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5247 (1980) won't restart. Carb adjustment problems?

Apr 7, 2012#1

Gene123

I've been trying to get a 5247 (1980) running. It has an F100 engine with "the late model" carburetor. I resolved the problem of gas leaking from the foam filter --- thanks to help from some of the fellows on this forum (Fireman, Two Stroke, & others). Good guys :thumbsup: I installed a new needle & seat as they suggested, primed it twice, and it started like a champ. I mowed for about twenty minutes, turned it off, and it wouldn't restart. Questions: 1. Is the .010" clearance between the coil and the flywheel crucial? I may have gotten it off a little. 2. If I got the float level off 1/16", would that cause the problem? 3. After setting the governor to real low rpms, I screwed in the "adjustable fuel flow needle valve" until it started stalling (or "hunting"), then I backed off on the screw about half a turn until it smoothed out. Could that adjustment be causing it to not restart?

Apr 7, 2012#2

Fireman 123

Gene123 said:
I've been trying to get a 5247 (1980) running. It has an F100 engine with "the late model" carburetor. I resolved the problem of gas leaking from the foam filter --- thanks to help from some of the fellows on this forum (Fireman, Two Stroke, & others). Good guys :thumbsup: I installed a new needle & seat as they suggested, primed it twice, and it started like a champ. I mowed for about twenty minutes, turned it off, and it wouldn't restart. Questions: 1. Is the .010" clearance between the coil and the flywheel crucial? I may have gotten it off a little. 2. If I got the float level off 1/16", would that cause the problem? 3. After setting the governor to real low rpms, I screwed in the "adjustable fuel flow needle valve" until it started stalling (or "hunting"), then I backed off on the screw about half a turn until it smoothed out. Could that adjustment be causing it to not restart?

Glad you got part of the problem fixed. Sounds like you have got a typical old Lawn Boy on your hands. Good thing we love these little machines, and show them a little mercy haha. I haven't had the same issue, but I would check to see if the exhaust ports are clear of any carbon build up. If that's not it, I suggest tinkering with the carb until you get it lined out. As for clearances, I use a business card to set the gap on the flywheel, and the float I just set to to level with the carb body. This has worked for me so far. Good luck!

Apr 7, 2012#3

Gene123

Fireman 123 said:
Glad you got part of the problem fixed. Sounds like you have got a typical old Lawn Boy on your hands. Good thing we love these little machines, and show them a little mercy haha. I haven't had the same issue, but I would check to see if the exhaust ports are clear of any carbon build up. If that's not it, I suggest tinkering with the carb until you get it lined out. As for clearances, I use a business card to set the gap on the flywheel, and the float I just set to to level with the carb body. This has worked for me so far. Good luck!

I'll try all that tomorrow. Using a business card to set the gap on the flywheel --- what a good idea! I sure appreciate your help, Fireman.

Apr 7, 2012#4

D

dougw

Might check and make sure it is getting spark. I have had ignition modules quit before. Also exhaust ports plugging up will make it low on power and smoke a lot along with hard to start.
Doug

Apr 8, 2012#5

Gene123

dougw said:
Might check and make sure it is getting spark. I have had ignition modules quit before. Also exhaust ports plugging up will make it low on power and smoke a lot along with hard to start.
Doug

Good idea. I hadn't thought about the coil suddenly going out. Do they abruptly go out, or do they slowly fade away?

Apr 8, 2012#6

D

dougw

I have seen both many times they seem to lose power but work for a while before quitting other times they work one minute then quit the next. Might check and make sure the wire to the switch and the ground are good and gap is correct then check it with a meeter before deciding it is bad.

Apr 8, 2012#7

Gene123

dougw said:
I have seen both many times they seem to lose power but work for a while before quitting other times they work one minute then quit the next. Might check and make sure the wire to the switch and the ground are good and gap is correct then check it with a meeter before deciding it is bad.

I didn't know a coil could be checked with a meter. How is that done?

