Briggs 42A707 won't keep running

Hello,
I have an MTD riding mower (model 13AK608G129) with a Briggs 17 hp twin cylinder engine (model 42A707). This mower was left on property that I bought two years ago. It was in pretty bad shape having been left out in our wet northwest winter. I found the owner’s manual and the engine parts list and diagram online. I worked on it last summer replacing the battery, sparkplugs, changed the oil, cleaned the fuel tank, replaced the fuel filter and rebuilt the carburetor with a kit. I also replaced the deck and drive belts and two flat tires. The engine surged some when idling but seemed to run fine at full power under load. I used it to mow my 2 ½ acres once a week for most of the summer. I stored it without gas for the winter by letting it run until the engine died.
This spring I filled it with fresh gas and it started right up. However it seems to have developed a new issue that I haven’t been able to resolve. I can start it and mow but then the engine starts to stagger, loses power and dies. The engine will turnover but not start unless it sits for an hour or so. Then it will start and go through the same sequence. Sometimes it will run for 2 minutes but it has run for as long as 30 – 40 minutes and I can actually get some mowing done. I’ve loosened the fuel cap when it’s struggling and there is no change, the engine still dies. It doesn’t seem that the engine is overheating and I’ve checked the cooling fins around the engine and under the shroud for debris buildup just in case.
After poking around online I found mention that the “ignition module” could be bad and so went out and bought and replaced it. Mind you I didn’t have feeler gauges for the proper gap for the flywheel clearance but I gauged three index cards was about right. It started right up and the surging it has always done was gone. With the new ignition module the engine sounded really nice and smooth at any speed and I thought I had the issue licked. I took it out to mow and it died about 30 minutes later and wouldn’t start. So I am back to square one with the same stubborn issue I had at the beginning. It’s hard to get much mowing done when I don’t know how long it’ll run or where it’s going to die at. I got so frustrated with it when it died this last time that I left it out in the field overnight because it’s just too heavy for me to push up to the garage. Next morning it started right up and sounded fine…..again. I drove it up to the garage and parked it.
I have some mechanical knowledge because I’m a farm gal. My Dad taught me to change oil and flat tires when I first started driving a car and always told me that if you’re running equipment you better know how to fix it too. I’ve built my own computers and wish this mower ran as well as they did. I’m at my wits end with this machine and really hoping that you folks have some ideas that might help.

 

The problem is a dirty carb. I know you ran it dry, but today's gas is crap. It is only good for 30 days. There is always a couple of tiny drops left in the carb, just enough to partially plug the feul passages. Try running some SeaFoam thru it. Can be found at most auto parts store. 1oz. per gallon. If that doesn't work, a carb cleaning is needed.

 

I was thinking of revisiting that carb!! And for good measure I'm draining the gas tank and getting new hoses, filter and clamps as well. I noticed the other day one of the hoses looks cracked and it has those little spring clamps that i detest on anything, could be sucking some air there.
I'll let you know if that fixes it.
Thanks

 

I think your new hoses will fix it. Often when fuel lines are old and cracked, that is an indication that the inner hose is also going bad. The fuel line has a harder outer lining, and a soft inner lining. The outer lining cracks and splits when it gets old. The softer inner lining gets softer, swells, and gets gummy. This swells enough to restrict the flow of fuel, and cause problems like you're experiencing.

 

I got the seafoam on the way to work this morning. I'll get it in there tonight.
Tomorrow I'm off work so I'll be getting those fuel lines taken care of. The one from the gas tank to the fuel filter is a black rubber/fiber type covered in some kind of thick insulation. It sits right behind the engine. On the other side of the fuel filter is a clear plastic type line that runs to the carb. I'm going to replace them both and the filter as well. This engine was parked when I bought this place and had fuel in it from who knows how long. It was pretty gummied up and had water in it as well from sitting out in our wonderful northwest winter. I thought I got it cleaned up pretty well last summer but may not have done as good a job as I thought.
Wish me luck and I'll post back on Thrusday to let you know how it goes.
Thank you both!!

