Briggs & Stratton 16.5 HP Tractor: It's Possessed. Arrrggghhhhhh!

[dogsdad]

I have a "Yard Machine" lawn tractor powered by the above mentioned motor.<br /><br />Cutting the grass today, I was just finishing up when suddenly the tractor felt as though it had lost about 25% of its power. Then it died, and it wouldn't start. Evidently, I had the throttle wide-open at that point. I checked it for a clogged fuel filter (fuel flow is good) and tried to see if it had spark. It seemed to have no spark at all, so I began investigating the ignition system on line.<br /><br />I came to a point where I needed the model number, so I went out to check it and decided to give it a crank and see if it could be a heat related problem. With the throttle almost shut, the darned thing started up, but would only run at lower RPMs. At least I could drive it back to the shed, but I had to keep it in first gear because it has very little power and cuts out at higher RPMs.<br /><br />I'm thinking maybe the governor is screwed up, but I am only guessing at this point. And if I can rely on the collective knowledge of everyone here at iboats and find out what's wrong without a lot of piddling, I would be grateful!<br /><br />Thanks!<br /><br /><br />-dd-

 

[sangerwaker]

Re: Briggs & Stratton 16.5 HP Tractor: It's Possessed. Arrrggghhhhhh!

Check the air filter. My lawn mower did something similar and it was only a VERY plugged filter. Doesn't hurt to clean them once in a while anyway. Hope it works!<br /><br />Doug

 

[ehenry]

Re: Briggs & Stratton 16.5 HP Tractor: It's Possessed. Arrrggghhhhhh!

Check the key on the flywheel. Sounds like to me you might have broken it and its out of time a little bit.

 

[eurolarva]

Re: Briggs & Stratton 16.5 HP Tractor: It's Possessed. Arrrggghhhhhh!

If the governor is still attached by the spring chances are pretty good there is nothing wrong with it. If you choose to take the carb off and clean it make sure you diagram how the governor is hooked up. If you have a digital camera take pictures. I have had many motors apart and then trying to figure how the governor hooks up is a challange. I dont know if briggs has this but on the techumseh engines on the bottom of the carb is a brass screw. This screw is the carbs main jet and by removing it and cleaning it the fuel problems usually go away. There are tiny holes on either side which need to be cleaned with a wire and carb cleaner. Chances are you got some bad gas. Test the spark by taking the plug out of the cylinder, Keep the wire connected and ground the tip of the plug and try starting it. Do it in a dark place. If you have a blue spark chances are it aint the plug<br /><br />When it runs at slow speed does it back fire?

 

[Bob_VT]

Re: Briggs & Stratton 16.5 HP Tractor: It's Possessed. Arrrggghhhhhh!

Check your oil. Many lawn motor motors are equipped with oil sensors that prevent starting if there is low oil.<br /><br />Bob

 

[ED21]

Re: Briggs & Stratton 16.5 HP Tractor: It's Possessed. Arrrggghhhhhh!

The magneto coil on my tractor went bad. It would quit then start after cooling off. <br />I didn't have the low power/cutting off at high speeds, just run or not run, but coil or magneto could be failing.<br />Check for a good spark and if spark is erratic when it acts up. Not sure how to do that, maybe an inductive timing light might show something.

 

[norman158]

Re: Briggs & Stratton 16.5 HP Tractor: It's Possessed. Arrrggghhhhhh!

how old is it? model type and date code would help

 

[dogsdad]

Re: Briggs & Stratton 16.5 HP Tractor: It's Possessed. Arrrggghhhhhh!

Norm, it's a model 42A707. I think it's about three years old, but I really don't know.<br /><br />I like Ed's suggestion of using an inductive timing light to monitor the ignition. That's how I check out my Merc 135 outboard from time to time...dunno why it didn't occur to me to use it on the tractor!<br /><br />Also, I have checked the oil and cleaned the air filter<br /><br />Thanks for all the help and suggestions so far, guys!<br /><br /><br />-dd-

 

[boatneck]

Re: Briggs & Stratton 16.5 HP Tractor: It's Possessed. Arrrggghhhhhh!

If you're still having trouble, it may be the carburetor. I had a Sears 18 HP B&S that exhibited loss of power, etc. Turned out it was dirt in the fuel float bowl. Cleaned it out, and it ran like a champ.

 

[norman158]

Re: Briggs & Stratton 16.5 HP Tractor: It's Possessed. Arrrggghhhhhh!

thats briggs tried and true twin, give it a new set of plugs and clean the carb real good

 

[dogsdad]

Re: Briggs & Stratton 16.5 HP Tractor: It's Possessed. Arrrggghhhhhh!

Okay...I've looked at it today. <br /><br />I disassembled the fuel pump portion of the carburetor. Interesting little mechanism, it is. I wasn't prepared for the springs that fell out, but it wasn't too difficult to figure out what they were for and how they work...<br /><br />Anyway, there was no residue or anything wrong with the carb. So, I ran the motor with all the fairing and air cleaner parts removed so I could see what was happening. What I found was that the governor was flipping the throttle plate wide open, and the motor would die.<br /><br />I played with the governor adjustment and got the thing back to where the power seems right again and it will run under load. I guess the adjustment screw just backed out due to vibration or something, or maybe the previous owner fiddled with it and had it misadjusted.<br /><br />Thanks for all the suggestions and help!<br /><br /><br />-dd-

 

[dogsdad]

Re: Briggs & Stratton 16.5 HP Tractor: It's Possessed. Arrrggghhhhhh!

