M carb float issues

Dick Binfield · Nov 21, 2010

I recently put a kit in my M carburetor(IHC). I soldered a tiny hole closed on the float and set it to the specs according to the measuring device in the kit.Initially it ran pretty decent but recently would not start.The float hangs up because the bowl fills with gas and runs into the tube of the aircleaner. What can I do to the float to keep it from hanging up in the bowl besides may buy a new float? It does have some wear in the pin and the pin bracket. That could be some of the problem.

Dave H (MI) · Nov 21, 2010

Sometimes you just got to break down and get a new one. Are you sure it is not the needle and seat? Sometimes there be a break in period OR you maybe didn't think to clean upstream and got some crud in the seat. I have also had some trouble on some kits with the new needles but usually it is the reverse...getting them to come OUT of the seat. Just some ideas.

Dick Binfield · Nov 21, 2010

I did install a new needle and seat.I used carb cleaner and blew it out with air and pressurized kennesol(like brake cleaner). I will check the seat orifice and blow it out again.
Thanks

pete 23 · Nov 21, 2010

Adjusting the double float on that carb can add up to several different bends in the correct places. You want a minimum of clearance on the pin but it has to be perfectly free. No excess side clearance between float and hanger and then you have to get both sides of float equal height and breath. I did a ton of those carb over the years as the float is same from M up to 856 gas. I became so frustrated that I took an old carburetor and cut the bottom off for a gauge. This , when temporarily mounted to upper half will confirm if you have clearance on all sides of the float to lift and drop. I have also soldered a few leakers. What I find most of the time is people don't pay enough attention to the pivot area for loosness and getting the correct spread on the dual floats. The needle valve is another story all by itself. I find the seats are oblong in most and therefore coin them with an old inj nozzle pintle that has same angle as needle. Of course, even with all that, just a speck of crud coming down the fuel line can get under that needle and cause it to leak. Just some food for thought.

Hendrik · Nov 22, 2010

... and sometimes the leak is between the seat and the carb body.
You may use method in the link shown to trace your carb problem.
HTH, Hendrik
Float level and carb checking

Dan in Ore · Nov 22, 2010

Are you certain that the float is fixed? Even a small amount of gas in the float can make it sink.

I learned long ago to not try and repair a float if at all possible. It also may be that the weight of the solder that you put on the float is causing it to sink.

If it ran good when you first put it together, and later started flooding, I would replace the float.

Just my $0.02.

soybeanjoe · Nov 22, 2010

Even though you put a new needle valve & seat in it could still be the problem. I've replcade them & have had them stick within a very shrt time, like the first time I shu the tracr off.

Dave H (MI) · Nov 22, 2010

I'll tell you something and do what you will. If the float has no fluid in it when you pull it out and emits no bubbles when immersed in hot water then the seat is your likely candidate. If you replaced a solid needle with one of the neoprene tipped ones try putting the old one back in and see if it stops leaking. Once you get it to stop leaking there are cheap gravity flow filters that you can use along with a rubber gas line to check to see if a lot of crud is getting in the system from somewhere. Run it that way for a month or so and then put your regular line back on if it is running good and the filter does not block up. You can't just kit out a carb on what is basically an industrial machine that spent decades in the dirtiest outdoor environment imaginable. You have to work from the tank down and clean it all.

M carb float issues

Dick Binfield

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Dave H (MI)

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Dick Binfield

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pete 23

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Hendrik

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Dan in Ore

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soybeanjoe

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Dave H (MI)

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