88 Carb Help Needed

Kerwin · May 16, 2023

Have an issue with the carb on my 1952 Oliver 88 RC. Last fall, the tractor started to run very rich and would actually flood out and be hard to restart. I was pretty much done using it for the season so put off fixing it until Spring. Same problem when I started it up a few weeks ago. Enough gas coming into the carb that it was flooding into the hose from the air cleaner. I don't leave the sediment bowl valve open, so gas is coming in when trying to start/run engine. Figured that the float or float valve was having an issue and bought a basic kit with new float, soaked the carb and replaced the parts. Engine is still running rich, perhaps even worse than before, and adjusting low idle and high idle screws does not do anything to help it.

I've rebuilt other carbs before and not had them work worse than before the repair...Any thoughts on what else might be going on inside? It's a Marvel Schebler TSX-374.

scootergmc · May 16, 2023

Does that model have the adjustable main needle? Those little o- ring packings can go bad but don't lead to flooding bowls. You problem is definitely float and valve related I would think. Did you try the clear tube method for adjusting the float height? Yeah it's a bit more tedious but the outside view of what's going on inside can be very helpful.

DanielW · May 17, 2023

This probably wasn't your original issue, but maybe when you did the first rebuild the float got tweaked slightly? A lot of carbs (some M&S seem to be the worst, but I've seen I on a Zenith too) have very little side-to-side clearance between the float and bowl when assembled. When you're setting the height it's easy to accidentally bend one of the floats the tiniest bit sideways, and it will rub on the side of the bowl and cause it to stick/flood. Hard to diagnose, as you can't tell when it's apart.

Best way I've found to diagnose is (with fuel off, carb assembled on tractor and drained) stick a wire up through the drain plug hole and use it to push the float up and let it fall down. Do it several times, listening and feeling. Any resistance at all or slight scrubbing is too much. Very hard to fix as it's trial and error: Disassemble, tweak a tiny bit, reassemble, test, repeat.

This post was edited by DanielW on 05/17/2023 at 05:08 am.

Dieseltech · May 17, 2023

Try setting the float gap at 5/16 instead of the 1/4 inch spec called for. That's what I use on MS carbs anymore and have better results.

J.Wondergem · May 17, 2023

Make sure the air vent in the carb is open.

Kerwin · May 17, 2023

Is that on the bottom of the carb, in front of the drain plug?

chucksoliver77 · May 17, 2023

sometimes the top of the plenum rusts through letting the exhaust in the intake. you can fix this by taking the exhaust and intake manifolds apart and put a sheet of copper between them. just snug them up a little before you put them back on the engine, once you tighten the manifold to the head then then you tighten the 4 bolts that hold manifold together BTDT

J.Wondergem · May 18, 2023

(quoted from post at 09:01:59 05/17/23) Is that on the bottom of the carb, in front of the drain plug?

No. I believe on that carb it's above the float on one side of the venture in the float cavity.

88 Carb Help Needed

Kerwin

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scootergmc

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DanielW

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Dieseltech

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J.Wondergem

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Kerwin

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chucksoliver77

Well-known Member

J.Wondergem

Well-known Member

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