My Tractor Forum banner

1 - 18 of 18 Posts

·
Morning Dew
Joined
·
22 Posts
Discussion Starter #1
Hello all-
I have a LawnBoy C-72 on a Model 1116 Hobby Gardener, circa 1961 or so. 16:1 mix.
Fully cleaned out the fuel tank and installed a new gas shutoff and fuel line, took off the carb , removed all accessible parts, and cleaned in an ultrasonic cleaner. Put it all back together and got it going, but it smokes something fierce and spews oil out the exhaust. It also died after about 30 minutes. I had to keep choking it to keep it from dying, then it crapped out all together. I'm wondering if the old cork float is sloughing off and clogging my main jet. That float is no longer manufactured.
Any suggestions on the smoke/oil issue, or the fact that it dies after a bit?

Much thanks
MorningDew
 

·
Premium Member
Joined
·
1,634 Posts

Attachments

·
4K Poster!!!!
Joined
·
4,783 Posts
The fact that you are having to choke it to keep it running would indicate a lack of fuel. I think you are probably right on track to suspect the old float is faulty. Just about every 1960s lawn boy that I have ever messed with needed a new float due to the shellac coating turning to what looks like carbon and falling off causing blockage and a sinking float.

Here is a link to one on ebay.
https://www.ebay.com/itm/GENUINE-OEM-LAWN-BOY-TORO-PART-95-1899-CARBURETOR-FLOAT-WILL-REPLACE-678113/281789965457?hash=item419bfda491:g:9CYAAOSwfglZwrw0
 

·
4K Poster!!!!
Joined
·
4,783 Posts
Here is a pic of my latest 1960s float. It was in a late 60s edger with a D-400 engine. The engine was pristine in every way, probably less than a couple of hours of use, but the float was terrible. The engine would only run on primed fuel, I took the carb bowl off and noticed the black chunks in the bottom of the bowl and figured quickly that the main jet was clogged. Cleaned the carb, and installed a new float and she now runs like a top.

The fact that yours is smoking a lot kinda goes against the theory that it's starving itself of fuel though. I'm kinda hoping that your excess smoke is just normal for a 16 to 1 machine (with choke on) and maybe the float sinking is causing a momentary rich condition until the chunks find their way into the jet opening.
 

Attachments

·
Morning Dew
Joined
·
22 Posts
Discussion Starter #7
Thanks lawn boy. Mine looked pretty similar. Epoxy in some areas, some not, and kinda black.
Hope the new float does the trick!
 

·
Registered
Joined
·
1,661 Posts
What oil are you using? That engine was built when all we had was non detergent motor oil, technology has vastly improved. If you are using a modern two stroke mix at 16:1 it will smoke and puke.
 

·
Morning Dew
Joined
·
22 Posts
Discussion Starter #9
Hi Roy-
Yes I am using a modern Stihl 2-stroke oil (the one in the gray bottle, their newer formulation).
The instructions that came with it said to use "high grade canned oil of SAE 30 body, Service MM, or outboard motor oil".
Should I just use some sae 30 motor oil instead?
 

·
Premium Member
Joined
·
1,634 Posts
What oil are you using? That engine was built when all we had was non detergent motor oil, technology has vastly improved. If you are using a modern two stroke mix at 16:1 it will smoke and puke.
This statement seems to be self contradictory. It indicates that old non detergent motor oil would burn cleaner than the vastly improved modern two cycle oil, when in fact the vastly improved modern two cycle oil burns vastly cleaner than non detergent motor oil.
 

·
Premium Member
Joined
·
1,634 Posts
Morning Dew, I hope I didn't come off as being rude to Roy, as that wasn't my intention.
But I have seen this conversation a hundred times, and know exactly where it leads. The next advice that will be given to you is to lean your mix ratios. And twenty guys will jump in with testimonial of how they have ran Opti whatever in their 2000 modle two cycle engines for the last 17 years at 50:1 with no issue. And I have no doubt what so ever that they are being truthful. However your C72 is not a modern needle bearing engine and simply requires more oil to lubricate the bushings.
Yes, modern day two cycle oil will still smoke at 16:1, but if you are puking oil out of the muffler, I suspect it has nothing to do with your oil mix, or ratio.
Lee
 

·
4K Poster!!!!
Joined
·
4,783 Posts
@MorningDew- I think the Stihl oil is fine mixed at the engine recommended ratio. Here is a video of my 1968ish Lawnboy edger using 16 to 1 Lawnboy fuel/oil mix. In my opinion a correctly running 2 cycle lawn boy will have about the same amount of smoke whether it's using 32 to 1, or 16 to 1. I'm like Lee, I prefer to use what the engine maker recommends for a ratio. Those Plain bearing wrist pins (effective to all stock Lawnboy engines prior to 1970) need a good supply of oil and as far as I know the Lawnboy engineers, now Toro, have never changed their recommendations on ratios for those prior to 1970.

