[Titus]

I'm still scratching my head with this one. From my bush hog D4-7. Finally got it to turn over and now it's not starting. Fresh battery, new spark plug, fuel, carb cleaner, engine starting spray, nothing. It just keeps turnin and turnin.

From all of that (not being a master of engines by any means), I would assume it's not getting a spark, no spark not from lack of fuel. So the distributor maybe? No power to that?

What do you guys think? Thank you all for your time.

 

[bstrucker]

On an S7D there is no distributor,just a magneto that the spark comes from,if you lay the plug on the head with the sparkplug wire connected to it,you should be able to see a spark jump the plug gap.If you don't have spark,which does sound likely,the first thing to do is clean and reset the points,they are in a little box under the carb near the bottom of the engine.If you take the cover off,you'll see the points,make sure they aren't oil soaked,that the points are shiny and the contact surface is flat,you can file them flat and shiny with an emory board.After your sure they are clean put them back in and set the gap to.020,then check your spark again.

 

[Titus]

Checked all of that and thank you for posting that info. Without that post I wouldn't have tried that. I have a spark and all the wires are good.

At this point I'm a little lost. Almost got it to kick over. Playing with the tiny throttle knob behind the carb while spraying starting spray into the carb that's almost all the way choked has almost gotten her to kick over. She wants to, but isn't. Even with straight fuel I'm not getting her to kick over.

What am I missing here? Thank you again!

 

[bstrucker]

If your sure you've got spark and it won't start by spraying starting fluid in the carb or putting a little gas right into the cylinder,then you need to see how good your compression is.The most common problem that I've found on those old Wisconsin engines is the exhaust valve being stuck open,if the engine has been sitting for awhile,it's a possibility.After that,there is a chance that the rings are stuck in the ring grooves and won't let the piston build enough compression.Has the engine been sitting for awhile?

 

[Kbeitz]

On an S7D there is no distributor,just a magneto that the spark comes from,if you lay the plug on the head with the sparkplug wire connected to it,you should be able to see a spark jump the plug gap.If you don't have spark,which does sound likely,the first thing to do is clean and reset the points,they are in a little box under the carb near the bottom of the engine.If you take the cover off,you'll see the points,make sure they aren't oil soaked,that the points are shiny and the contact surface is flat,you can file them flat and shiny with an emory board.After your sure they are clean put them back in and set the gap to.020,then check your spark again.

I do have a distributor for one...

 

[Titus]

I was told it wasn't running for a few years. I could hand turn it on the PTO in the front. When I took the top of the engine off I saw the two valves and they are opening and closing fine.

After fiddling with it yesterday I think it's a matter of timing. The choke to the throttle control. Is there a way you could take a photo and post it of your throttle control assembly on the right side of the motor for me? The Governor lever too? I'd like to make sure that's all assembled correctly before moving on.

Thank you!

 

[Fcubman]

My old Wisconsin sat for quite a while and wouldn't start. The valves opened and closed fine by eye - but - the exhaust valve wasn't quite seating and the seat was rusted. I had to adjust the valve clearance and lap the valves.
Lesson learned: check the compression, don't just eyeball it.
I wasted a lot of time until I discovered the exhaust valve problem.

 

[Tractor-Holic]

When you pull it over you should hear a "clack" coming from the magneto,that is a spring loaded impulse coupling that spins the magneto shaft rapidly to give it a hotter spark for starting..the points have to be set properly,turn the engine slow by hand and watch the points--when they open to the widest gap,that is where the engine needs to be at,when setting the gap,otherwise they wont open at the correct time or might not ever close...you should see a healthy blue spark each time the impulse coupling "snaps"...
Many Wisconsins used 18mm plugs,and they dont always weather well,might want to try a new plug ,that might be all it needs..I think the SD-7 I had took a D16 Champion...

 

[Titus]

Thanks for the posts and fresh ideas. I've noticed the magneto getting quite warm after several attempts to start her up. I have an electric starter button I push in. I don't hear a clack sound or any sound for that matter coming from the magneto. I have a brand new spark plug in there and I'm getting a good spark coming from it.

I'll take the top off the engine and check the valves.

 

[Fcubman]

You could just check the compression without pulling the head - easier and quicker to do.

If you have a magneto, but it's not making the clacking sound, perhaps the timing is way off. It might still produce a spark if you turn it fast enough, but the ignition timing might be off. You should get a spark even when turning the engine over slowly, even by hand - the impulse mechanism should snap the mag over and produce the spark. The spark should occur somewhere around Top Dead Center. If the impulse is stuck, the spark will occur only when turning the engine over quickly, and well away from TDC.

The mag getting warm is a puzzler. I wonder if it's partially seized up, and friction is causing the heat….???

 

[Titus]

This might be a silly question and I'm sorry for asking but how does one check the compression? What do you mean by TDC? Where is that located? I get the feeling that the timing might be off. Engine sounds like it wants to kick over, but it's just not. Thank you.

 

[Fcubman]

No such thing as a silly question!

