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Brief history. 2004 Troy-bilt Super Bronco Kohler Courage 19 Engine. VERY well taken care of, but still had my share of issues. I've always been fairly capable, well read and methodical in all I do but I'm not an expert. Worked out good for me so far.
2 seasons ago - Rebuilt transaxle (not the diff) just the innards, seals and bearings.
This season, oil leak from head gasket, top case (4 screws backed themselves out, one hitting the flywheel - a well known issues) and valve cover. No case damage. So I dismantled, cleaned / soaked (shiny head and valves - like brand new) rebuilt (put in a brand new carb - didn't bother cleaning & servicing). Full serving kit. First turn of the key she ran like new.

The past two time she was hard to start and keep running. Once warmed up it was fine, so I was figuring a carb adjustment might be needed. Though at idle the engine started hunting too.

Now for the problem.
This evening, I could not get it started. Lots of cranking, adjusting choke and throttle positions, nothing. Check spark plug, fuel lines, all seemed good. Finally though to give it a shot of carb cleaner and got it to sputter to a start (barely) while adjusting the throttle. Lots of stalls, but multiple restarts and about a minute I got it running steady but noticed the ammeter pegged, then it cut out - 20amp fuse popped.
Replaced fuse, got it started (difficult again) but while messing with the throttle again, noticed the ammeter current draw decreased with engine speed (Low engine speed still had a higher draw than I'm used to - but I was cranking the starter motor A LOT so I thought the battery could be weak).
While running full speed I saw one of my nice LED headlight cut out and start to smoke. I wasn't checking voltage during all this but I surmise it got way too many volts - I mean that's what fries LED bulbs.
I disconnected by headlights to take them out of the equation and let it run a bit, still high amps and in about 2 minutes it popped again.

Winched it back up into the shed & joined this forum.

I guess few key takeaways here are:
I did remove (carefully) and upper engine - including the coil and transformer. (Carefully and retighten everything with torque wrench to spec)
It has run fine a dozen times since rebuild
Odd high current draw related to engine speed
(Probable) higher than expected voltage on the 12v DC side.

Hope someone was willing to read my story and might have some input where to go next...

Thanks all.
Dan

First thing to do is to the output voltage of the voltage regulator. These on Kohler engines tend to go bad at anytime. Most usually just quit completely but it is possible for to fail in such a way that unregulated voltage is pass to mower.

Post the engines model and spec numbers and I’ll find you a service manual.

Model is a SV590. Thanks for offering, I actually have the service manual and just noticed the very good section on testing the electrical. I will pursue that later today or tomorrow. I'm assuming its the Rectifier-Regulator without testing, so I already ordered a new one & a 20A blade type circuit breaker. I can only assume the excessive cranking damaged it. I'll post a follow-up with what I find.

Then I still need to why starting has become impossible and why it began surging at low speeds. I'll probably check the valve lashing and maybe service the old Walbro carb & put it back in. (replacement was a Chinese brand one)

Two things come to mind with hard starting on those engines. First the choke is not closing fully for starting. Second float level is too low, resulting in a lean misturdy when starting.

Thanks. Choke is closing, had the filter box off while troubleshooting. New carb came pre-adjusted and worked fine for most of the season but that's on my to-check list once I solve the electrical gremlin.

Hey y'all, I'm back with an update - and looking for more help.

It shouldn't be this complicated...

1) New Regulator-Rectifier in
2) Valve Lashing checked - they has a little too much gap, fixed.

Same problem with starting - couldn't get it to turn over.
Took out Cheap-China-Crap-Carb, put back in cleaned and serviced Walbro.
She fired right up. Lesson Learned, and I should have known better.

BUT I still have the same problem - Dangerous High current draw and higher voltage at the headlights (i.e. 12V DC bus).
Voltage at headlight connector.
Engine not running - 12V
Engine Idle - 14.2V
Engine full speed - 15.8V

If I let it run full speed for more than a minute fuse would blow.

One other tested observation - while engine running, I disconnected the battery and the engine died (also had a lot or arcing while taking it off - proving high current draw).
1) This is NOT normal, right? A car can run without its battery. I assume the principals are the same.
2) Could this mean the 'alternator' (coil) is actually the problem? (I mean, what else could it be?)
3) Clarify for me, the transformer is still good since its providing the spark, right?