 

The Seafoam didn't work. I put some in the gas tank and a little in the carb while the engine was running. Turned the engine off and let it sit for about 10 minutes. Restarted it and after the smoke cleared took it out to mow. It ran fine for about 15 minutes then started to choke. Difference was this time it didn't die completely. It would run at idle but not full speed. As soon as I gave it more throttle it would start sputtering like it was going to die. I drove it back up to the garage slowly on idle. At least I didn't have to leave it out in the field.
That was on Tuesday. I drained the gas out of it and was surprised to see some small debris in the bottom of the tank. So.......thinking it could be a fuel issue after all I decided to start from the ground up and give it all a good cleaning. I removed the fender and hood to get access to the bottom of the fuel tank and better access to the carb. I removed the entire fuel line from tank to carb and threw it away. I flushed out the fuel tank and verified that the outlet port was not blocked. I removed the carb, disassembled it and soaked it in solvent over night. There had been some small particles in the bottom of the carb body when I took it apart. While that was soaking I went to town to our local mow shop. I was going to get new carb gaskets or maybe a new rebuild kit but they didn't have any in stock. The fellow who works in the shop was very nice to take time to help me while they were so busy. He stated that fuel line should be solid 1/4 rubber from tank to carb and not have any of the clear plastic type line on it. He also said if I was careful when I took the old gaskets off if they weren't torn I could probably reuse them. He said its a large engine and they don't get requests for parts for that type very often. It would be about a week if he ordered them. I got new 1/4 fuel line and a new fuel filter and went home.
Next day I took the carb out of the solvent and blew out the passages with my air compressor. I had been careful when I dissassembled it and the gaskets looked in pretty good shape. I don't like reusing them but didn't have a choice at this point. I reassembled the carb, put everything back together with new 1/4 fuel line all the way from tank to carb and a new fuel filter. When I put gas in it I used a funnel and coffee filter to screen the gas to ensure I didn't recontaminate it with something that could've been in my gas can. With my fingers crossed I turned it over a couple of times and then it fired up.
Once again the engine sounds just fine.....no sputtering, smoking or choking. I figured after all that if it died again it certainly wasn't a fuel issue.
I took it out to mow and kept on mowing for 3 hours.
I had to quit because I was getting tired of driving it around, the machine was still running just fine.
I want to thank you both for pointing me in the right direction. It certainly couldv'e been the fuel lines, the debris in the tank or just a dirty carb. I think both of you were right on target and really really apprecate your help getting this machine running. I finished mowing my place later that day and now it looks so nice!!

 

Good job MossyRockGal Greetings from La Center

 

Glad we could help and good to hear you got it running. Need any more help, just ask.

 

I do have some other questions if you don't mind.
1) Now that I know it runs I'd like to put new blades on it. I tried last summer but the nuts are rusted right to the bolts. I put penetrating oil on them and let it soak but I still wasn't strong enough to budge those nuts. I sharpened the blades last summer with a stone that I put in my drill while they were still on the deck. I figured that was better then nothing but I'd like to swap them out. They are so dull you can't hardly tell the front from the back and I think it makes the engine work harder then it has to. Also if the grass is tall or thick it leaves some standing.....kinda looks like a mohawk haircut, lol. Any ideas?

2). What do you know about this engine? The guy at the mow shop said they don't have much demand for parts and that makes me think its old and obsolete. If it needs more work are parts available for it? Would it be worth rebuilding if it came to that?

3). What should I do to store it this coming winter so I don't need to go thorugh all this again?
Now aren't you sorry you said I could ask

 

1). Blades. Many of us have an air impact gun that takes those blades off with no problem. I am sure you do not. Know a strong male friend? Cook him a nice supper and he will replace the blades for you. I would use "never-seize" when replacing. Just make sure the bolt is tight.
Can't find a strong man? You can wedge a board in the blade so they don't turn, get a 4 ft cast iron pipe the will fit over the handle of the breaker bar, then push (or pull, which ever is easier for you). The added leverage usually does the trick. You could also pull the tractor near the wall so you can lean against the wall in a sitting postion and use your legs. Legs are stronger than arms.

2). Engine is NOT old or obsolete. The tractor is a 2000. Would need the engine code number to see what year the enginie is.
They probably don't have much of a demand for parts only due to your location. Certain makes are popular in certain areas. I thought Ariens was popular all over the country. Some mechanics here have never worked on an Ariens due to they are no dealers in their area making them not very popular.
For tractor part numbers, go to
buymtdonline.com.
Need engine part numbers, I (along with many others here) can get you those, too.

