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Discussion Starter · #1 ·
Just thought I would throw this out there and see if any of you guys notice more exhaust smoke from your D-600's compared to the D-400's and the F engine'd models. My 1974 7263 smokes twice as much as my other 2 mowers and they all use the same 32:1 Lawn Boy oil mix. Most of you here know mower that I am talking about and saw the ground up resto. Everything is either new or reconditioned on this mower and every part in the carb is brand new. The float level is dead nuts too. I checked it like 3 times. Maybe it's because the fixed jetting is a little on the fat side??? I dont know. I would like to make this thing run cleaner but maybe that's just the way they are. Tell me what you guys know.

Ross



 

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Ross, I don't know if they are supposed to smoke.
Mine always smoke a little to start and then settle down.
That is still a beautiful job you did on that mower. :fing32:
 

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Not sure about smoking as my 5232 smokes like all 2 strokes at start. That mower looks smokin' though!
Nice job.

MU
 

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First off,I can barely see it in the picture (so I may be wrong) but it looks like the throttle arm/governor rod is in a straight up position. If it is, your governor needs to be adjusted. At rest the lever should be at a 45 degree angle. Although this is not making the smoke, it should be right before checking the high rpm (3200) and adjusting the carburetor needle.
 

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My D-600's that I had use to smoke less then my D-400's. I would say oil mixture , but you stated that all of your mowers use the same fuel mixture from the same can. Now I will throw this out. I have two F engines. One smokes normal compared to the rest of my mowers and the other one smokes normal for 5 min then stops and you can hardly see any smoke. Is your altitude adjustment screw adjusted correctly? Thats the only thing that I can come up with. How excessive is the smoking?
 

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I agree with Mike72's observation. My 7263 runs like all the others I have, although it hasn't been ran since last year.
 

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Discussion Starter · #8 ·
First off,I can barely see it in the picture (so I may be wrong) but it looks like the throttle arm/governor rod is in a straight up position. If it is, your governor needs to be adjusted. At rest the lever should be at a 45 degree angle. Although this is not making the smoke, it should be right before checking the high rpm (3200) and adjusting the carburetor needle.
Good eye Mike. The photos were taken right after final assembly and the governor has since been adjusted properly amongst other things. The mower doesn't smoke unbearably but just a lot more than my F and D-400. I have spent quite a bit of time trying to dial it in with the mixture screw but it seems to have little or no effect. As a matter of fact the mower runs its best with the screw turned 1/4 out from the seat. The fuel consumption seems to be higher on this mower and I know that's why it probably tends to smoke more. What would cause that? Over all the mower runs great but just sucks gas and smokes more. Maybe the carburetor body is shot??
 

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Is the sealing washer on the main jet in good condition? If you have a new main jet, was the hole the same size as the old one? If the float level is set and the float is not logged,I don't know what else it could be.
 

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If the carb body is used, other than new parts, you could still have a blockage somewhere. Maybe another good round of cleaning and compressed air?.
 

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I just remembered something about this carburetor. There was a new main jet that superceded the old one. The part number for both is the same,(607568) but the newer one is longer and does not have the side hole. The length of the new jet overall is 1.536. The old one is .825 long overall. Of course you may already have the newer one.
 

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Discussion Starter · #12 ·
I just remembered something about this carburetor. There was a new main jet that superceded the old one. The part number for both is the same,(607568) but the newer one is longer and does not have the side hole. The length of the new jet overall is 1.536. The old one is .825 long overall. Of course you may already have the newer one.
Mike I know exactly what you are explaining here. When I went through the carb I decided to order all brand new parts for it. When I went to assemble it I did notice that the new main jet was indeed longer with no hole in the side as you describe. I thought it might be the incorrect jet since it hung lower into the float bowl so I didn't use it and decided to use the old one that originally came out of the carb since it was clean and un-damaged. Do you think that Lawn Boy redesigned the jet to correct the symptoms that I am experiencing? Maybe the absence of the side hole in the newer jet leaned the mixture just enough to cure the problem??? Let me know what you think.

Thanks Ross
 

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Ross, have you read the service bulletin on the jet change? I can scan and post it later today. It mentions hot start problems as the reason for the "fuel nozzle" change, but says nothing about fuel consumption, but I wonder. Interestingly the bulletin is dated 1972 and your mower was made in 1974.
 

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Assuming the carb mixture is correct, where the engine should be "four cycling" only a small percentage of the time, the muffler could be loaded with deposits that take time to burn out. Try to run it under a good load for a while, if this is the problem, the smoke will increase and its smell will change, then it should diminish. That is, by the way, a very nice looking mower you have there.
 

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Discussion Starter · #15 ·
Ross, have you read the service bulletin on the jet change? I can scan and post it later today. It mentions hot start problems as the reason for the "fuel nozzle" change, but says nothing about fuel consumption, but I wonder. Interestingly the bulletin is dated 1972 and your mower was made in 1974.
No I haven't seen the bulletin. Post it up so we can all see it. I do have the newer style jet so it won't hurt to try it and see what happens. Thanks for researching.

Ross
 

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Discussion Starter · #16 ·
Assuming the carb mixture is correct, where the engine should be "four cycling" only a small percentage of the time, the muffler could be loaded with deposits that take time to burn out. Try to run it under a good load for a while, if this is the problem, the smoke will increase and its smell will change, then it should diminish. That is, by the way, a very nice looking mower you have there.
The muffler is clean. I thoroughly cleaned it when I rebuilt the mower. When the mower gets good n hot the smoke subsides some but puffs out more than I think it should. Thanks for the compliments.
 

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Here is the service bulletin. It doesn't say anything about smoking, but it still might be the answer to your problem.
 
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