# Diagnostic Help Needed - Cub Cadet Self Prop. Mower SR621 w/ B&S 6.75 hp OHV Engine



## mun1son (Jun 6, 2010)

*Diagnostic Help Needed - Cub Cadet Self Prop. Mower SR621 w/ B&S 6.75 hp OHV Engine*

Hello all. Brand new here and a novice small engine DIY'er, but good at comprehending and following instructions.

Lawn Mower background:

I've owned this mower for 6 or 7 years with no problems until the start of mowing season last year. I had trouble getting it to stay running. I could get it to start by putting gas or carb cleaner directly into carburetor. It would run for 30 seconds or so and then die. I did not feel like messing with it, so I parked it on the side of my house - bought a cheap used replacement mower - and the Cub Cadet had been sitting idle ever since. 

A few weeks ago, a friend was in need of a cheap mower, so I gave him the cheap used replacement mower I purchased last year and decided I would endeavor to try and get my Cub Cadet up and running again.

I've done some online research, reading, and watched a couple of videos on lawn mower repair.

Here is what I've done and/or attempted to do so far:

- Removed and reinstalled the carburetor and attempted cleaning it with carb cleaner. I used a wire to poke through the holes/jets on the carburetor and the screw that attaches through the bottom cup of the carburetor.

- Removed and replaced torn primer bulb.

- Replaced air filter. 

- Cleaned out gas tank and lines

- Replaced Spark Plug

- Checked for spark (there is spark)

When I filled the gas tank, gas started pouring out the little breather hole in the primer bulb. I don't remember the old primer bulb having a breather hole. 

With the spark plug installed, the starter rope will not budge. When I remove the spark plug, the starter rope easily pulls.

The blade will manually turn - its not locked up. The engine has oil.

Any ideas?


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## geogrubb (Jul 28, 2006)

First, welcome to the forum;
Please post the engine model, type and code numbers for the engine so we know what you have, sounds like a varnished carb and will probably need cleaned and a kit installed. Have a good one. Geo


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## 30yearTech (Sep 14, 2006)

Gas leaking out the vent hole in the primer means your carburetor is flooding. There is likely liquid in the cylinder and this may be why you cannot pull the rope with the spark plug installed. As Geo suggested you probably need to clean out the carburetor and install a kit, or at the very least a new float needle and seat.


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## mun1son (Jun 6, 2010)

Here is the code I see on the engine:

122602 0103E1 020406 FB

Is that the number needed?


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## 30yearTech (Sep 14, 2006)

mun1son said:


> Is that the number needed?


Yes, that's all the numbers needed from your engine.


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## mun1son (Jun 6, 2010)

30yearTech said:


> Yes, that's all the numbers needed from your engine.


OK great! I also found this number if it's of any help:

12A-979I100/700

I was reading the other thread about the guy who fixed the two throw away mowers. The cost is the thing. That's why I'm trying to figure out how to do this myself. By the time I pay someone to repair it, I could have just bought a good used one off of craigslist. You cannot get much more than $25 to trade it in, and I just cannot see giving my old mower away for that cheap, when I'm sure it has to be an easy fix. Then they turn around and sell it for $150 to $200. 

I've got my fingers crossed that you guys can guide me in the right direction.

I did clean the carburetor already, but may not have done it good enough. I did notice that the little float thing was filled with liquid, but could not figure out how to empty it. Is it supposed to be filled with fluid? Does a carb kit just include new gaskets?


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## 30yearTech (Sep 14, 2006)

Well this is what I do for a living, but I can't fault anyone for doing it their self. I am certainly glad that not everyone fixes their own equipment.

The float should not have any liquid in it. It cannot be fixed, the float must be replaced. They are not very expensive and not hard to replace. 398187 float is the part you need, they run about $7.00.


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## mun1son (Jun 6, 2010)

30yearTech said:


> Well this is what I do for a living, but I can't fault anyone for doing it their self. I am certainly glad that not everyone fixes their own equipment.
> 
> The float should not have any liquid in it. It cannot be fixed, the float must be replaced. They are not very expensive and not hard to replace. 398187 float is the part you need, they run about $7.00.


Thank you very much! I'll replace the float and post back.

I'm sure you don't have to worry about everyone fixing their own -  - and I'm thankful that you share your knowledge here with those of us who attempt to do it ourselves. You are appreciated.


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## mun1son (Jun 6, 2010)

The float worked! The mower works! Thank you very much!


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## [email protected] (Jun 17, 2013)

*gas comes out exhaust*

I have a 3.5 Tecumseh legend engine that gas comes out the exhaust when trying to start. do any of you have any idea what is causing this. I have changed the oil and gas is not getting in the oil. I would sure appreciate some help.:wave:


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## Don L (Jul 14, 2012)

mun1son said:


> Thank you very much! I'll replace the float and post back.
> 
> I'm sure you don't have to worry about everyone fixing their own -  - and I'm thankful that you share your knowledge here with those of us who attempt to do it ourselves. You are appreciated.


We have customers who own auto repair shops who bring their small engines to us for repairs.I do'nt think you have anything to worry about either.
I have learned from you too.Thanks,Don


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## Rentahusband (Aug 25, 2008)

[email protected] said:


> I have a 3.5 Tecumseh legend engine that gas comes out the exhaust when trying to start. do any of you have any idea what is causing this. I have changed the oil and gas is not getting in the oil. I would sure appreciate some help.:wave:[/QUOTE
> 
> Sounds like the carburator is flooding the engine. The needle/seat and float control the fuel flow into the engine. If either of these parts are not working properly, the engine will flood with fuel. If you search You Tube for Tecumseh carburator repair, it will show you how to repair it.


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