Motor Overheating?

[Twayne]

Hi,

This actually goes along with my previous post about Lawn Tractor Battery/Charging issue but experience tells me it's best to separate things like this.

Motor Overheats. This lawn tractor is charging its battery at a rate of

15Amps constantly (Subject of the referenced post). Therefore I'm assuming that might be a relatively high load on the motor to run the generator at 15Amps. I believe 15A is the max the generator can provide since meter full scale is 18A. Then add to that, taking it out into a field and cutting field grass (wildflowers & grass, etc. abt 2 ft high) at the max recommended rpm, for an hour.

Upon turning off the engine, it went into a serious dieseling mode. It even spun backwards just before it finally quit for me (I finally pulled the choke to kill it). When I checked the oil it appeared there might have been some bubbles in it, which I think is a sign of over-heat. After cooling for a bit, checking the level showed it to be right on the mark, maybe a line width above it.

Do you think running with the battery generator maxed out like it was, on top of the cutting load and hot sun for an hour would account for it getting so hot? It wasn't literally that hot out; temp was around 78 F. The oil doesn't appear burned nor have any smell like it was, but ... thought I'd see what folks here thought. Oil was recently changed hours of use wise and still appeared clean.

Anything special I should do now?

Regards & TIA,

Twayne`

[Don Phillipson]

The maker of the alternator (generator) can tell you what its normal output should be.

Two-foot high grass and scrub would seriously overwork most machines sold as "lawn tractors," say the range 10 to 25 horse power. We may suppose it takes half the engine output just to move the mower through long grass (with the operator's weight atop all.)

[Van Chocstraw]

Engines are designed to operate at maximum horsepower without overheating. Maybe you have too much hay chaft in your cooling intake screen.

[Stormin Mormon]

Motors cool by sucking in air in the center of the flywheel, and forcing the air over the cylinder head. So, take the motor cover off, and scrub and clean the engine.

[Tony Hwang]

Hi, Don't know about motor over heating. Advancing timing too much can make engine run hotter. But if battery is fully charged it shouldn't charge any more. Maybe regulator is acting up? BTW, is it alternator or generator? They work differently.

[Hustlin' Hank]

ng field grass

ppeared clean.

I think you should trade it in and get a new mower. It has too many problems for you to deal with. Also, cut your grass more often. I'll give you $50 for it as is. :-)

Hank

[Twayne]

No humidity or dampness problems; screen, everything clean, fins clean, etc.. I always watch that in case of fire hazards around the engine. The flywheel is actuall pretty well designed and besides pulling air in also stays nice and clear.

Twayne`

[Twayne]

Alternator, unfortunately. Source is magnets on the motor's shaft inside the crankcase.

[Twayne]

Mmm, I don't THINK so! And if you want the full 5 acres cut more often, especially when I'm sick for a period of time, well, ... come on over & bring a 6-pack or three!

Twayne`

[stan]

15 amps at say 12 volts =3D 180 watts. 180 watts is about 180/750 =3D about one quarter of a horsepower. Even doubling that to half a horsepower does not sound like a motor overload. Is motor over-revving? Forced to work too hard?

[Hustlin' Hank]

I cut 4 acres, so 5 isn't that much more. Anyway, if you are ill and can't mow it often, you'd be better off hiring it doen when you are ill. Your mower isn't a bush-hog. It is made for residential service. That means cutting more often.

Hank

[Tony]

I always try to let my small engine equipment run at about 1/4 throttle for a minute or so before shutting it off. That allows the motor to cool down a bit so the little bit of carbon on the piston isn't still glowing red when you turn it off. Especially after cutting the high grass, it was most likely overheated and you could have caused permanant damage, but maybe not. Anyway, after using it really hard, let it run

1/4 throttle a couple minutes before shutting it off. (and also let it warm up a bit before putting a heavy load on it)

[Twayne]

lol! You sure know how to make an electrical engineer (retired) feel dumb! Why didn&#39;t I think of that? Don&#39;t answer that! < G >

The motor&#39;s not over-revving as measured by my calibrated earball anyway so if it is, it&#39;s not much. But it does sound loaded without the blades (or any other attachment even connected) running. I did find a spec online for my tractor that said the regulator output max was 15A. And someone else mentioned that if the rectifiers were shot, I&#39;m seeing current going in, then curring going out, so it might read high, but - I don&#39;t uderstand that since it&#39;s DC where I&#39;m measuring the voltage, which is schematically adjacent to the rectifiers. But it might explain 29V ac measurement.

I&#39;ve determined the regulator/rectifier is shot by comparing things to another working tractor with the same setup except it&#39;s a single cynlinder 17 HP. I tried to measure on into the stator but it&#39;s not possible without some real disassembly, so I&#39;m hoping just replacing the regulator/rectifier will do the job. $71 with $13 of that being S&H from Sears and $9 tax! What a ripoff! We&#39;re very rural here. The other tractor shows everything I expected to see on mine so it&#39;s at least verification that I&#39;m looking at SOME of the right things. Right now I&#39;m letting it set for a week until the part arrives, to see if the battery is recovered or shot. So far it seems to be holding its charge just fine.

Thanks,

Twayne

[Twayne]

Good advice. I -think- I always do that, but ... famous last words, you know?

Twayne`