Oliver 550 Carb

I have an Oliver 550 Serial 186 213-019. It was sitting for a spell, I took the carb off, soaked it, cleaned it up good, new gaskets, runs now, but very rich and smokes a little more than I would like. Fuel also
runs out IMMEDIATELY upon shut down, which to me means the float needle is either not seating or the wrong one. I would love to rebuild the carb, but there is no tag on the carb. It is a Marvel big bowl.
There are a couple stamps on the body. 1) 2G cast in under the carb inlet. 2) A31 stamped in on top of the mounting flange, normally covered by the carb to intake gasket. 3) 458/3? cast into the top
portion half of the carb where the float would reside.

Soooooo.....any indication on what these numbers mean? Do they signal to a TSX number that can be used to order a kit?

Something els odd.....I have had my hand in dozens of carbs over the years, but I have never seen a plastic venturi inside one. It seems like an unstable medium......

I don't remember seeing plastic anything in a Marvel carb. I' ve go a Oliver 550 I restored. The Marvel was just too worn , so a kit helped but still ran sloppy.. So I put a zenith on it and works pretty well. It had other issues so I rebuilt the engine, runs strong now. As to Marvel rebuild kits, most good kits includes several extra parts to cover the different models .

I agree, but with the length of production of the 550 model, there are quite a few carbs and potential combinations that would work. Having NO TSX numbers concerns me. A master kit is not cheap and getting it wrong sucks. (Did that on a MM RTU, drove me nuts until I figured out someone swapped the carb out with one from an 8N) I don't want to run into that again. What Zenith did you use? I would also bet the plastic venturi is from a cheap carb kit.

Sense you were able to get it apart without tearing the gasket, might go back in and look things over. The plastic venturi and lack of numbers could e an indication of an aftermarket carb. Not sure if a factory kit would fit exactly, so if you do get a kit, check the gaskets carefully. Don't replace anything needlessly, it may not go back the same.

Check the float carefully. Give it the shake test, listen and feel for fuel inside one of the pontoons. Float it in a pan of water, it should float equally, both pontoons the same buoyancy. Be sure it is straight and the pontoons are even with each other, not touching anything inside the bowl. I don't know the float level setting, but typically by inverting the top, the float should sit level. Usually there is a stain line where it has been sitting, get that level.

Look the seat over, if you suspect it is rough, a q-tip in a drill with lapping compound sometimes will polish one out. Be sure the needle seats before the float touches the top edge of the seat. The area around the inside of the needle/seat must be perfectly clean. I like to open the fuel valve and let the line flush before making the connection.

Look the mating surfaces of the bowl and cover, be sure they are flat and the gasket is compressing all around and especially in the middle.

Have you tried test running with the air cleaner disconnected? Sometimes they can be restricted in some unusual manner, mice nests, dirt dobbers...

I believe the idle mix adjusts backward on those, in is rich, out is lean. It adjusts air bleed, not fuel.

If it has an adjustable main jet, turn it in until it stumbles on sudden acceleration from idle. Then slowly back it out until it will take sudden throttle without hesitating. A single puff of black smoke is the goal.

Of course, the finest carb in the world won't make a sick engine run right. Be sure everything else is right, spark, timing, vacuum leaks, compression, valve lash, thermostat... If it's been running rich good chance the oil is contaminated with gas.

Ok, I should add a few points:
1) Compression on all the cylinders is 125+/- 5PSI.
2) Pulled the valve cover, everything nice and tight, no bent push rods.
3) Air cleaner is disconnected.
4) I pulled the carb off, soaked it, put a small parts kit in it. New float needle/seat/gaskets.
5) The old float looked like new, but was full of fuel. Had an old one that was in good shape, adjusted and put it in.
6) Fuel tank was nice and clean when I got it, flushed it anyway with solvent overnight in a power solvent tank, rinsed with alcohol.
7) Runs rich as hell.

I feel that the float needle is just letting fuel run past it, no matter what. I have an extra Marvel big bowl carb and parts that I could make work. Is that an avenue to explore rather than attempt to play with this one?

Forgot to mention, when setting the float level, turn the top upside down, float resting on the needle, Give the fuel inlet fitting the "suck test".

Sounds gross, but you'll live... Suck on the fitting, block it with your tongue. If it won't hold vacuum, the needle is not seating.

Spit!

Still thinking that going over to a REAL Marvel is a better bet long term. Thoughts?

I personally wouldn't give up that easy, but depends on what you have found.

Talking about a used original? It likelt will also have issues.

I don't know that you can still buy a new factory original, it would be expensive.

Did it run good before it was parked? If so, the carb proved itself to be good at one time. Now it's just a matter of carefully examining it to find a definite reason it's not right.

You can go into web search, find the passage schematic under images, or one close, they are all basically the same. Take it apart, study it until you understand what function each has. Trace every passage, verify each is open, every air bleed is open. They're pretty simple once you get in there. You'll want to scrape out each passage that has sat with fuel. The ethanol will attach itself to the metal. Just poking and blowing will give a false sense that it is clear. Use a wire from a wire brush or a torch tip cleaner. Just don't oversize any jets or orifices.

To verify real life float level, take the drain plug out, connect a barb fitting and loop a piece of clear vinyl hose open end up. The level in the hose will be the level in the bowl. A true flooding updraft will drip when sitting with the fuel on. A drip following a failed start, or even a few drops after shut down is normal, especially if the engine kicks backward as it stops.

Any carburetor can be rebuilt with the correct parts.

Ok, here is the current status....I cleaned up the carb again and verified that the float needle seats (it does now) and I installed a brass venturi. Starts up good and runs nice. However, there is NO power. It will drive around the yard no problem. Still barks out a couple black puffs here and there, but can't run a mower at all. 1st gear and 10" of grass just makes it want to die. Starting to think I have a timing issue. Just to verify, how does one use a timing light on this engine? Can't find a timing mark on the crank pulley or an access port for the flywheel.....Thoughts?

What venturi did you use? The venturi is sized to the engine displacement, was it the same as the original? Not sure what it should be, some research, calls to a carb rebuilder might get an answer.

As for timing, someone on the Oliver board below could probably answer. But I would guess probably 90% of tractors are timed by ear. Tractors are low compression, low RPM, so it's not a critical as an automotive engine.

Before starting, be sure the distributor is in good order. There needs to be very little side play in the shaft. Any wear in the bushing/bearing and the points will not stay set. Also check the centrifugal advance. The rotor should turn a few degrees in the direction of rotation, then spring back. If it's frozen, or sluggish to return, the distributor will need to come out, be disassembled, cleaned, inspected, and lubricated.

As for setting the timing by ear, at idle advance it for the fastest idle, then back it off until it starts to labor, then go about mid way. Take it for a test run, carb backfire and poor performance indicate too slow. kicking back against the starter, clatter under load is too fast.

Have you looked at the plugs since the run with the mower? The insulator should be light tan to white. If fluffy flat black, it's too rich. The puffs of black could be carbon burning out of the exhaust system. Once the mixture is right that should clear up.

Any carburetor can be rebuilt with the correct parts.