Ruled out fuel prob, ignition?????

tooth and nail · 08-28-2009, 09:59 PM

Here's the problem from previous thread(Modded Blaster jetting) runs great from idle to 3/4 , from 3/4 to WOT, it falls on it's face BAD. won't recover Here's what I got. most of which was on it when I bought it
Factory B pipe
after mkt head w/176 & 178 psi
carbon tech reeds
cone type arrester
oil blockoff
not sure about pistons or porting(haven't needed to go that deep yet)
pop off 22 psi 2.3 needle seat
152.5 main
120 pilot
tried 2 sets of plugs gaped to .25 -.32
carbs been apart many times ,it's perfect
I've ruled out any air leaks with carb cleaner
I've bypassed the fuel selector switch
I haven't changed the fuel lines , but they look like new

I still think it's lean at WOT, however I don't see how
It could possibly be not firing good under high load-WOT as it will occasionally spit and sputter if you hold WOT, RPM does not matter only between 3/4 and WOT

I don't know where to look next except to switch out the CDI.

Any suggestions

freekstyle · 08-28-2009, 10:04 PM

Too rich? When it sputters and you start backing off the throttle does it pick back up?

Yamabooeey · 08-28-2009, 10:13 PM

The main jet seems kinda big. I have written down 145 main, 120 pilot, 2.3 n/s, 95g spring p/o is 20 psi (in my notebook)

Have you tried a 145 main jet? I think you're too rich.

tooth and nail · 08-28-2009, 11:39 PM

I've been from 140 to 180 , it was 155 before I added the Carbon Tech reeds, they suggested it might be rich,155 was too rich as the plugs were black.
This ski came from FL. , I'm at 900' so the 155 would be on the rich side.On a side note, everytime I've put better reeds in a 2T I needed bigger jets. ie. more air =need for more fuel.
I' thinking of putting the stock reeds back to see if it's the reeds, or something else. It ran fine, although a little rich, before.
It will only run smoth BELOW 3/4 throttle, RPM doesn't seem to matter

Yamabooeey · 08-29-2009, 12:39 AM

Low-Speed Jet / High Speed Jet Combination - While these two jets (the smaller is the low speed, the larger is the high speed) in the internal chamber of the carb body cover different throttle ranges, those ranges are directly next to one another (along with a certain amount of range overlap). While these jets operate in the same chamber, they have very different operational characteristics. The low speed jet has the brunt of it's impact in the mid range, and delivers fuel all the way to 100% throttle. If you increase a low speed jet from a #70 to a #80, that additional increment of 10 is also present at 100% (full) throttle. This means that if you wanted to increase the fuel delivery though the entire middle and upper throttle range (all the way to 100%), it can be done solely with a low speed jet change. This also means that an increase in low speed jet size would require an equal decrease in main jet size if you wanted to retain the same mixture, as before, in the high range.

This is from GroupK. Maybe go bigger on your pilot.