3). Winter storage. In the last tank of gas, mix Isopropel Drygas 2oz. per gallon. Buy some Sta-Bil. Stabil just came out with a formula made especially for E-10 gas (10% ethonal). This is more expensive right now as it is marketed mainly for boats and is in a quart container that treats 320 gallons gas. If you can't find this, use regular Stabil at 2oz. per gallon. Run the engine for 15 mins. varying the throttle to make sure you get Stabil thru both the high & low speed circuts of the carb.
I have in-line gas shut offs on my snowblower & lawn tractor. After running for 15 mins, I shut off the gas and let it die. What little gas that is left in the carb has Sta-bil & dry gas in it.
Then I drain the gas out of the tank and use it in my snowblower, or my truck. So now, in the spring, I get fresh gass to start the season off.

Am I sorry I asked? NO!!

 

Thank you for all your help.
The engine was built in 1999. I did find the date code on it and how to decipher it at the briggs and stratton website. How long do these engines typically last if they are taken care of? I've never had a riding mower before and would like this one to last as long as possible. It certainly has been educational fixing, repairing and learning about it. I'm glad to know that its not obsolete as I first thought. Seems like everyone around here has riding mowers but they appear to be smaller and not as powerful as this one is. Maybe those are the ones that are more popular in this area.
Unfortunately my male friends are not very many or strong and have a tendency to avoid my little farm.......must've been that post hole digging we did last summer in my rocky ground I did cook them a good dinner but I don't think it made up for the blisters or aching backs, although we did get the fence up!! I will try a pry bar for leverage and see if that will work. I've worked with stubborn stuck things before and sometimes it just takes patience.
I will make sure to use sta-bil and the gas additive this winter so the carb stays clean.
Once again thank you for all your help. It’s a great pleasure to find folks that are willing to share their knowledge to help others and I really do appreciate it very much.

 

The engines, like your car engine, will last a long time with the proper maintaince. I just sold my old 1975 Montgomery Wards lawn tractor a couple weeks ago. Had a 10hp Briggs engine. It had started smoking & using oil, the choke valve was worn, but mostly, it was underpowered for cleaning leaves in the fall. In 1975, 10 & 12 hp engines were on the bigger side. Many used 7 & 8 hp engines. Yes, I could have fixed it, all the parts I needed for it are still availabe. In all honesty, I wanted an excuse to buy a new tractor with a bigger engine along with other features that were not avaiable (or even thought of) in 1975.

 

The mower has been running fine since my last post. Except for yesterday I mowed for about 45 minutes when the engine started to stutter at full power under load. I shut down the blades but still stumbling. Throttled back and idle was ok. Drove it up to the garage and parked it. It was a little warm but didn't seem excessively hot.
I left it for several hours while I went and did some other chores. When I came back I tried to start it. Cranked but didn't catch. I was thinking it was the fuel issue again so trickled a little gas into the carb throat. Cranked, but no start. Didn't even try. I sprayed a little starting fluid into the spark plug ports and the carb. Cranked it and same issue. It turns over fine but not even trying to start.
At this point it didn't seem to be a fuel issue so I pulled a plug and checked for spark. None. I replaced the ignition module earlier so figured it wasn't that. I disconnected the ground wire from the ignition module and checked for spark again. Now it's got spark. Replaced the spark plug and it started up and ran just fine.
Of course without the ground wire connected to the ignition module I have no safety switches and I couldn't turn it off with the key either I got it off by reconnecting the ground wire. Everything I've read states that if the mower runs like this it is a bad safety switch and to check them all. But there aren't specific instructions on how to check the switches. What do I need to do to see if a switch is good or not? Is it likely that it’s not a switch?
Also when I was working with the fuel issue I found some wires that are just cut off. They are near the clutch pedal but behind the fender that I took off to get to the gas tank. The colors are solid yellow, solid red and solid black. I don't know what they originally went to or if they are part of the now existing electrical issue.
Once again any help is vastly appreciated.

 

With the kill wire reconnected to the coil you have no spark again, correct? If so, it could be a safety switch, ignition switch, or one of the wires you mentioned that are cut. Do you have an ohmmeter?

 

Correct. When I reconnect the ground wire to the ignition module there is no spark. Its a new ignition module that I just put on there about 3 weeks ago. I'm going to take another look at it and make sure that I installed it securely.
I do have a volt/ohm meter somewhere. Thats not something I use a lot. I can tell you that the one I have is older then the hills. Not a digital model like the ones I see around now. I probably can put my hands on it though, I've got a pretty good idea where its hiding at. What should I do with it when I find it?

 

Set it to the lowest ohm setting and connect one lead to the kill wire, and the other to the negative battery terminal. It will read near zero. Now, turn the ignition switch on, lock the brake pedal down, and turn the blade handle off. If it still says near zero, then unplug a safety switch at a time until you find the one that allows the ohmmeter to read at the other end of the scale when you unplug it. That would be the culprit switch.

