Dogbane cooked my 8199G

[daugen]

My last mowing job of the season was about half an acre of six foot overgrown weeds, affectionally called a "meadow" by the property owner.
Going along just fine, doing the last pass, but going through a thick patch of some large weed that created an enormous cloud of white fluffy material, so much
so that some blew across the road nearby and I bet folks wondered where the snow was coming from. I didn't think much of it, only an hour long job and my Gravely was perfect
going into this job. In a period of ten seconds, I smelled something funny, and then the motor quit like a light switch thrown. I got off the tractor and looked in the rear and just
did a real "oh no". Air intake 100 percent clogged with white stuff, inside of air cleaner clogged, and a pile of seeds off in the corner. Smoke pouring out of the engine but luckily nothing lit off.
What really worried me was looking down at my glass gas filter, and seeing the gasoline boiling merrily away. Not good. It turned over just fine, no strange noises, but no spark.
I think I cooked the coil or the condenser; at the shop now. I asked them to change the oil too, and check the fuel lines; got way too hot in there for my liking.

Since I figured I cooked the electronics, now was the time to install Kirk's electronic conversion kit I have had for more than a year, never getting to it.
Kirk Engines, Inc. >> Garden Tractor Performance Parts

Really hoping I didn't warp a head.
Probably a good time to take the head off and clean in there anyway.
Really annoyed me screwing up one of my favorite pieces of equipment. Just never thought it could happen that quickly. Live and learn.
and I hope I didn't breath too much of it...: Dogbane contains cymarin, a cardiogenic toxin that causes cardiac arrhythmia in humans
Thought it was milkweed, and maybe there was some of that in there too, but next year, I mow at least a month earlier to avoid this.

 

[Gary Fowler]

Sounds like you need to mow a couple times a year if it was 6 feet high. That is what we had when we bought our place and 6 feet high weeds were the low spots. It took a couple of years whacking it down 2-3 times per year to get some grass growing in place of the weeds but now the weeds are all gone except for some occassional thistles that blow in and we cut those by hand when we find them.
We would have to come home about every 30-45 minutes and blow out the radiator and that was running the FEL low to kind of knock over the weeds first.
Sounds like you need some kind of overheat kill switch installed on your mower.

 

[daugen]

Gary,
the lady whose property I mow likes to consider this weed infested patch her organic meadow....groan. At least she now realizes that we have to mow it earlier and more often.
Air cooled engine, maybe the fact it's an old fashioned solid iron K series will save it. Dealer promised me an answer this week.
I have another thread "repowering 8199G"....hope I didn't jinx myself! Drew

btw, haven't found anyone that makes a pyrometer for an air cooled; if I have a temp gauge, I'd pay attention to it...Always wanted one.

 

[RichardTX]

The Onan P224 on my 24G has an overheat sensor that is bolted to the right head. It has a Onan part number of 309-0559.


You can order from sears.com

Cost is $41

http://www.searspartsdirect.com/par...sessionid=tu4Lp-Y3-hqw1FijjkhWvw**.pdbot302p1

That switch was also used on some B43 and B48 engines.

 

[daugen]

an overheat sensor is a good start, and shows Onan had a commercial approach. But...if it's a sensor that trips a light, that's good, but not as good as a gauge, though if it shut down the engine,
that at least provided some protection.
Any idea at what heat limit it tripped? I'd be interested to know how hot they consider "too hot". Thanks.
and sorry, what's a B43 and B48 motor?

 

[RichardTX]

A gauge is going to cost you and then there is the ignore factor. Just because a gauge is there doesn't mean it gets looked at.

The sensor could do whatever you want. If you want a light and/or buzzer to come on, that is easy.

If you want it to kill the engine that is easy too. Just connect it to the engine kill wire. On Kohlers do not try to kill the engine and turn on a light at the same time. Many an ignition module has been fried that way. To do that requires a relay.

The Onan B43 and B48 were used on the Gravely 816T and 818T tractors. One engine was 43 cu in displacement and the other 48 cu in.

I have no idea what the temperature trip point is. Whatever it is, it is right.

 

[daugen]

the culprit was found, my coil became a large thermal fuse, melted, shorted out I suppose, or just failed, and off went the engine. Since I supplied the shop with a replacement coil, the bill wasn't too bad. New fuel line from fuel filter back, and had to tighten 8 of the 16 head bolts. Hmmm. Guess that sucker expanded a bit. That tells me they didn't take the heads off, which I wish they had, but it runs just fine. And starts quickly.
I'm going to fashion an open weave furnace filter to fit in behind the stock bumper guard and the intake fan. That might help. And a little more attention paid by the operator.

 

[daugen]

I'll take a pic of the new coil installed later today. It's bright yellow and sticks out like a sore thumb. The new Bosch coil I have on my Cub Cadet 125 is an attractive metallic blue, this thing is dayglo yellow.
I have plenty of Gravely paint...and I need to inspect the engine closely to see what paint I burned off anyway. All the shrouding was taken off and everything inside cleaned out. So I'm back in operation; I really missed the thing
because it has a ball hitch on the back and I don't have one yet on the Kubota tractor.

