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'73 3416 engine problems


MattL

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First-timer here. I've got a 1973 3416h Sovereign that's giving me some problems that I'm hoping someone out there may shed some light on. This is my second simplicity (my first is a '71 3214h that's waiting for a new engine when one is found). Anyways the 3416 seems to have developed a problem----after being run for some time the tractor will suddenly stop (dead stop-very quick) and a puff of smoke exits the carb. The starter cannot move the piston after this happens so I must advance the piston using the belt. Once I advance it it starts right back up again and will run for some time before happening again. I've added some marvel mystery oil to the gas as it appears it might be the valves sticking--hasn't worked. Could the problem be a timing issue? I ask b/c I pulled the engine recently and replaced the piston, rings etc. Thanks for any advise.
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Wow thats a good one. I think with a mystery shutting down problem I would start looking at fuel delivery issues. check the gas cap vent is clear, feel the intake manifold for heat right after it dies it might be vapor lock. make sure the cooling fins are clear under the tin and maybe check the fuel filter for sludge. Thats my 2 cents anyway. With an intermittent problem you really just need to go over the systems and start ruling stuff out untill you find it.
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Could a vapor lock cause the need for the piston to be advanced via the drive belt? I almost think that it could not be vapor lock as my gas cap has a hole in it (can'tleave it out in the rain).
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I was thinking excessive engine heat really more than anything. How hot does the S/G get? Im not really prone to jump at internal engine problems first. I like to start by looking at the easy to get to stuff. I t really could be alot of things. If you think the fuel situation is good then go to electrical. Really with ghost issues that go away as fast as they come you just need to start looking it over and ruling things out. Maybe somebody on here has had the same problem and will chime in tonight or tomorrow.
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i had that problem before one of my rings broke. it marred up the cylinder pretty bad. did you install the right size rings? did you have the right gap in them? my last question is did you do a quick hone on the cylinder before the new piston and rings?
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New rings? Sounds like your rings are too large, and when the engine warms,the piston can't travel, causing the engine to stop. That would also be a problem for the starter to turn over. Or, you may have tightened the rod too tight on the shaft, causing the same problem when the engine gets to operating temp
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The piston/rings came from my local small engine mechanic-they are after-market parts he ordered using my B&S serial number. He set the gaps for me with his ring compressor tool which he lent me to install. I did do a quick hone of the cylinder . Here's the kicker to all this though.....i replaced the piston, rings and rod after the tractor experienced the sudden stop the first time. After this first time I figured I siezed the engine as the oil dipstick showed no oil (yes I'm quite embarassed). Upon tearing it apart the only problem I found was a very small amount of marring on the rod. I thought I was super lucky and that this smal amount of marring had caused the problem so replaced it at that time. So, I'm not positive at all with this sequence of events whether the problem has anything to do with the new rings. Muddier water? Thanks again
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If you have been inside the engine recently I would think it needs to be gone over again. If you have a "sudden stoppage" that requires you to force the piston past some point of rotation before you can start it with the starter I think it is safe to say there is something wrong inside the engine. You mentioned it had "slight marring" of the rod did you turn the crank or at least check it with a micrometer?? You mentioned replacing the piston and rings, did you measure the new parts and check for proper fit in the bore? ie a 10 over piston in a worn bore might fit but certainly not be the correct fit! My money is on the inside of the engine not the outside. To answer you question yes it could be a timing issue but it is VERY VERY unlikely as if it were a timing issue it should not be intermittent and if you are thinking is is a Cam timing issue I would not think so, they are either right or they are not but they are not intermittent.
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Also I don't know of anyway to check or set the ring end gaps using a ring compressor. The entire idea of checking the end gap is that it is done in the engine that they are going to run in. He would have had to have all the dimensions of your engine (measured in 6 places) then had to use a dial bore gauge to set the ring compressor to the same dimensions (in 6 places) then installed the rings one at a time then measure the end gaps then file each one separately and if any mistake was made in measuring or setting up the ring compressor the new rings would be junk! I don't know of 1 reputable mechanic any where that would even attempt this! I am not even sure how you could set the ring compressor to reflect the tapper in your bore?!?
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I have a 3314H with the same engine and had a similar but different problem. If i had to guess i would say that your best option is to leave it for now and the next time that happens leave it to cool down. If it will spin with the starter after then i would say that you have a heat problem. Second thing i would do is think about all the things that could have been screwed up when it happened the first time. The drive shaft could have been warped. The hydro could have been screwed up, gear teeth may have been broken. It isn't necessarily likely but just take everything into consideration. Unfortunately the third thing that i would do is re tear down the engine and re-re-build it. I don't know if this is a stupid question or not but did you put some oil on the rings and the cylinder before you started it after your rebuild?
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Also my engine gets pretty hot and i tend to keep a bit of extra oil in it. Even with the amount of wind it produces it can get really hot. And the timing seems to be very odd with the engine as well. It seems to be off when i just turn it over by hand but when i start it up it runs better than any other engine i have. If i try to start it when it is warm it will backfire through the carb and then start right up. Is it possible that your timing is screwed up by the re0-build?
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Thanks for all of your input. I'm going to restate the sequence of events that led to the engine abruptly stopping.Maybe this would give additional clues. This 16hp Briggs motor came from another tractor and I don't know the history of it.After putting this motor on my tractor it ran perfectly for about 2 hrs and stopped abruptly. When it stopped, a puff of smoke came from the exhaust. The electric starter could not move the crank.I checked the oil and no oil on the dipstick.My first reaction was that the engine seized and I didn't want to do damage to the engine so I tore it down. During engine removal, I remember I was able to turn the crank, hard at first then it was free turning, so I thought maybe damage is not severe.I disassembled the engine and everything looked fine. The piston walls were clean with no score marks and very little ridge.The crank had very little scoring and the crank diameter was measured with a micrometer and it was not out of round.The engine was refitted with a new piston,rings,connecting rod,the walls were rehoned,the piston rings were lubricated and the same problem reappeared.It stops abruptly like it sized,a puff of smoke comes out of the exhaust. I turn the crank which is very hard to get by the sieze point,and the engine restarts.I think this engine was worked on by someone and wondering what the previous mechanic could have done.I believe the problem is internal.Thanks
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I would look at your valve clearances first. Put 10W-30 oil in it [b]ABOVE the full line on the dipstick, not too much but these cast iron briggs do get mighty hot. And then i would check your torques on your head and your oil pan. Im not saying that you did but if you tightened one or two incorrectly or in a circle then it may be offcentered and the crank may be binding up on it. After that if the problem re occurs then run it disconnected from the Hydro and if it dosent occur then its not your engine. Other than that i would re tear down the engine unfortunately.
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I had a 716 that did that and found out that someone had reground the crank and did not get the clearances right to the rod and ended up breaking the rod.
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