 

Ok. I'll give that a try and see what happens.
I'm off work until July 5th so I will post back then and let you know what I find.
Thank you for your help. This mower is turning into a fix and repair daily kind of machine.

 

I didn't have time over the weekend to fuss with the mower. To many other things demanding my time I did fiddle with it for a bit. It won't start at all now. Turns over but dosen't engage. Even if I take the kill wire off it still won't start. I didn't get a chance to check for spark but thinking there isn't any. I'm going to check it out as soon as I can. I'm going to have to! The grass hasn't stopped growing even though our weather has been warm and dry.

 

I apologize for being away for so long. Life can just throw a whole bunch of stuff at you sometimes.
I did finally get back to the mower. It had been awhile since I looked at it so started from the beginning.
It cranks, but will not start. It does have spark, with and without the kill wire connected, on both plugs.
Funny thing is that when I was checking for spark I had one of the plugs out, held it close to the engine and cranked the engine. When I cranked I could see the spark at the plug, but also from the body of the plug to the engine. It actually tried to start. I'm wondering if that indicates a safety switch still or a bad coil?
I haven't tested all the safety switchs but if you think that is still what the problem is I will go after them.
I was beginning to think that the whole thing was just shot, bad engine or internal engine issue. But since it tried to start with the last 'spark' test I did I'm more convinced it is an electrical issue.
Any ideas would be appreciated and I will try to stay on top of it this time. Thanks

 

The thing you saw at the plug/spark doesn't indicate anything other than you have a good ignition module. When you check for spark you should have the plug casing well grounded to the engine. If not, it will either do what you saw yours do or not spark at all.

 

Ok. But thats the first time its tried to start. Maybe just a fluke. Any other ideas?

 

To get on the same page, you have a twin, you got it to run, it has quit running, and you are working on the safety switch possibilities as ignition problems.

You have spark, but you pulled one plug and apparently the engine fired and tried to start? Was it firing on the cylinder you have the plug out of or the opposite cylinder.

I would say just a fluke, but it's better than nothing.

When you have the kill wire disconnected, where did you disconnect it? Some of those have one coil with two high tension leads for the plugs, and some have two coils with a juncture for the kill wire.

 

Yes. I have a twin. I did get it running. Then it quit. Its been parked for a bit as I got tangled up in other things and didn't have time to pursue it.
When it tried to start it was the opposite cylinder that tried to fire up. But at least a sign of life. Otherwise it cranks over just fine but doesn't even try to start.
It does have spark with and without the kill wire connected. I've been disconnecting it from the ignition module. The wire runs from the ignition module to a push type connector and then into the wiring harness. I've been taking the connector apart to disconnect it.
Any help getting this mower running again would be appreciated. Its been a mess, parked for a long bit outside. If you read previous posts you will see the fuel issue it had originally. Now this is something else entirely and I'm not that good with electrical issues

 

Leave the kill disconnected at the module for now and......

Try putting a teaspoon of fuel directly into each cylinder. Then with no choke and half throttle see if it'll start.

If it doesn't fire at all, either disconnect the fuel line from the carburetor or shut the fuel off at the tank, pull both plugs and spin the engine over about ten times with full throttle and no choke. This will purge the fuel if you have a flooded condition.

Then add a teaspoon of gas to the cylinders and see if it'll try to start with half throttle and no choke. It won't run long if it tries. If it does try to start, hook up your fuel again and try to start it with no choke and half throttle.

 

MossyRockGal101: Replying to an earlier post of yours, While Briggs & Stratton no longer makes your type of engine, they do still support it. Those old Briggs opposed-twins are like GOLD! Reason is that they were very reliable if taken proper care of, and they produced very smooth power. Unlike the more modern V-Twins, which are odd-fire, the opposed-twins are even-fire, meaning their cylinder firings are evenly spaced throughout the entire 4-stroke cycle.

V-twins, by contrast, still have two firings per four stroke cycle, but are not evenly spaced, resulting in an idle and operation with the smoothness more of a single-cylinder engine.

If your tractor eventually dies and the engine is still good, either sell it for top dollar, or find something else for it to do, like power another tractor, go-kart, generator, whatever. I have a 19.5 hp Twin-II, and I love it! Wouldn't part with it for all the tea in China.

Gud Luck,

Steve