QD-11 Running Way Too Rich, Low Speed Jet Problem

[Stewart Mayer]

Hi,

I’m fixing up a Johnson QD-11, it has an earlier carb design than most 50s models.  It is running way too rich, and even runs at high speed with the high speed needle completely closed off.  I placed my finger on top of the high speed jet to make sure it was closed off and the motor still ran at high RPMs just fine.  I have double checked all the seals in the carb, and ruled out the high speed jet as the problem.  I think the low speed jet must be dumping enough fuel for low and high speed operation.  It is very different than most low speed jets I’ve seen other OMC carbs.  I can adjust the low speed to idle great, but the low speed jet seems to be dumping too much fuel in at high speed.  In the photo I’m pointing to where I think the issue is. Does anyone have any advice about how to get this under control?

FYI, the photo of the jet and carb not on the motor is from a second powerhead i purchased for parts, the carb on the motor has been fully cleaned up.

Thank you

[JACQUES]

got  the bible ?? see pages 117 -122 QD carb   operation… info may help

free download… store-print locally

https://www.socalaomci.com/library/johnson_service_manual_10th_edition.pdf

Joining AOMCI has priviledges 🙂

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Stewart Mayer

[Buccaneer]

Some carbs need a big donut gasket / washer to seal off the
bottom of the fuel pickup from the float bowl.
If the donut is missing, it will suck way too much gas.

Prepare to be boarded!

1 user thanked author for this post.

Stewart Mayer

[JACQUES]

here is a qd1o  file in case it may help… I don’t have the qd11

if the LS needle  tunes the idle fine it is unlikley it would “dump” excess fuel …At HS the throttle plate is open wide  and the idle cct is less subjected to crankcase suction  and contributes  less  fuel  which in theory the  engine then  draws the fuel supply from  the  HS section.

 

has suggested  make certain no parts are missing   (see parts listing on the QD 10 .. carbs look similar)

Joining AOMCI has priviledges 🙂

1 user thanked author for this post.

Stewart Mayer

[Stewart Mayer]

Thank you, I’m reading it now 🙂

[labrador-guy]

Stewart make sure the little doughnut gasket is in the carburetor between the float bowl and the main body.  It goes around the main jet.

dale

[Matthew Pieklik]

If there is a carbon seal seal on the crank, make sure it’s not cracked.

[Author]

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