Marvel-Scibler carb flooding

Sumerset · May 16, 2012

I have a Marvel-Schibler TSX985 on a IH 574 tractor. Gas is coming out the intake of the carb. I have cleaned the carb and replaced the needle and seat twice. Checked the float for leaks, found none. Tried a new float and same problem.Float level is sat at 1/4". When I crank the starter gas flows out the intake side of the carb and tractor will not start. The few times I got it started it ran rough and backfired out the exhaust when the rpm was increased, than died. Tractor ran well until this problem started. Any ideas? Thanks

bg/mo · May 16, 2012

You better do a compression check too, sound like you mite have other problems

old · May 16, 2012

Are the float needles the rubber tip type??? If they are then you may have to put a set in the needle before it will seat like it should. To put a set in the needle you open up the carb and drop the needle in the seat and then tap on it a few times. When done you should be able to see a ring in the rubber tip if you see that then it is set and should now seat as it should

Allan in NE · May 17, 2012

Yes Sir,

Been thru exactly what you're talking about.

Order a new carb. It's the only way out of this mess. You can overhaul it till the cows come home and still, it will never be right.

Allan

Allan in NE · May 17, 2012

Yes Sir,

Been thru exactly what you're talking about.

Order a new carb. It's the only way out of this mess. You can overhaul it till the cows come home and still, it will never be right.

Allan

PopinJohn · May 17, 2012

I had one where the hole in the main gasket wasn't open for the bowl vent. Not likely, but if you bought a universal kit, the gasket might not be punched correctly. If the bowl vent is not open, (could be clogged) the float comes up against an air pocket and can't close the needle-seat.
The ONLY way to check the float is to immerse it in a cup of very hot water. I've seen plenty that looked perfect, but when immersed the leak would show up.
It's also important that the float move freely in the hinge.
MikeShelby

Dell (WA) · May 17, 2012

Sumerset........yer float seat ain't set. You really haffta honk down on it. It is leaking BEHIND the seat. Do NOT use a common wideblade screwdriver 'cuz the WEDGE of the blade will waller out yer slots. Use a piece of broken-off hacksaw blade and visegrips. ...or... more better, gitta 1/2" FLAT-BLADE wood drill and grind the points off and use that with visegrips. Simple, eh? ........Dell

Secret Squirrel · May 17, 2012

Two things I would check, first the venturi, it must fit tight in the bowl as well as the top. Also check to see that when the carb is assembled that the venturi will not move. Time often distorts the fit. Another problem I have discovered is that the float will drag on the inside of the bowl. It can rub either way, inside or out. Assenble the carb and rock it, alternating between upside down and right side up. You should hear the float move inside the carb.

Sumerset · May 17, 2012

Thank you for all the great suggestions.
Today I took the carb to a man who has been repairing only carbs since 1953. Hopefully his 59 yrs of experience will solve the problem. He also suggested I do a fuel pressure check. He told me that the fuel pump can go bad and build enough pressure to force the needle and seat open. Any suggestions or info on fuel pressure or checking it?
The venturi seems to seat well and is tight when the carb is assembled. The float is free when the carb is turned over and back. Both floats I have used were tested in water that was first brought to a boil. I did not tap the rubber tipped needle into the seat. Carb was dropped off before I read that suggestion. As for the compression check suggestion, is the thought that there may not be enough vacuum to draw the fuel into the cylinders?
I will post what I find out so others will have it for future reference.
Thanks again for all the help.

641Dave · May 18, 2012

Is it "spitting" gas back out when it tries to run?

That's what was happening to me. Turned out to be a blown head gasket between the #2 and #3 cylinders, topped off with some valves that needed attention.

Compression testers are free to rent at your local auto stores. I think you should rule that out before spending anymore time, money or effort on the carb.

Marvel-Scibler carb flooding

Sumerset

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bg/mo

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old

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Allan in NE

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Allan in NE

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PopinJohn

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Dell (WA)

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Secret Squirrel

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Sumerset

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641Dave

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