1953 50 carb rebuild

bztguy

New User
I just rebuilt the carb on my dads 50. It had sat for about 5 years having never been ran with the old fuel left in it. It's pops right off and idles fine but won't run unless fully choked. If I even crack the choke open just a hair it dies. I don't believe I have an air leak around the gaskets. I soaked the carb in cleaner for 24 hours and washed out with carb cleaner. The passages are clear as I can blow cleaner through them. Any ideas?
 
I am not familiar with that particular carb, but it certainly sounds to me like something in your idle passageway system is not open or is not fully open/partially obstructed. If it will only run under a full choke you have a fuel restriction somewhere.
 
Unless you removed those pesky steel balls, your carb is still plugged with rust and crap Probably should send it to someone familiar with a Duplex carb for your 50.
 
I've worked on several of these and the main jets and the idle passages have to be thoroughly cleaned....seems like your work was mostly consmetic...
 
Ok, took it apart again and found one passage way blocked. Tractor now runs fine without choke on but starts to surge after driving for a couple of minutes. Like it's governor hunting then it usually dies. Upon re-starting I need full choke for the first 10 seconds or so then it's back to normal. I'm thinking I have a fuel delivery problem to the carb and it's running the bowl empty. I cleaned the screen and the sediment bowl and it seems like i have good flow into from the tank into but it's cloudy. It does have fresh gas but it sat for about 5 years with the old fuel in it which I did drain. Next step is drop the fuel bowl assembly from the tank and flush it and the fuel lines out. Any suggestions on the best way to flush the tank out?
 
(reply to post at 15:01:13 08/31/17)
BZ, I've had the same carb apart 3-4 times before I could get it right...take some bread ties...move the plastic and run up into the 3 idle ports or also use torch cleaners the small ones...or small wire...if you could get the balls out it is simple but those things are next to impossible...some grind them out and put plugs in their place...also remove the main and clean...I use the Berryman type cleaner...it's a job to get this stuff out....be careful not cross thread or mess up the compensator valve...
 
(reply to post at 16:15:13 08/31/17)
If you can get it to idle...I'd get about 2 cans of seafoam...make a hot mixture of about 5 gallons of gas and run it throught the carb....you might be able to cleaning it while running...if you get it to run through idle take it for a workout...will clean up....there is another product called mechanic in a bottle that will also work good...got to clear out the carb...
 
Does it have the automatic fuel shut off type bowl ? If so those have small passage ways to get junk stuck in them and you have to make sure the rubber washer on the center stem does not stick to the top when running,it has to go down with the stem.
 
Full choke to run at high idle is fuel starvation. Make sure your fuel supply is a good stream out of the bowl, float level too low, main fuel nozzle plugged, without using the correct drill bits theres no way you would be able to make sure those passages are clean. I have used the correct wire size for all the passages before, it works but not as good as drill bits. Every 2 cylinder that leaves my shop is placed on the dyno for a few hours and adjusted as perfect as possible. Hope this helps
 
It was as I suspected. It was s fuel starvation issue to the carb. I dropped the glass bowl assembly from underneath the tank and the inlet to the it from the tank was almost completely blocked. It's a miracle it ran at all. That explains why it ran perfectly for a minute or two upon driving then would die but would idle all day long just fine. It was running the carb bowl empty under higher RPMs as I had figured.
 
(quoted from post at 19:24:28 09/14/17) where are those pesky balls located.

Where the setscrews are in the photos below.

I machine the balls with a carbide end mill, then tap the holes for setscrews.

IMG_1934.JPG


IMG_1939.JPG
 

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