New Carburetor - Cub Lo Boy 185 -still won't start

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sanderson34
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New Carburetor - Cub Lo Boy 185 -still won't start

Postby sanderson34 » Mon May 20, 2019 7:13 pm

Hello everyone.

I've had a Cub Lo Boy 185 for about 5 years now. The Lo Boy would start right up with the slightest pop of the ignition. Idled correctly and the throttle allowed it to rev up. The last time I had this machine running "decent", it was stalling after running the mower for about 10 minutes. 3 years ago I cleaned and rebuilt the carburetor using a rebuild kit from Hamilton Bob's. After that, I was never able to get it to start on it's own again. If I gave it a shot of starting fluid, it would run very briefly and hard, so I knew I had messed the carburetor up. Fast forward 3 years...

Once again -a shot of starting fluid would run the engine briefly and hard. After trying to clean the carburetor again and inspect, I was unable to get it started. I removed all gas from the tank, removed and cleaned the fuel strainer bowl and have ensured that the carb is getting adequate fuel supply. I must have messed up the rebuild. So I bought an aftermarket carburetor.

This is the one I purchased -> https://www.reliableaftermarketparts.com/item/97057/70949c92-70949c92-new-zenith-carburetor-made-for

I installed it doing the governor lever to throttle plate, "wide open" recommendations, hooked up air hose and fuel line. Still will not start. However, when I crank the machine over...it will run very briefly, then sputters out. If I continue to crank the machine over, it acts like it's running, but will only run for 3 seconds after I move the key from the start to run position before sputtering out....The exhaust is constantly putting out smoke and exhaust...so it's cool to pretend it is running.

Also....there is fuel dripping from the cork looking spot directly under the carb towards the air hose intake.

Does anyone have anything I can try or additional steps to get this thing started?

:lost:

tst
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Re: New Carburetor - Cub Lo Boy 185 -still won't start

Postby tst » Mon May 20, 2019 7:34 pm

have you looked over your ignition system, points, cap etc?

sanderson34
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Re: New Carburetor - Cub Lo Boy 185 -still won't start

Postby sanderson34 » Mon May 20, 2019 7:37 pm

No. I have never looked at them. I assumed since it was running before I initially removed the carb, there was nothing wrong with those items. Could I be wrong?

tst
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Re: New Carburetor - Cub Lo Boy 185 -still won't start

Postby tst » Mon May 20, 2019 7:54 pm

sure, points are a wear item

sanderson34
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Re: New Carburetor - Cub Lo Boy 185 -still won't start

Postby sanderson34 » Mon May 20, 2019 8:13 pm

Which section of the manual/ service manual describes these procedures. I can't find it.

sanderson34
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Re: New Carburetor - Cub Lo Boy 185 -still won't start

Postby sanderson34 » Mon May 20, 2019 9:27 pm

Well....went back out to crank her over. Got her going with starting fluid...worked the choke....and bam! She's running. I guess I just needed to work the choke and crank her...got it going though. :{_}:

I drove around for about 20 mins and threw the mower blades on and she cut just a little bit. Engine RPM's eventually starting to go down and a belt in the PTO was squealing. Basically I am having the same mower issue as before. I would need to push the clutch in to allow the RPM's and the mower blades back up to speed. We'll see what happens but maybe I ought to wait for the daylight. :idea:

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Re: New Carburetor - Cub Lo Boy 185 -still won't start

Postby Don McCombs » Mon May 20, 2019 9:34 pm

Sounds like it's time for a tune-up and valve adjustment.
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sanderson34
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Re: New Carburetor - Cub Lo Boy 185 -still won't start

Postby sanderson34 » Mon May 20, 2019 9:55 pm

Oh my. I'm not sure I can accomplish those 2 tasks. I am looking over the engine service manual and it looks like removing and checking the valves is a bit involved....not sure I'm smart enough to figure it out.

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Re: New Carburetor - Cub Lo Boy 185 -still won't start

Postby Larry B » Mon May 20, 2019 10:21 pm

Spark, fuel, compression......secret formula

If it will fire and run for a while you can assume you have enough Compression. If you wanted you could pull the hood and get a compression tester and test each cylinder.

Have you checked your spark plugs? First thing to do is put a new set of plugs in it. If it is a light use tractor I would use Champion D21 plugs, for one used for mowing then D18Y plugs, if you plan to run it hard in hot weather then D16Y plugs. 025 gap. File and gap the points at .020 and see if the spark will jump a 1/4" gap. If it does it will run the tractor. Coil breaking down can cause it to run till hot then lose power. Are the plug wires brittle, cracking or crumbling? With the tractor idling spray some water on the plug wires. If tractor starts missing change cap rotor and wires.

Before you worry about valves make sure the ignition is working properly.

sanderson34
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Re: New Carburetor - Cub Lo Boy 185 -still won't start

Postby sanderson34 » Wed May 22, 2019 12:55 pm

Is there anywhere in the tech manual sections that discuss changing or checking points and ignition coil???

Also, the plug wires seem to be fine and I put new plugs in it when I purchased the machine, 5 years ago.

Thanks all

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Re: New Carburetor - Cub Lo Boy 185 -still won't start

Postby Larry B » Wed May 22, 2019 4:49 pm

Changing points is easier if distributor is out of tractor. Couple ways to do it. My way. Turn engine till it is at TDC with rotor pointing to #1 Plug wire. Remove distributor cap and mark side of distributor where rotor lines up with the distributor. Take center punch and make a punch mark near base of distributor and make a corresponding mark on the adapter distributor mounts in. The Marks are so you can get distributor back in exact same position. Remove the distributor hold down bolts and remove distributor. Change points being sure the contacts are flat and parallel to each other. Gap is .020" hold the drive gear and twist the rotor back and forth. Should feel it move a little then spring back. That is the centrifugal advance. Weights and springs are under the point plate. They can seize up. Might want to take point plate out and lube them. Remove your plugs and post a pick of the ends. Just curious. 5 years old. I would put a new set of plugs in.
Put the distributor back in lining up the rotor and the punch Marks. If you have an ohm meter you can measure across the 2 screw terminals of the coil. Should be right at 3 ohms. You should be able to get a good spark across a 1/4" gap. If it does it will run the tractor. Some guys remove the distributor and adapter so it can only go back in correctly or 180* out.

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Re: New Carburetor - Cub Lo Boy 185 -still won't start

Postby BigBill » Thu May 23, 2019 6:04 am

I take fine sandpaper to clean the points then turn the paper to the smooth rear side and clean the grit from the points. Regap and your good to go.
I'm technically misunderstood at times i guess its been this way my whole life so why should it change now.

Larry B
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Re: New Carburetor - Cub Lo Boy 185 -still won't start

Postby Larry B » Thu May 23, 2019 7:45 am

I guess I will show my age here. I still use the point file I got in a Sears tune up kit in 1973.

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Re: New Carburetor - Cub Lo Boy 185 -still won't start

Postby Jim Becker » Thu May 23, 2019 11:41 am

BigBill wrote:I take fine sandpaper to clean the points then turn the paper to the smooth rear side and clean the grit from the points. Regap and your good to go.

And then put in new points because you just ruined them.

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Re: New Carburetor - Cub Lo Boy 185 -still won't start

Postby BigBill » Thu May 23, 2019 8:32 pm

They used a point file years ago. The new points come coated and how do you get the coating off. It won’t run with the coating on them.
I'm technically misunderstood at times i guess its been this way my whole life so why should it change now.


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