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Lifetime Lawn Guy
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Discussion Starter #1 (Edited)
Just got this and have been messing with it all morning trying to get it running right. (rain day here). Have replaced the governor rod as it was pretty worn, thinking maybe it was letting in too much air. Replaced the float, needle and seat, checked to be 100% sure the float was set to spec. 15/32", new gaskets all around... The carb appears to have been totally rebuilt already, the needle and seat appeared brand new, as well as the float, reeds, etc. But when I put fuel in it it fired in one pull, but this is ALL it will do. Nothing I did to it changed anything. As you can see in the video, I turned the fuel OFF and as soon as it runs out of fuel it takes off and runs right for about 2 seconds before dying.

Video:

I'm really scratching my head on this one. Got it from es_bob and he said it was running when it was put in storage a few years ago. I did nothing to it after unpacking it and putting it together other than putting some mix in the tank, priming a few times, and pulling the cord.
 

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Stupid question, you didn't clean the float with carb cleaner? I learned that one the hard way. You might want to drop it in some gas and see if it still floats. Are the fuel lines tight? Check the new gaskets, I've had them leak, went back to the old ratty looking gasket and it sealed right up. Plug look good? Exhaust ports clean?
 

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My guess is you have a faulty primer and it is providing another path for fuel to get to the venturi. Notice that the primer is the original factory installed where the rubber flapper is installed and the end of the plunger is peened to secure it, now it is possible that someone had some factory primers and peened a new one on it, but I doubt it.
 

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Lawn-Boy fan
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I never thought of it being a faulty primer, does that happen on these old Ds? Jason I could send you a different carburetor that is known good. Does it leak fuel if you shut the mower off and leave the tank shut off turned on?
 

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I never thought of it being a faulty primer, does that happen on these old Ds? Jason I could send you a different carburetor that is known good. Does it leak fuel if you shut the mower off and leave the tank shut off turned on?
Yes that is a common problem on these D400's as they age and that rubber flapper wears out. It's a real easy fix to put a new one on and they are usually available via ebay for 10 bucks or so.
 

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Lawn Boys Never Die
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Have you tried adjusting the knob on top the carb?? I had an 8229a at one time that was very sensitive. I spent along time getting it dialed in correctly.
 

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Lifetime Lawn Guy
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Discussion Starter #9
Thanks guys, well I ended up pulling the reed plate off again and went ahead and replaced the reeds. They looked new, but after replacing them I reassembled (again) and it fired right up! The only other thing I did was pulled the shroud off and regapped the coil which was set wider than .010

Didn't use any carb cleaner of any sort, it was CLEAN inside and looked to be a new float, needle and seat. I swapped the needle valve with another new one and replaced the float with another newer one I had and double-checked the float setting while I had it off.

Don't know if either the reeds or the coil adjustment could have caused the issue, but it seems to be fixed now. I want to check/adjust the RPM's now before putting the shroud back on so I've only ran it for under a minute, but I was able to shut it off and restart it in one pull so I *assume* it will be ok now.

Yeah, I should have replaced the primer as well... It didn't look bad at all though, it's working fine, but that's right about it letting air in if it's not sealing right. I think I have a few, but don't recall seeing any in digging for parts, but I wasn't looking for one either.

No fuel leaking out of the carb after it sat for 15 minutes or so either.
 

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Lifetime Lawn Guy
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Discussion Starter #10
Have you tried adjusting the knob on top the carb?? I had an 8229a at one time that was very sensitive. I spent along time getting it dialed in correctly.
Oh yes, I could close it completely or open it up to 2 turns with no changes at all... Spec is 1 turn out then fine tune from there. I'm sure I'll have to lean it down a bit once I put the air filter back on too. At least you don't need a long 1/4" wrench to adjust them!
 

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Glad you got her running good! Nah when the primer flapper is not acting as a check valve it lets fuel come up through the primer circuit, not air, basically turns the carb into a 2 barrel carb. LOL the flapper may have just seated properly around the plunger end, whereas when you initially started and the circuit was dry the little flapper got stuck up on the dry wall and allowed the fuel to enter venturi, just a hunch...glad you are good to go with that original primer, it is rare to have a 1972 D series with an original plunger installed, good deal!! I got lucky and Baldguy was nice enough to give me some factory primer assemblies and he also taught me how to do the factory peening so all my D series are equipped with the factory ones to.
 

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Lifetime Lawn Guy
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Discussion Starter #12
My guess is you have a faulty primer and it is providing another path for fuel to get to the venturi. Notice that the primer is the original factory installed where the rubber flapper is installed and the end of the plunger is peened to secure it, now it is possible that someone had some factory primers and peened a new one on it, but I doubt it.
Well, after messing with it some more tonight it went right back to running the way it was! I had a new primer assembly so I pulled the carb off AGAIN and replaced it and now it runs perfect! I'm betting that since it sat in storage, dry, for a few years the little rubber plunger on the end just got to where it wouldn't seal 100% anymore. UGH how I wish I had known to replace that FIRST before I spent half a day dinking with it replacing stuff that wasn't wrong! :duh: Granted the governor shaft was worn, so replacing that wasn't a bad thing, but everything else I did other than replacing the primer just now was a waste of time!

This is the same way the pile of junk I bought, and was able to return, from OMCjunkyard was running when I got it as well. Same engine... It had a plethora of other issues though.

Well, now I know. If a D series runs like that, replace the primer first!
 

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Lawn-Boy fan
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I never knew that about the primers on the Ds like that either. Good to know for future reference and good to have people like Lawnboy77 on this forum.

Jason I sent you another message on eBay.
 

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Thanks guys, glad to be able to help. Yeah on the D400's if it runs excessively rich like Jason's was with the main nozzle adjust knob fully CW (closed) then it's almost guaranteed to be getting the fuel through the primer circuit.
 
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