Johnson 120 VRO Plastic carbs??

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mike91695

Cadet
Joined
Jun 16, 2008
Messages
28
I have a Johnson 120 VRO I think its a 1985 ( model # J120TLC08 ) that I have been trying to get the idle to come down on. I have done the lync n sync with the factory manual 3 times with no luck. I have checked all the butterflies to make sure there closed. The roller is not touching the cam. The engine idles at 2000 RPM's when the timing is set at 3-5 degrees BTDC. The only way I can get it to idle down is to retard the timing to 6-8 degrees ATDC. Which makes the engine start hard and run rough at slow speeds. I have seen on this forum that the float bowls have changed to aluminum. Did they change the carbs as well? I have the plastic carbs on mine and it looks like the passage ways are deformed? By the way I have cleaned the carbs and put new floats and needles in them with no change. The motor runs great once it gets above 2500 RPM's. Thanks for any help you can give me.
 
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mike91695

Cadet
Joined
Jun 16, 2008
Messages
28
Re: Johnson 120 VRO Plastic carbs??

I did this timing procedure before with the same results. I did clean and check all of the low speed jets. They are stock according to my local dealer. They are 1.0 does that sound correct? My dealer told me he could not get different sizes. Is this correct?
 
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R.Johnson

Rear Admiral
Joined
Sep 24, 2003
Messages
4,446
Re: Johnson 120 VRO Plastic carbs??

The slow, or intermediate is #43, or .043. The idle air bleed is #14, or .014. The high speed is #57D, or .057. In outward appearence the C, and D jet will look the same, they are not. You must use the D. The top half of the carb will hold the Intermediate, and idle jet. The top is #43, the bottom #41. The bottom half of the carb has the high speed, #57D. You need the OEM manual to sync this engine. They don't list the Idle timing, the idle is set with the idle set screw with the engine in gear in the water with the air box cover on. You must follow this procedure from front to back exactly for best result's. When you have this engine running, the jet's in the top carb half are exposed. Stick a tooth pick in each jet,one at a time, and listen for a change in the engine. There should be one.
 
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