Case 300 carb blues

[kenbob]

My marvel carb on my 311 is a real marvel. I can not get the carb set right. I have been working on it for 3 hrs trying to get the carb either to not run over when shut off or starve when run wide open. I thought the old float might have a hole in it. New float, set 1/4" gas running like a river. Been putting on, taking it off, about 30 times and cannot find a sweet spot or anything else wrong. I know I have plenty of gas going in all I have to do is drop the bowl to see that. When it dies the bowl is almost dry. Just for grins, how much gas should be in the bowl with everything working right. How far from the top? Thanks all. Ps I rebuilt carb,it has new needle and seat.

 

[kenbob]

After 2 more hrs of work I reached a compromise. I got it not to run over, and it only stalls out above 2200 rpm. I suppose the next thing to do is see how much gas actually free flows out of the carb bottom. One weird thing I noticed and cannot get my head around it. When it was running out the intake, and I took the long needle out so I could remove the bottom bowl, the flow would lessen. Put it back in and it would increase, take it out and it would lessen. I don't see how that has anything to do with a float set to high.

 

[RJKeith]

Just for grins, when you had it apart did you spray carb cleaner into the jets and see that it came out where it was supposed to?

 

[kenbob]

YEs, everything was sprayed and I even used those tiny brushes for cleaning carbs.

 

[Tgrasher]

Carburetors can be fickle, one would think since they are mechanical, that they could be set and all is fine. But other factors, dirt, water, temperature always seem to be able to change the perfect setting. I've given up trying to find perfect and have settled for a happy medium.

 

[used red MN]

YEs, everything was sprayed and I even used those tiny brushes for cleaning carbs.

And gave a blast of compressed air to aid in clearing out anything that may have dislodged by the probing? Had to ask, it needs to be done in my opinion. Also in my opinion and probably that of the design engineer of the carb adjusting the float to get more or less gas in the fue/air mix is a fallacy. If the main jet and idle adjustment screws don’t adjust the mixtures properly there is still a problem in the carb circuits or some other factor is causing your problem. Set the float level with the carb top gasket surface. If it is a real problem child I might check the actual spec and set it to that. If you shut it off and leave the gas on and the carb is still dripping an hour later your needle and seat is not sealing properly.

 

[mEl]

I would check the float to make sure it is not bent and rubbing the inside of the bowl, those carbs are just not that fussy, I use them exclusively! Look at the floats front to rear and make sure the floats are perfectly vertical, no tipping either way. I have never done it but have been told that the fuel level should match the cast line making up the logo on the side. if you want to check it that way, take the drain plug out and put a 1/8 barb fitting in there and put an open piece of plastic tubing on it, hold the tube above the carb top and turn the fuel on and the line of fuel in the bowl should match the horizontal cast mark on the bowl. I am assuming there is the name cast into the bowl.

 

[kenbob]

Thanks all. I am not sure the needle in the kit was correct. With the carb upside down float in as it came out of the box it wasn't even close to 1/4" or was it straight! Definitely at an angle. I will take it off again and take apart again to see what is going on with the needle. The old float did have some scratches on the inside where it may have been rubbing on the bowl.

 

[kenbob]

Running good for now! Did fuel flow check..Problem was in the carb. Took it apart cleaned everything and looked again at the old float. It had scratch marks on the inside. I think the trouble all along was it was scraping against the bowl and not rising when it should. All my adjusting only messed it up. Bent the float out just a bit. Put it together, shook it--heard it flopping inside. Put back on and seems ok. I take it for a Sunday Drive tomorrow to see.

 

[rustred]

One crazy thing I run into lately was the float drop. Kinda had the same problem turn on the gas and it would come spilling into the intake. Pulled the bottom of a few times and checked the needle and seat. Held it closed with the gas turned on and not a leak. So finally I thought wth that float sure looks low. So I set it to open the needle and stop there. From what I found it was sitting on the carb bottom instead of hanging inside. So it must have been too low to float . Put it together and opened the gas and no more leaking. It was a wierd one. So I think it was just too low and would not float to shut the fuel off. I do know there is always a float drop measurement in the kits or used to be.

 

[mEl]

Another hint, when working with the Viton tipped needles, never apply more than the weight of the float on the Viton needle as the brass seat is sharp and can cut the Viton with a lot of pressure. I have done many carbs in my career and have saved old needle and seat assemblies. Right or wrong, I take an old steel needle and put it in the brass seat and tap it very lightly just to maybe clean any rough or sharp spots if present, that just me, not necessarily recommending it but I have done many and build carbs for pullers and I do not like leakers. Glad you found the bent float, that is the most obvious cause of erratic leakage and one overlooked by many who do not do this all the time. Sadly, experience teaches and not all have been in the business. I have been told that experience is the best teacher, unfortunately, I have found it the most expensive also.

 

[chris142]

Make sure to put a good inline fuel filter before the carb.

 

[kenbob]

Thanks all

 

[kenbob]

Took the 300 on 40 mile tractor ride. During lunch I was talking to an Oliver guy who had all kinds of trouble with his tractor. I did not tell him my tle until after he was through. We both had the same problem. Float riding too tight on the inside of the bowl, Spreading the float out away from the bowl cured his problem just as it did mine. Very strange to have the same story twice in one week.