Oh no, oh no, oh NO!<br /><br />I thought the thing was back on its feet---errr, wheels---but it's still acting up!<br /><br />I think I'll follow norman158's advice first. In my experience, it pays to try the simple stuff first, and it makes sense that if there's a lack of power due to failing plugs or something like that, the governor will try to make up for it by pouring the coals to it. Which explains the throttle popping wide open. Hmmm...<br /><br />I looked at the plugs and they are not particilarly eroded or worn, but thet are carboned up pretty good. I'll try new plugs and plug leads first.<br /><br /><br />-dd-

 

[gspig]

Re: Briggs & Stratton 16.5 HP Tractor: It's Possessed. Arrrggghhhhhh!

Check the fuel tank vent. My JD would run fine for about 15 min then sputter and die. After a few min it would run again. I could lengthen the die off time by choking the engine. I found that the tank vent was plugged. No problem for over a year.

 

[dogsdad]

Re: Briggs & Stratton 16.5 HP Tractor: It's Possessed. Arrrggghhhhhh!

I put new plugs in the motor this morning and fired the tractor up. I knew right off it still was not right, but it was running well enough that I went ahead and cut most of my yard. When it was time to stop and put more gas in the tank, I did so and the thing wouldn't start again. I could see fuel going down the throat of the carb, so I got my inductive timing light out and found there was no spark. I pulled the shrouding off and fiddled with the coil, and the motor would then start, but again I knew it wasn't right. I decided to leave all the shrouding of because I believed that the coil was at fault and plan to replace it. As I was parking it in the shed, which is fairly dark inside, I noticed arcing in the coil assembly. I am even more convinced that the coil is faulty now.<br /><br />Someone please confirm this, or set me straight: it appears that the ignition switch actually kills the coil output to stop the engine, rather than energize it to make it run. It looks to me like the coil is a self-contained ignition system that requires no input other than a magnetic pulse from the flywheel. Is that correct?<br /><br />I am also convinced that the reason that the governor was flipping the throttle wide-open was due to loss of power (and RPMs) caused by the faulty coil. Can anyone confirm or refute that?<br /><br />Thanks!<br /><br /><br />-dd-

 

[Kenneth Brown]

Re: Briggs & Stratton 16.5 HP Tractor: It's Possessed. Arrrggghhhhhh!

You are correct about the ign cutting power off. The theory about the governer sounds good too.

 

[ED21]

Re: Briggs & Stratton 16.5 HP Tractor: It's Possessed. Arrrggghhhhhh!

That's how mine works too.<br />New coil cost me $42.<br />While you have the shrouds off, check the cooling fins for blockage & dust buildup.

 

[dogsdad]

Re: Briggs & Stratton 16.5 HP Tractor: It's Possessed. Arrrggghhhhhh!

Replaced the coil. Had to play with the governor adjustment screw a bit, but the tractor now runs like it did before all this started.<br /><br />Thanks for all the help and suggestions!<br /><br /><br />-dd-

 

[dogsdad]

Re: Briggs & Stratton 16.5 HP Tractor: It's Possessed. Arrrggghhhhhh!

I can't believe this.<br /><br />The new coil? It went bad. Or maybe it went bad... I don't know anymore!<br /><br />The tractor ran fine after I replaced the coil. Then just a couple days later, I was out doing some serious grasscutting, and the d***** thing died, just outa the clear blue. Being a bright sunny day, it's hard to be sure, but it looked as though I was getting no spark again. Hmmm.<br /><br />So, I put the old coil back on, and it fired right up. I put silicone all over it to keep the arcing to a minimum. Then I boxed the new [failed] coil back to the good folks I bought it from, and they sent a new back to me.<br /><br />I installed the second new coil this morning, and the tractor fired right up. So off I go, a-cuttin' grass again. After about two hours (big yard), the thing dies on me AGAIN.<br /><br />I learned in the electronics game that you don't keep replacing the same component over and over again. You look under the bed once, maybe twice for a pair of shoes, but if they ain't there, they AIN'T THERE.<br /><br />This ignition system is so rock-simple, I don't see how it can fail unless the magneto/coil takes the proverbial dump. I can see the fuel being sprayed down the carb. I know it's getting fuel.<br /><br />Okay. I am getting spark. I am getting fuel. If it doesn't run, then it's got to be a cam timing thing, right? But how in tarnation does the cam timing go bad, then fix itself, then go bad, then fix itself, repeatedly?<br /><br />So now I am snooping in the exploded view of the motor. Lo and behold, horrors upon horrors, I see that the camshaft is gear driven, and that there is a key that indexes the crankshaft to the camshaft drive gear. In my overstressed imagination, the key is damaged, the camshaft drive gear is slipping periodically and throwing the timing all outa whack, and then when the gear has slipped 360 degrees, then it catches again---for a while--and the tractor runs for a bit.<br /><br />There are demons in my tractor.<br /><br />Well, maybe not. Maybe I am overlooking the stupidest, simplest thing. Can anyone out there corroborate my hypothesis, or refute it?<br /><br />Pleeeease! My sanity us at stake. I may just go buy a new John Deere tomorrow and try to give the ol' piece o' junk away!<br /><br /><br />-dd-

 

[starrider_68]

Re: Briggs & Stratton 16.5 HP Tractor: It's Possessed. Arrrggghhhhhh!

there may be another cause...under the flywheel there is an electronic componet that now replaces the old "points and condencer" that regulates the spark on small engines..if it is worn out (and sounds like it is) then you need to pull the flywheel off and replace it. it should cost @15.00 - 20.00 for it. That should take care of the problem

 

[SS MAYFLOAT]

Re: Briggs & Stratton 16.5 HP Tractor: It's Possessed. Arrrggghhhhhh!

Sounds like it could be a bad ignition switch to me. If it has corroded contacts, it make be okay when it is cooled off, but after the contacts get warm, they maybe opening up partially and not allowing full current to pass through.<br /><br />Just a thought, and with electronic ignition, a bad switch can cause other components to go bad.