Tuning Hotaru

heya,

Ive got the tuning close, but not there yet.
Its xj550 seca, breathing through stock horns into the airbox which now has had the entire back chopped off and replaced with K&N suzuki swift airfilter.
Pilots@45, Main@22.5

Valve clearance in spec, floats in spec.
carbtune-balanced, tried colortune but cant see enough difference (struggling to build the Yics blocker)

Idles ok, lil lumpy.
Easy riding around 3-4K but lots of gurgling on decel.
Smooth accel, really takes off around 6K but then gurgles a bit around 60mph/power loss then clean accel all the way past 100mph.
Doesnt like to cruise at high speed, needs WOT or it gurgles and mucks about.
This gets worse as it warms.

I had larger main jets but spark plugs were going black.

Im confused by these symptoms.

What do you guys think?

 

#45 pilot jets are pretty large..........

 

Yeh I've gone up incrementally #40 to #42.5 to #45, trying to get a yellow/orange flame in my colortune when the screws are more than 3 turns out.
Plugs seem ok when I keep revs low, so I'm 80% confident...
70% mebbe

 

Remember that the pilot system is providing fuel at any throttle setting, it's just most prominent from idle to about 1/4 throttle. I would not be too worried about getting the yellow flame at 3 turns, but more so where the flame goes from white (lean) to blue. I would go back the the stock pilot jet, use the colortune and turn them in to get the white flame and then open them enough to get a blue flame. Then put in new plugs (so you can get a good clean reading), take a ride and read the plugs and adjust as necessary to get the proper plug color. If you have to add richness to get the proper plug color do so in tiny increments, no more than the width of a dime or even less. I'm thinking that you have the pilot jets so large that it's impacting the fuel mixture too much at higher throttle settings. However, I keep everything stock, so I have no experience with the the other modifications you have made. Good luck.

 

Hi Tabaka,

Its just not an option for me.
Consider the size of the airbox hole. my engine breathes through a hole at least 10x larger.
Stock jets make my engine fly up to 6k and stay there, hanging, because they are definitely too small.
This is the seventh hell of rejetting.

Nevertheless, cheers for responding, i'll see how lean i can get on the pilots and see how it affects my upper range.

 

I was talking only about the pilot jet. No doubt the main needs to be larger.

 

this says too rich.
as for the pilots, the air box isn't a factor at idle considering the tiny opening at the butterfly's.
maybe there's something here that might help
http://www.factorypro.com/tech/carbtun.html

 

Ok, sorry for long delay, been adjusting and testing.

I backed off the pilot to 42.5, then 40.
Each time the bogging became less of a problem, but 40 brought lean idle issues.

So im back to #42.5

BUT.
When i got the bike it had all sorts of weird jetting. Everything had been messed with.
So i had some spare needles.

I Swapping out the 4gz11 needles for 4chp3

They are longer, less of a taper and have multiple clip positions.

Omg result.
Bogging is gone, bike loves everything all the time.
Also, added an extra tooth to my front sprocket to space out the gearing.
Very happy bike.

Cheers for all your input guys, it always helps.