I think the governor is getting very tired. Hunts and rolls a fair amount at idle and is set too low now, it will stall when cold. I have a digital tach on it, what should the low and high rpm settings be? My understanding is full throttle/WOT should produce 3300 under no load/light load, but I'm now only getting 3200. I never liked to run at full speed, no need really, but now while mowing, I push it all the way up, and it was running in the 3150 to 3200 rpm range. I use to have 100 more rpm and I think I want it back... The low speed hunting can be eliminated mostly by a little higher idle speed, which I will do next. The governor renewal is what I will research next.

I've put 180 hours on the Gravely in the three years I've owned it. Some of that is high load, high heat operation, doing field mowing. But the hour meter is still under 800, so that helps. All those loose head bolts concern me, and why if they were loose weren't the heads taken off and new gaskets reflected in the parts list? I thought this was a good time to do that, but apparently my overheating period was short enough that I didn't damage anything more than the ignition parts. Fine with me.

I was considering putting three rib front tires on the Gravely, to give me better side traction on slopes when mowing. I use the Gravely to mow those areas I won't take the larger tractor and finish mower. Has anyone you know installed these? Wondering if it would leave tracks on damp lawns. Unit is mostly used off the lawn so those front turf tires aren't all that hot on hills. I grew up with tri-ribs on a JD B, and they rarely lost grip from my memory.

 

[daugen]

Richard,
you are a remarkable resource of info, thank you.
I found when doing heavy field mowing that last hundred rpms helped, just seemed to not bog as much; clearly I was taking all the hp out of the engine. Only time I have to use full throttle, normally I like to keep it much slower, and when doing the occasional normal grass mowing with it, probably run in the 3100-3200 range, or whatever the little digital tach thinks I'm running. But it always has fresh Rotella 30W in it which I watch like a hawk. Burns, drips very little oil, more dripping. I think the seal between the engine and trans is unhappy, and someday I will have to split it all and will do a serious redo then. For now I'll hike up the idle and check the air mix. It backfired on me with a big pop, so that sounds like things are a little lean as you suggested. It was just tuned up, with carb adjust, when I overheated it, and now with the new hybrid electronics on it, maybe it needs some fine tuning again.

Still finding little bits of the cottony material on the mower.

 

[RichardTX]

I have a friend that has a 18G and he has adjusted his so that the engine spins at 3600 RPM. He swears by the added RPM and power. When I had a M18 I ran it at 3600 RPM. The added RPM does help.

I have since upgraded my G series tractor and replaced the Kohler Magnum 18 with a 24hp Onan. That turned out so well that I replaced all of the Kohler engines on my 4 wheel tractors with Onan engines.

Popping thru the exhaust on shutdown in almost normal on those Kohler twin engines. To help stop that from occurring, let the tractor idle for a minute and then shut it down. It may not stop it but it should be less frequent.

 

[daugen]

initial diagnosis was water in the gas. Never had that as an issue before on this Gravely. I had the dealer drain and flush the gas, we shall see.
and I put a new set of NGK UR4 plat plugs in, something nice for the holidays...
Will pick up on Monday.

 

[daugen]

Popping thru the exhaust on shutdown in almost normal on those Kohler twin engines. To help stop that from occurring, let the tractor idle for a minute and then shut it down. It may not stop it but it should be less frequent.

an update. Now little popping when shutting down, but a huge bang when I start the warm engine without using the choke. Am I running too lean? Otherwise it runs fine.

 

[RichardTX]

Sounds normal to me. Best way to prevent it is to let it idle for a minute or three after running it hard.

 

[daugen]

Richard,
normal can't be letting off a bang that can be heard a mile away.
And almost every time I start it when warm. When cold, using the choke, no problem.
I'm going to do the obvious things like check the plugs (nice plat NGK...) due to the
electronic ignition conversion kit I put on, make sure nothing looks strange there, but if the plugs
are clean, which frankly I'd expect if it were running lean, then what else could it be other than a carb
adjust?

I understand the popping when stopping. It's the bang when starting, and I'm talking a seriously loud bang, not some little pop, that concerns me. Have to wonder what all that is doing to the valves, etc.
Since I can eliminate it by pulling out the choke some, I still think I should do a carb adjust. Can't hurt....

 

[RichardTX]

If you really want to solve the problem, shut off the fuel at the tank and let it idle until it runs out of fuel. It is a little extreme but it works.

What happens is that when you shut the ignition, the engine continues to spin sucking fuel out of the carb, throught the cylinder and out the exhaust. air creeps in from the tail pipe, hits the hot fuel mix in the muffler and BANG! There are other scenarios that also result in a muffler explosion. Have you ever noticed the lack of a bang if you stall out the engine?

You could try putting a longer tailpipe on it. That will permit the fuel in the muffler to cool below the flash point before air gets in. I have had delayed bangs. Shut off the tractor, get about 10 ft away and then it goes BANG!

A leak in the exhaust system can also cause a backfire. Let air in at the header where it bolts to the engine and that can cause a big bang at shudown. You might try replacing the exhaust manifold gaskets. When I remove exhaust bolts, I replace them with stainless SHCS. A little high temp Sevr-Seez helps keep the threads from galling.