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A friend of mine is bringing me a mower to look at and says it will run for about 5 to 10 seconds and then shuts off. He told me it is a cub cadet but is a 2 stroke lawn boy. He looked it up and said it was a 1971 mower. I'm guessing it could be the carburetor or spark. I have never worked on a mower with points.
Does anyone know what the gap setting is for the points? I looked on the toro website and it looks like it could be a C or a D series motor from the time period. On the parts drawing pages it looks like part 677254 fits on some C and D engines. I guess I will start by cleaning the carb, checking for spark, and for compression. Then pulling the flywheel off to check the points and the crank seals and the exhaust ports. If anyone has any other hints or ideas, please send them my way.
Thank you.
Jerry

Mine is a later model but did the same thing. On mine the float needle seat is a rubber type ring down in the gas inlet, didn't like today's gas and expanded to the point that the needle valve was shut off. Replaced the needle and seat and it runs fine. Also on mine there is an adjustment screw that controls the air inlet to the carb. bowl, called the altitude adjustment. If closed down too much it will also cause the motor to shut down. Again, mine is a newer F engine that might be different.

You have spark...
It just may be intermittent.

viperv10 said:

A friend of mine is bringing me a mower to look at and says it will run for about 5 to 10 seconds and then shuts off. He told me it is a cub cadet but is a 2 stroke lawn boy. He looked it up and said it was a 1971 mower. I'm guessing it could be the carburetor or spark. I have never worked on a mower with points.
Does anyone know what the gap setting is for the points? I looked on the toro website and it looks like it could be a C or a D series motor from the time period. On the parts drawing pages it looks like part 677254 fits on some C and D engines. I guess I will start by cleaning the carb, checking for spark, and for compression. Then pulling the flywheel off to check the points and the crank seals and the exhaust ports. If anyone has any other hints or ideas, please send them my way.
Thank you.
Jerry

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Gap setting for points is .020 ---Dan

Thank you for your replies. My internet is just now up and running again. There was a nation wide outage on Century Link. I have some experience on F motors but almost none on engines with points. When I was young I had a dwell tach and a timing light and would make some money tuning up people's cars. Electronic ignition put me out of business. But it is a lot better system. If I run into any more problems I'll give you guys another shout.
Thanks,
Jerry

If indeed it's a 1971 Lawnboy IH (Cub Cadet) model it would most likely have a D-400 engine. If you need to order parts just for the engine just use any D-400 LB model from the early 70s to get access to the part catalogue, that is if there isn't a parts catalog available on the Cub Cadet site. A good LB model number that comes to mind is the 7260, (A, B or C). From memory I think there were only 2 versions of the IH Lawnboys back in the 70s and the electronic ignition (D-600) version didn't come out until 1972. If it's running on just primed fuel only, and then dying, more than likely it needs the carb cleaned, along with checking the usual suspects when dealing with a nearly 50 year old carb.

Edit; Just thought I'd throw this info out there if by chance you get real deep into this mower. The Lawnboy D-400 engine changed from 16 to 1 fuel/oil ratio to 32 to 1 in 1970, so not real sure what the IH was rated in 1972 because the shroud used on the D-400 IH models were actually late 60s vintage shrouds. If the engine is a late 60s version it would be slightly different as far as piston and rings and a few other details. If you find out that it's rated as a 16 to 1 fuel/oil mix model then you could bet the parts are going to match a late 60s LB, like for instance a 1966 model 5234. Please folks, I'm not trying to start a fuel/oil mix debate here, I'm just using what the factory rating stated on the mower to try and determine what internal parts might be inside the engine. FWIW the D-400 pre-1970 is my favorite engine and I think the Cub Cadets are the best looking of all the D-400s out there, but I've just never had the privilege of working on one, so I can't say if it's pre-1970 components, or not. In case anyone wonders why I personally like the pre 1970s better is because the engines were just better built with the crankshaft having dual bronze bushings and an extended snout crankcase that really help support the crank much better. After 1970 the only ones that had this feature were the commercial units.

Ok I will add to this one ..... If the muffler is stopped up like a LOT of the Lawn Boys do most of the time it can cause that issue also ....

My buddy Johnny says he remembers the points at 18 thou... 18 or 20 will work ........ 1200 grit sand paper works great for points....

Plus Tard Mon Ami ~!~!

Hi Jerry,

The D400 engine has a twin-spark ignition system (with points and condenser).

The D400 had an overly complicated (IMO) spark advance flyweight, with timing for starting at 6 degrees BTDC then once the engine catches advances the timing to 26 degrees BTDC.

Check the fiber wear block that rides against the cam on the crankshaft. Excessive wear can allow the breaker point arm to contact the crank and cause an electrical short circuit. I've learned from wrenching on cars a defective condenser can cause intermittent spark.

When adjusting point gap push the crankshaft toward the carb to eliminate possible bearing wear.

An 8255 L.B. has points for obtaining parts. The D600 was identical to the D400 except it had electronic ignition.

