Lean down idle circuit

[Lump]

How do you lean down the idle circuit on a 89 GT 150? I thought on the earlier models you just changed the low speed jets . The way Im understanding the manual what use to be the low speed jets are now the intermediate and now there is a low speed air bleed. Would you just go up on the air bleed? This thing loads up like crazy when idling aroung lookind on the sonar. I have been through the carbs and every thing is squared away. Fresh powerhead. Forgot to mention, VRO is disabled
Thanks
Lump

 

[Lump]

Re: Lean down idle circuit

 

[tashasdaddy]

Re: Lean down idle circuit

your carb has only 2 sets of fixed jets, not adjustable. it sounds like your float needs adjusting or the low and high speed jet got switch on one carb. low speed jets should be marked No.33, high speed No. 56C.

also decarbing the motor could do wonders. also time to replace all fuel lines with alcohol resistant lines.

 

[Lump]

Re: Lean down idle circuit

Thanks tashasdaddy,

I will check and double check all you mentioned. The hoses are all new and the I just rebuilt the power head has about 10 hrs. on it. What about going down a size or two on the low speed jets?

I appreciate the help
Lump

 

[tashasdaddy]

Re: Lean down idle circuit

less fuel less lub, want to rebuild it again?

 

[rodbolt]

Re: Lean down idle circuit

actually that old crossflow carb uses 6 fixed jets on each carb,two main jetslocated behind the screw plugs and horizontal at the bowl bottom, 2 intermediate jets located in the bowl mounted vertically,bowl must be removed for access, and 2 low speed air bleeds,orifices, that fine tune the amount of air when the shutters air closed. idle fuel is fixed via a dip tube.
before I started playing with idle air jetting,located at the top of each carb throat, I would double check my link and sync adjustments and check all the recirc check valves for proper operation.
but its amazing how low and smooth you can make a cross flow engine run by playing with the idle air jetting.
bigger orifice,more air leaner run,smaller orifice less air richer run at idle.
its normal to have to richen the mix a bit to correct a lean sneeze but not normal to have to lean it.

 

[Lump]

Re: Lean down idle circuit

Thanks rodbolt,
I went back thruogh the carbs and everything looks to be spot on. I will check the recirculation valves and see if there working properly. I guess if they are ok I will go up one size on the air bleeds.Motor has no signs of being lean on idle circuit, never sneezes, and smokes like a crop duster.

Thanks for the help
Lump

 

[tashasdaddy]

Re: Lean down idle circuit

have you done a decarb?

 

[Lump]

Re: Lean down idle circuit

Haven't done a decarb. Just rebuilt the powerhead. New pistons and rings. Heads were also cleaned (in a vat). Is that what you mean by decarb? I dont know why it's so fat at idle. The motor is not poked way down in the water either. I have gone through the carbs 3 times and all is right.

Thanks
Lump