Please post the model and serial numbers for the tractor. I want to find a wiring diagram, as something does not make sense to me.

If you have a an anti backfire solenoid when you disconnect the battery it may be shutting off the solenoid killing the engine. Have you tested the AC voltage output of the alternator? Have you replaced the battery? Bad battery can cause high current draw. When you say transformer are you refering to the alternator stator coil or the ignition coil?

Failed voltage regulator. From service manual.

Disregard the battery part as that is if you had a bad battery which it sounds like yours is holding a charge.

BTW many newer cars will not run with the battery disconnected any more as it is now part of the voltage regulation system. Older cars can as they had a different system. It just as if the alternator is completely shut down. It is same with Kawasaki engines where when the battery is no present the voltage regulator shuts down completely.

Troy Bilt Super Bronco (2005) - 13AX60TG766. Will have to

The carb has a solenoid but no backfire specific one i know of - a) both from having my hands in every area of the mower and b) if I dont throttle down and wait 2 seconds before shutting off, it backfires something fierce.

I JUST put a brand new regulator in. I mean it CANT be that, can it? I'm gonna test the voltage off the alternator next. Can a bad alternator burn out a bran new regulator?

Clarification - Normal 12V DC at the Lights = Battery voltage as measured at the battery (seems obvious statement but want to be sure)
While engine is running, battery voltage AT THE BATTERY (i.e. charging the battery) is less than 14.7... it was 14.2V-14.6V

The voltage at the headlight was 15.8V at full throttle.

Thanks again

Hammermechanicman said:

If you have a an anti backfire solenoid when you disconnect the battery it may be shutting off the solenoid killing the engine. Have you tested the AC voltage output of the alternator? Have you replaced the battery? Bad battery can cause high current draw. When you say transformer are you refering to the alternator stator coil or the ignition coil?

Click to expand...

Transformer = The part with the wire leading to the spark plug. So I’d say the ignition coil. I assume that is an isolated circuit just for to fire the spark plug.

Its a new battery from the beginning of the season.
Just to clarify, I had no electrical issues until I had this hard starting issue, which caused me to do a lot of cranking. (But always cautious not to over crank for too long). Starter motor is still nice and strong.
As I said in my other post, I’ll check the ac volts later today.

thanks again.

Okay what the voltage output at the regulator during these tests as the voltage at the headlight should be the same as the battery. May have a faulty connection causing a large voltage drop between hte voltage regulator and the battery since it is lower than at the light.

Ok. Stumped other than the fact I received a new, bad rectifier-regulator, which still seems highly unlikely but not sure what else there is.

From the service manual..
1 Test - battery charging for no battery charge (skipped). There's definitely charge happening
2) Remove R-R connector, test voltage @ 3600RPM. Voltage ~38VAC at Idle, ~50VAC @3600. Good I Think. Specs say > 28VAC
3) Check stator resistance - 0.0 ohms - not open, good
4) Check each stator lead to ground - not shorted, good.

From the next section in the service manual - "test charging system for battery continuously charging at high rate"
Like @StarTech posted from the manual, Checking B+ to ground at 3600RPM I'm getting 15.8V, which is bad.

I traced all the wires and studied the wiring diagram. There are a number of safety switches and the obvious ignition switch (and backup PTO lockout override button) but nothing seems related. The B+ terminal feed back to the battery is quite simple and direct.

I guess I could leave the R-R disconnected and trickle charge the battery after each use, not sure how much battery draw there will be.

hmm.

StarTech said:

Okay what the voltage output at the regulator during these tests as the voltage at the headlight should be the same as the battery. May have a faulty connection causing a large voltage drop between hte voltage regulator and the battery since it is lower than at the light.

Click to expand...

Vout at B+ to ground is the same as the voltage at the headlights.

Vout at B+ to ground is NOT the same voltage as it is across the battery terminals (14.4ish vs 15.8) . (probably some load loss? / overcharging)

Closing out this post. It was the battery, though logically it shouldn't be since it cranks strong, has 12.2v without load and was trickle charged for days before installing. However i guess its a case of Occam's razor. I should have tried a different battery before heading down the rabbit hole.
I didn't put the old Rectifier-Regulator back in, but I suspect its fine.

Thanks everyone.