Apr 9, 2012#8

Two-Stroke

Gene123 said:
... 3. After setting the governor to real low rpms, I screwed in the "adjustable fuel flow needle valve" until it started stalling (or "hunting"), then I backed off on the screw about half a turn until it smoothed out. Could that adjustment be causing it to not restart?

I'm not sure why you adjusted the needle valve that way. Did you read that in a manual? I'm not saying it's wrong but I've never heard of doing it that way.

I adjust the needle valve by testing how the mower performs under load (cutting normal height grass) while fully warmed up.

To get it started, it may be necessary to reset the needle valve (try turning it all the way in -- then out one turn) -- fiddle with it if necessary.

Apr 9, 2012#9

H

hankthecrank

1 preset altitude needle 1/2 turn from seat
2 start and let warm for 3-5 min.
3 place speed control to low
4 slowly turn needle CCW until engine running smoothly
5 place control to high, if not running smoothly turn CCW 1/8 turns at time till smooth
6 shut-off and immediately try to restart, DO NOT PRIME, should start within a couple pulls at both
low and high settings, if not contitnue turning needle 1/8 turns CCW to obtain easy starting.

This is from manual, good luck, looks like everyone pretty much have it covered. Fuel+ Air+Combustion+Ignition=VROOOOOM.

Apr 9, 2012#10

Gene123

Two-Stroke said:
I'm not sure why you adjusted the needle valve that way. Did you read that in a manual? I'm not saying it's wrong but I've never heard of doing it that way.

I adjust the needle valve by testing how the mower performs under load (cutting normal height grass) while fully warmed up.

To get it started, it may be necessary to reset the needle valve (try turning it all the way in -- then out one turn) -- fiddle with it if necessary.

Thanks, Two Stroke. I'll try that as soon as it stops raining. I don't have a manual. I've just copied bits and pieces from the internet. I've been reading a lot --- got so much swimming around in my noggin it makes me dizzy. :laughing:

Apr 9, 2012#11

Fireman 123

Buy a mechanics handbook from eBay. It's very useful if you're planning on keeping the old mowers going.

Apr 9, 2012#12

Gene123

Fireman 123 said:
Buy a mechanics handbook from eBay. It's very useful if you're planning on keeping the old mowers going.

I'll look for one. ..... Sure wish I'd had one a few days ago. It would have made my Lawn Boy repair adventure a lot easier and less time consuming. I've learned a lot.

Apr 9, 2012#13

Gene123

hankthecrank said:
1 preset altitude needle 1/2 turn from seat
2 start and let warm for 3-5 min.
3 place speed control to low
4 slowly turn needle CCW until engine running smoothly
5 place control to high, if not running smoothly turn CCW 1/8 turns at time till smooth
6 shut-off and immediately try to restart, DO NOT PRIME, should start within a couple pulls at both
low and high settings, if not contitnue turning needle 1/8 turns CCW to obtain easy starting.

This is from manual, good luck, looks like everyone pretty much have it covered. Fuel+ Air+Combustion+Ignition=VROOOOOM.

Thanks, Hankthecrank. ..... Great to get such precise information. You mention an altitude needle. My carb doesn't have one. That confused me. Instead, it has an "adjustable fuel flow needle valve" on the top. Finally, I ferreted out information on the internet saying Lawn Boy made the model 5247 from 1978 - 1982. During that time, they used three different carbs on the F100 engine. The first two had the altitude adjustment screw. The third carb (mine) has the "adjustable fuel flow needle valve."
I'm going to fiddle with adjusting it as soon as it stops raining. ..... Got the feeling I may get lucky and "get 'er done." :laughing:

Apr 9, 2012#14

Two-Stroke

hankthecrank said:
1 preset altitude needle 1/2 turn from seat
2 start and let warm for 3-5 min.
3 place speed control to low
4 slowly turn needle CCW until engine running smoothly
5 place control to high, if not running smoothly turn CCW 1/8 turns at time till smooth
6 shut-off and immediately try to restart, DO NOT PRIME, should start within a couple pulls at both
low and high settings, if not contitnue turning needle 1/8 turns CCW to obtain easy starting.

This is from manual, good luck, looks like everyone pretty much have it covered. Fuel+ Air+Combustion+Ignition=VROOOOOM.