 

·
Morning Dew
Joined
·
22 Posts
Discussion Starter #13
Thanks Unclee
I was hopeful that sae 30 would solve my problem! But you make sense, that modern oils should be cleaner.
However the cloud of smoke and the oil coming out of the exhaust just doesn't seem right.
If anything else occurs to you, please let me know.
 

·
Morning Dew
Joined
·
22 Posts
Discussion Starter #14
Hey 77 that's one nice machine! (not to mention the yard!!). My old LB definitely puts out much more smoke. Do you get oil from the exhaust? When I was working on it, I had it up on a low bench to make it easier to work on and it made a mess of the bench. We'll see whether the new float will help regulate the mixture.
 

·
4K Poster!!!!
Joined
·
4,783 Posts
Thanks Unclee
I was hopeful that sae 30 would solve my problem! But you make sense, that modern oils should be cleaner.
However the cloud of smoke and the oil coming out of the exhaust just doesn't seem right.
If anything else occurs to you, please let me know.
I'm optimistic that once you get the carb cleaned and tweaked with a good float installed your problems will be solved. I suspect what you are seeing right now is just residual oil leftover from short cold starts (choked), and possibly extra oil that a previous owner poured in the cylinder for storage. Once dialed in and warmed up it should all get clear. I would check the exhaust ports while you are at it though and make sure they are clear. With clear ports, a good functional carb and sealed crankcase that C engine should be good for a spring workout next year.
 

·
Premium Member
Joined
·
1,634 Posts
Thanks Unclee
I was hopeful that sae 30 would solve my problem! But you make sense, that modern oils should be cleaner.
However the cloud of smoke and the oil coming out of the exhaust just doesn't seem right.
If anything else occurs to you, please let me know.
I would probably replace the needle and seat along with the float, and make sure your gas shut off valve isn't leaking.
I suspect you have multiple carb problems. You are leaking fuel into the engine while it is at rest, and you have a jet restricted while running due to a deteriorating float.
Also I have no idea how long this machine sat without running, but I have seen old engines being started for the first time in many years smoke like a train until the rings free up and seat.
 

·
4K Poster!!!!
Joined
·
4,783 Posts
Hey 77 that's one nice machine! (not to mention the yard!!). My old LB definitely puts out much more smoke. Do you get oil from the exhaust? When I was working on it, I had it up on a low bench to make it easier to work on and it made a mess of the bench. We'll see whether the new float will help regulate the mixture.
Thanks for the kind words regarding the edger and yard, and to answer the question about the exhaust, yes it's normal to get some oil coming out of the exhaust on these old 2 strokes. I have a couple of mowers that I only crank up once a year or so, they don't cut grass, and after 15 mins of run time the decks underneath have a film oil around the perimeter that have to be wiped off. It's perfectly normal, one of those is a 1977 Bricktop NOS engine. In my opinion that spray of oil is a good thing, it keeps fresh oil throughout the engine. On the downside it does create build up in the exhaust and ports that have to be addressed from time to time.

I cringe every time I see that video and see my little bushes uncut. I can now report that those little bushes are now a pretty good ball shape. I may redo that video come spring when those rose bushes are in bloom and now that the bushes are a nice shape. Not to mention that I now have a good blue belt that works great on that edger. LOL

Edit: it's 92 degrees today! I think my lawn thinks it's an early spring. We might be the hot spot in the country today.
 

·
Premium Member
Joined
·
1,468 Posts
After reading the replies to your post, I agree with Unclelee that you have more than one problem. If you had to keep priming the engine to keep it running, you were not getting enough fuel. This could be restricted jet or needle adjusted to loo. Did you have the brass jet out while cleaning the carb ? Second, if you were getting oil and excessive smoke this could be from build up in the muffler and or excessive priming trying to keep it running. All said, you could also have other things contributing to poor running such as point setting wrong or spark plug gap wrong. I think new float and float valve are the place to start. Leaky gaskets, wrong point setting, spark plug set wrong or shorting out as well as bad oil seals could contribute to the problem. But start with the carburetor.
 
1 - 18 of 18 Posts
Top