5280 ft should I want a lighter pop off? I am just thinking low air density = lower pop off? Kind of like aftermarket flame arrestors = lower air density from stock = lighter pop off.


I wish I had a perfectly tuned stock Superjet at this altitude to compare too.... just learning, sorry for my noob dumbness. uppy_dog_eyes:

 

[aramis]

first things first, get your throttle cable slack right. If things changed because you changed bars/throttle, your cable is too tight. As in, it's holding the carbs open and/or opening up the carbs when you turn the bars. Sounds silly, but I've seen it happen a bunch of times. Take off the hood, and watch the carb wheel as you turn the bars left to right. If it moves at all, you need more slack at the the throttle lever. Fix that, then go from there...

 

[icecoled007]

first things first, get your throttle cable slack right. If things changed because you changed bars/throttle, your cable is too tight. As in, it's holding the carbs open and/or opening up the carbs when you turn the bars. Sounds silly, but I've seen it happen a bunch of times. Take off the hood, and watch the carb wheel as you turn the bars left to right. If it moves at all, you need more slack at the the throttle lever. Fix that, then go from there...

Got r fixed.... moved the UMI lever in a bit

 

[john_650sx]

you need to get the tension on the inner cable right, just moving the lever wont alter the cable tension - adjust it with the adjuster nuts either on the lever or on the cable bracket at the carb/inlet...

 

[onedumbtrucker]

You get 18psi on stock carbs? Are they the dual 38's? I was told stock is 55psi (1.5mm N&S, 115g spring = 55psi).

Yes lower air density (higher alt) will lower manifold pressure and so you will need a lower pop-off but I couldn't tell you how much lower.