40hp Johnson 1963 Carb Question

[crosbyman]

usually you can test the carb float but blowing air in while the carb is right side up and then…. flipping the carb upside down the inlet needle should block any air from coming in (simulating a full carb… mucuh like a toilet bowl inlet needle closes the water when full)

the float must be installed correctly and parallel to the carb body when held upside down (closing the inlet needle as if full of fuel when right side up)

Joining AOMCI has priviledges 🙂

[fleetwin]

Jay-
That crazy low speed needle bushing on these carbs is a real pain in the rear end! Don’t know why the carb is manufactured this way, but it is. The white washers and packing should be enough to hold that silly threaded bushing from turning, but you never know. It is possible that the bushing is spinning inside the carb body while turning the needle, so moving/turning the needle is really doing nothing. Can you gently turn the needle in until it gently seats in the carb body? If not, the needle and bushing are just spinning inside the body, you may have to tighten up the packing nut some more. Once gently seated, back the needle out about 1.5 turns. Did you remove the core plug that covers the idle mixing pocket where the low speed needle works in the carb?
If not, it is possible that debris from the messed up needle packing got into the mixing pocket while you were cleaning out the old packing, this could cause idle problems by plugging the air/fuel ports in the carb body.
So, the engine will only start with the choke off, and runs poorly. Does the engine sneeze/cough, or just chug like it is overly rich, I guess it sounds rich from your description. The engine is lean is it sneezes/coughs. You would see fuel dribbling out of the front of the carb air inlet if the carb was flooding. Did you have the fuel pump apart? If so, perhaps it is leaking internally allowing fuel to spill into the crankcase through the pulse line. You could remove the pulse line from the fuel pump, then have an assistant pump up the fuel bulb, no fuel should spill out of the fuel pump pulse line nipple.
Your description of the throttle linkage sounds normal. The shift interlock linkage will prevent the throttle from being advanced too far when the engine is in neutral, which is what you described. And yes, once in gear, the throttle linkage will "snap back" from WOT when released to about half throttle, this is normal as well. Did you mess with any of these linkage adjustments? The carb’s butterfly must be "synchronized" to the ignition system or the engine won’t idle properly. Everything is probably OK if you didn’t attempt to alter any of the adjustments and got all the carb linkage pieces back together properly.

[twsnagel]

Hi everyone:
Thanks for all your suggestions! I feel that the idle needle is properly installed now. But the engine still won’t start properly.

I’ve tried a number of things since I last updated. I initially thought my ignition/throttle sync was off – it was, but it didn’t help the problem.

The engine seems like it is WAY too rich.

I can’t start it except on ZERO choke, and when I crank it, gas pours out the carb throat during cranking.

In keeping with the stuck float idea, I connected up the gas tank. With the bottom screw plug out of the carb, I am able to use the primer bulb to pump substantial amounts of gas out the bottom of the carb. When I put the plug back in, I can’t pump any gas out of the jets in the carb throat. This tells me that the carb float is NOT stuck. Right?

I guess I’m going to have to take the carb off again. I suspect the idle air intake might be blocked? It’s the small passage at about 2:00 at the edge of the air intake, right?

Fleetwin – you mentioned taking the core plug off the idle needle area. Scares me a bit – How do yo do that properly? I do have a replacement plug from my carb kit but I’ve never done that.

One last question – the old float needle was different than the new one in the kit, but the float was the same. The new needle did not have the rubber tip, and it had a notch around the "float end" to take a retaining clip. I didn’t see how the retaining clip worked with the float and omitted it since the last needle did NOT have a notch, (and by extension, no retaining clip). Big mistake?

Thanks all,
-Tyler

[twsnagel]

OK, a new theory: The reason it will only work when it’s not choked is that the idle circuit is completely clogged. The idle jet is the only one that gets air when the butterfly is closed, when the choke is open there’s enough air to sometimes make up for the massive amount of gas coming up the high speed jet. Right? Right?

I have a feeling that welch/core plug needs to come out of the top of the carb to get it clean. It seems scary to get out.

[fleetwin]

Did you check to see if the fuel pump was flooding the engine?
I understand being nervous about removing that core plug. Maybe just use a hand drill and slowly bore through the core plug with a 3/16" bit, stop once the drill starts to break through the bottom of the core plug. Slide a small punch through the hole then pop it sideways, the core plug will pop right out.

[twsnagel]

How do I check to see if the fuel pump is flooding the engine?

I might go after the low speed jet with a can of carb cleaner and compressed air tonight before I tear the carb right off the engine again. Failing that, I’ll pull it off and try the core plug.

[fleetwin]

The fuel pump has an air pulse line running from the metal fuel pump to a port on the engine block, correct? I’m assuming this engine does anyway.
Simply remove the air pulse line from the fuel pump, then have an assistant pump the fuel bulb. If fuel comes out of the pulse fitting on the pump while pumping the fuel bulb, then the pump is NG, has to be rebuilt.

[twsnagel]

Fuel pump is good.

I tore the carb off again last night, cleaned it again, removed all the core plugs, cleaned it again, reassembled it.

Nothing. It still doesn’t start right.

When I crank it on "choke", liquid fuel builds up behind the choke shutter and then runs out if I open the choke after cranking.

I’ve checked the spark – it’s good and bright from both cylinders. The wires are not reversed.

I will try new plugs tonight just in case something is strange.

I do have a question – Do I have a part missing? This is an RDS-25D and has the fixed high speed jet. When I take the "drain plug" out of the carb bowl, I can see brass in there but there is no screwdriver slot as the manual says there should be.

Is there a need to pull the flywheel and check the points if I’m getting a good strong spark? I don’t have the correct kind of puller so I’ll have to go shopping. What size bolts are in the top of the flywheel?

Other than that, what on earth could be wrong? I’m so close to scrapping this boat.

[fleetwin]

Well, it is normal for fuel to puddle behind the choke butterfly, during cranking, especially if the engine does not start, the fuel will spill out of the carb once the choke is opened as well. Maybe the choke is working a little too well, flooding the engine during cranking, then it must be shut off/opened up to start the cold engine.
Does the engine idle OK now once it is started? Did you see any debris in the mixing pocket when you had the core plug out?
Perhaps you can make a video of the engine starting/flooding/running. I would not attempt to get that flywheel off without the correct OMC puller. Using aftermarket pullers/hardware can result in broken hardware, injury to you, and damage to the flywheel/crankshaft.

[twsnagel]

No debris in the core plug areas. If some fuel puddling is normal then maybe there was never an issue with the carb, although there was a ton of gunk in there.

I will try new plugs tonight but aside from that, I will pull the flywheel and check the points. I know the engine has new coils.

I don’t have the right puller. I need a "harmonic balancer puller" right? I have a 3-jaw gear puller but I can’t get it to hook on the edge of the gear. And I’ll have to buy 1/4"-20 bolts to thread into the holes, right?

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