Regards

Jeff

Thanks again for more replies. I still don't have the mower yet, but my friend told me he thought it was a 1971. I don't know the model no. The mower came from a Lawn Boy repair shop from here in Bellefontaine that operated in the 70's and 80's. I remember driving by there but I don't think I ever stopped in there because I never had any trouble with my mower. It lasted at least 30 yrs. When I dig into this cub, I might have some more questions.Thanks again.
Jerry

Well I wanted to get back with you guys about that International mower. I got it the other day and found out that it was a D-600 engine with solid state ignition. It was nice out that day so I started it up outside my garage. It started right up but ran extremely slow, even when I turned the nob to high speed. It acted like the choke was on but it doesn't have a choke. So I let it run for a couple minutes and then shut the gas off to let it run the gas out of the line. When I turned the gas valve off the engine revved way too fast. I'm guessing way over 4000 rpm. So I shut it off real fast. I was thinking what in the world. Then I went into my garage to set up my work station ( a piece of plywood on tall saw horses). When I went back out to bring the mower in I noticed a solid stream of gas flowing from the carburetor and running over the deck and onto my yard. Will probably have a dead spot there in the Spring. Anyway I started by taking the carb off. It had the metal carb that you have to take the reed plate off. My old d-600 had the modular carburetor that 1 screw held it in place with an O-ring as a gasket. It didn't really look that dirty inside but the float was real dark and crusty looking. I gave it a good cleaning. I actually I gave the whole mower a good cleaning with Simple Green and some brushes. I took the engine off and replaced both top and bottom seals. I don't know if they where original or not but they where metal on the outside unlike the rubber or plastic ones today. The exhaust ports were clean but I got a least a cup full of carbon and crud from the muffler. When I first started the mower it smoked real bad. A lot of that was probably all the oil and crud int the muffler area. I scraped it real good and degreased it inside and out. I noticed when I was taking the flywheel off that the cd coil was in there cockeyed. The gap on one side was about 25 and 8 on the other. So i straightened them up and sanded them a little bit with fine sandpaper. The primer and fuel lines were hard as a rock so I replaced them. I broke off the plastic primer nipple on the carb so I had to add that to my parts order. It had a makes shift air filter so I replaced it also. Also the primer bulb was rotten so I replaced it too along with new carburetor and reed plate gaskets. Sharpened the blade and I thought I was ready to go. I set it down and primed it a couple of shots and it wouldn't start. After about ten or fifteen pulls I looked down a gas was dripping from the carb.
Back on my work bench it went. Gas was coming from the bowl gasket. It wasn't a good seal. That gasket looked good so I reused it. When I took the carb back off I noticed that the top of the reed plate gasket got folded over a little bit and it was probably sucking in air there. I had an extra bowl gasket there
for a V engine plastic carburetor so I used it and sealed it back up. When I turned on the gas back on gas started coming out through the gasket again. So I thought to myself again "what in the world". I thought that the plastic bowl must be warped or have a crack in it. So I robbed a carb bowl from another V
engine mower I have to see if that would work and it worked fine. I cleared some snow away from outside the garage and fired it up and let run for about five
minutes. OOh the sweet smell of success and two cycle exhaust. This a really neat looking mower. The shroud looks like a car hood scoop and is painted in cub cadet yellow and off white. I would post a picture or two of it but I wouldn't have clue how to do it. I'm not a bit tech savvy. Thanks for listening.
Jerry

I have been keeping my eye out there for one of those mowers. I have only seen one and it was in terrible condition and the owner wanted a premium for it. Good to hear that you got it going. Find someone who can help you get a photo uploaded so we can see it. I’ve got kids who tutored me on how to do those things.

My daughter helped me get these pictures uploaded.
I got it running good. I don't know how well it will run under a load. I had to take off the governor system off to change the top seal. I think I got it back on right but I'm not sure.
Jerry

Looks really good! Appears to have been well cared for, just used, but not abused. The Cub Cadet Lawnboys are one of my favorites. The color and graphics are just awesome. I'll bet you did just fine getting that governor assembled correctly. Just make sure that you didn't get the throttle over centered (rotated fully clockwise 12 to 1 oclock position) in getting it back together. When facing the lever it should be oriented to the 10 o'clock position, and it should have spring tension to push it back to that spot if manually moved. If over centered the speed can get out of control real quick. It will start at 10 o'clock and once it comes up to speed it should move down to the 8 o'clock pos, and when a load is applied it could be anywhere in between 8 and 10 depending on the amount of the load.

Viperv, that mower is in pretty good shape. Looks nice! I would love to find one of those in that condition. I’m sure you will get it sorted out and cleaned up. Thanks for getting the photos up. They gave me something nice to look at while I’m cooped up during a blizzard. Hoping we get an early spring.

Hey 2smoked, I see that you have a R7070. I also have a 1980 model. It was in pretty rough shape when I got it. The pull rope kept flying back out of my hand when trying to start it. I found that the flywheel key was partially sheared and bent. I honed it out and put new rings in it and cleaned everything out and it is probably the smoothest running lawn boy I have. Its my favorite trim mower. Most of the decals are worn off and it only has 3 yellow wheels but she runs like a new one. Not bad for being almost 40 years old. Take care.
Jerry

viperv10 said:

Hey 2smoked, I see that you have a R7070. I also have a 1980 model. It was in pretty rough shape when I got it. The pull rope kept flying back out of my hand when trying to start it. I found that the flywheel key was partially sheared and bent. I honed it out and put new rings in it and cleaned everything out and it is probably the smoothest running lawn boy I have. Its my favorite trim mower. Most of the decals are worn off and it only has 3 yellow wheels but she runs like a new one. Not bad for being almost 40 years old. Take care.
Jerry

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It’s interesting that you mention the smoothness of your R7070. Mine is also the smoothest in my collection which makes it a pleasure to use. I am also a fan of its early F engine. Very durable too. Mine also has 3 original yellow wheels, but I carefully painted the one that was white and the color match isn’t too shabby. Last year I found a free one that was of the self-propelled variation. The engine was toast but I now I have some yellow and black parts including the yellow wheels. Never was a fan of any of Lawn Boy’s self-propelled models anyway.