To check the compression: one generally uses a compression tester, which is basically a pressure gauge. You can do it without a gauge by removing the spark plug, and holding your thumb over the plug hole while cranking the engine. The engine should rather strongly push your thumb a bit away from the hole. The pressure should be around 80 pounds per square inch or more, but there won't be a lot of volume, so your thumb won't leave your hand. The engine should push your thumb a bit so the compressed air escapes "with authority". (I would ground the spark plug wire to the block to prevent electrical damage to the mag, since creating spark voltage with no place for it to go can do damage to the mag.) A lack of compression will not cause pressure to move your thumb, and has several causes. Most likely is valve leakage. Before taking the engine apart, you might try squirting a bit of oil in the plug hole. That will temporarily seal the rings and boost compression if the rings are bad. I'd to that second. In other words, thumb test your compression, then squirt the oil in and check it again. An improvement indicates leakage around the rings. That might mean worn rings, or just that the rings are dry from sitting around so long. If you notice increased compression, try starting the engine again. Perhaps the increase in compression will be enough to get it running.

Top Dead Center is a position, not an object. TDC refers to the position of the piston in the cylinder bore. When the piston is as high as it goes in the bore, and the crankshaft is centered right under it, that is TDC. If you can see the piston when looking in the spark plug hole, you can see it moving up and down while the crankshaft turns. When the piston is at the top, it is at or near TDC. Most engines have a mark on the flywheel to indicate TDC, since you can't see the crankshaft itself to see when the crank journal is directly centered under the piston.

A fairly accurate means of finding TDC if it's not marked on the flywheel is to observe the piston's travel. Turn the crank until the piston just starts to move down, and mark that point on the flywheel, next to something that is stationary. Then turn the crank the opposite way, and note when the piston starts to move down again. Mark that position. TDC will be between those two marks. This is just an approximation, but may be helpful in determining when your spark should occur.

In your case, I would expect to hear the magneto impulse coupling snap when the piston is at or very near the top of its travel.

I hope I haven't confused you further! Please feel free to ask whatever questions come to mind. That's why we're here!

 

[Titus]

It has compression. It made perfect sense (what you wrote) once I tried it. Turning the engine over by hand I was able to see a spark. The brass piece was slightly exposed when I went to go move it, so I got a nice little zap this morning.

The clack you both keep referring to...would that be coming from the breaker point adjustment box? I see the "push pin". It moves freely however when the motor is turned over, it barely moves. I checked the voltage and it's getting plenty of electricity. Thoughts?

 

[Fcubman]

Now I'm confused…what is the brass piece that you moved? Maybe a picture?

Also - where did you measure the voltage, and how much voltage did you get? I'm beginning to think that you don't have a magneto, you have points and coil ignition. That's a bit different to troubleshoot.

 

[Titus]

The brass piece was from the plug that plugs into the spark plug. Photos here:

 

[Titus]

The bottom two photos are my breaker push pin assembly. I saw this photo:

And as you can see where the breaker points are there is a gap, well there is no gap with mine. I wonder if that closed connection would be causing the problem. I also don't have a spring around the pin that should be there. Is this even the right pin?

 

[Fcubman]

I don't think you have a magneto, you have points-and-coil. Forget what was said about the impulse coupling.

Nice pictures!

The cylinder that the plug wire goes into is your coil. With the points open, there should be battery voltage on both small terminals of the coil. With the points closed, there should be battery voltage on one terminal, and close to 0 volts on the other.
The position of the points is key to this check.

The coil will fire when the points open. You set the timing so that the points are just opening at the correct time, which is somewhere near TDC. You may not be able to adjust the timing directly, the points gap will do that for you.

Unless you have the correct specs, I'd set the points to .025 inch at their maximum opening. The point gap will also affect the timing. The adjustment slot fig. 10 refers to is how you adjust the point gap with a screwdriver, after loosening the lockscrew a bit. There may be a data plate on the engine with the points gap listed.

You will have to turn the engine by hand until the points are open as far as they'll go. If they aren't around .025 inch at the max opening, adjust them.

I don't know about the pin, but if it's opening the points, it's doing the job.

 

[Titus]

When you say points you mean what? One is positive, one negative/ground.


When I took the breaker off, I saw two small holes behind it. I can see what I assume to be the exhaust valve and other valve rods going up and down when I hand turned the motor.

http://www.jacques.lacasse.com/GardenTractor/Info/Engine/Wisconsin/S10-12-14D/Page23-24.htm

I found a similar manual online.

I hope I'm understanding this correctly.

**Edit: When I turn the motor by hand, the pin moves very little, not enough to open the breaker points. They are always together. Even at TDC that pin doesn't move much.

 

[Titus]

And still nothing. Got it set correctly, watched the gap open and close and nothing. I'm not willing to give up, but I'm at a total loss right now.

 

[rscurtis]

It appears that your engine has battery-coil ignition. You can easily test this with a 12V test light. Connect the light between ground (engine block or battery "-", and the terminal on the points box. With the points open and the ignition on, the light should be lit. When the engine is rotated so the points are closed, the light should go out. If it does not, the points are not conducting power and need to be cleaned.

Once you establish that the points are conducting power, you can now manually open them with your finger, and you should have a spark at the plug. If not, the problem is somewhere else, as in the coil, wire, or spark plug itself. If you can hear a spark but not see one, the coil could be at fault. Be sure to turn the ignition off when your finished playing, or the coil will overheat.