Thanks, hankthecrank, it's always good to know how to do things by the book. :biggrin:

But I have always tuned two-cycle engines under full load (in this case that would be cutting grass.) Maybe the spinning blade is like an airplane propeller which puts enough drag on the engine to approximate a full load.

Apr 9, 2012#15

Two-Stroke

Gene123 said:
Thanks, Hankthecrank. ..... Great to get such precise information. You mention an altitude needle. My carb doesn't have one. That confused me. Instead, it has an "adjustable fuel flow needle valve" on the top. Finally, I ferreted out information on the internet saying Lawn Boy made the model 5247 from 1978 - 1982. During that time, they used three different carbs on the F100 engine. The first two had the altitude adjustment screw. The third carb (mine) has the "adjustable fuel flow needle valve."
I'm going to fiddle with adjusting it as soon as it stops raining. ..... Got the feeling I may get lucky and "get 'er done." :laughing:

I think all of the carbs we're talking about have only one needle valve which adjusts the fuel/air mixture. So don't worry about the different terms -- they're talking about the same thing.

As hankthecrank said (quoting the manual), start 1/2 turn out from the seat -- so cancel what I said about starting one full turn out from the seat. :ashamed:

Apr 9, 2012#16

Fireman 123

Maybe I'm missing the concept, but I can't imagine adjusting the carb while mowing at the same time. My arm isn't that long haha?

Apr 9, 2012#17

Two-Stroke

Fireman 123 said:
Maybe I'm missing the concept, but I can't imagine adjusting the carb while mowing at the same time. My arm isn't that long haha?

It's trial and error. Try one setting and cut some grass... then turn the screw in 1/8 of a turn and cut some more... see if it improves or gets worse. Repeat until you find the best setting.

The point is that a two-cycle engine needs to be tuned fully warmed up and under load -- and I might add that the propeller effect of the blade might provide enough drag so it's not really necessary to test the mower on grass.

:laughing: I can't tell for sure if your question was meant as a joke. The internet is like that. :laughing:

Apr 9, 2012#18

Gene123

Gene123 said:
I'll look for one. ..... Sure wish I'd had one a few days ago. It would have made my Lawn Boy repair adventure a lot easier and less time consuming. I've learned a lot.

Fireman, I checked eBay. There are 135 manuals about Lawn Boys. Since you have a model similar to mine, I'm wondering if you know the title of a manual like you mentioned. For my cars, I've always bought the oem service manual. Is there an oem service manual for just about any Lawn Boy? I'd sure like to find one for my model 5247, a 19" push model made in 1980. As I mentioned, I've got two 5247's ----- one on the verge of running right (thanks to the guys on the forum :thumbsup

and one that has only 35 lbs compression and needs lots of help.

Apr 9, 2012#19

Fireman 123

There's one that covers the older d400-600 series, f-series, and the then new compliance mowers. That's what I have, and what you need. Good luck!

Apr 9, 2012#20

Two-Stroke

About manuals.. here's a link to a page with links to lots of LB manuals available for free download:

LAWN-BOY SERVICE MANUAL 1950-88 (FORM 492-4608, INTERNET REVISION)

Apr 9, 2012#21

Gene123

Two-Stroke said:
About manuals.. here's a link to a page with links to lots of LB manuals available for free download:

LAWN-BOY SERVICE MANUAL 1950-88 (FORM 492-4608, INTERNET REVISION)

Two-Stroke ----- I sure appreciate that !

Apr 11, 2012#22

Gene123

Fireman 123 said:
There's one that covers the older d400-600 series, f-series, and the then new compliance mowers. That's what I have, and what you need. Good luck!

Fireman, tonight I purchased on eBay the manual you recommended. It ought to get here is one week. Thanks for telling me about it.

Apr 12, 2012#23

Fireman 123

You're welcome

Apr 16, 2012#24

S

slippery

If this is the same, only way to restart these lawnboy's is to put throttle in choke and she fires up fine. I guess it was design intent.

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5247 (1980) won't restart. Carb adjustment problems?

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