A whistle a 1/2 to wot

[Mike m]

I pit in 120 main jets this weekend now I'm getting a whistle at 1/2 and wot,carb synch needed?

[Flynt]

I pit in 120 main jets this weekend now I'm getting a whistle at 1/2 and wot,carb synch needed?

Typically a vacuum leak.  Check boots.

Beyond that, we'll need more information...

Frank

[Mike m]

My intakes are new.I run unipods,I'm running 42.5 pilots,idle  mixture screws out 2-3/4 turns,needles lifted 2 shims,valves adjusted last fall,brand new needles and seat,floats measured 117 mains were lean but OK,120s are fast but getting a whistle and surging sometimes

[Mike m]

I do have a after market black widow header collector and ss70 delkevic slipons free flowing exhaist

[Pat Conlon]

...but getting a whistle and surging sometimes

I know about surging...my float bowl vent hoses were obstructed.
I put longer hoses on the vent T's and they ended up hanging down too low touching the top of the exhaust collector box and melted shut....oops
I thought I had a tank venting issue, but the surging continued with the tank cap open. Lesson learned.

Mike, go to your profile and put in your signature line the year FJ you have.... Help us help you.

[Mike m]

86 fj1200

[FJmonkey]

The only change you made was installing 120 main jets? And it did not do this before the change? Then something related to the change it self or the work required to do it is causing the new noise. Does the noise happen at speed or at an RPM range while sitting still?

[jdvorchak]

Let me try to understand. First you said all you did was to install larger mains. Then you mention that you shimmed the needles. During the main jet swap? First thing that comes to mind is that you had the slides out and when you put them back in you misaligned the diaphragm on one and now it's whistling. That might also lead to the surge.