Bronco spark, but no ignition / take off?

SnowHillMan

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Hello,

First time poster - I picked up a Troy-Bilt Bronco mower yesterday. The unit turns over (with the assistance of jumper cables - bad battery). However, it does not seem to fire/catch. I emptied/cleaned the gas tank, put in new gas, replaced the fuel lines (nasty/cracked), took the carb apart and cleaned the carburetor bowl (also nasty). I pulled the spark plug which looks fine and I can see spark when I grounded it against the engine and turned the motor over.

When I put it back together, it still does not fire on it's own like it's trying to start. Even hitting it with started fluid did not seem to get it to catch for a few seconds.

I am thinking I will replace the carb and fuel solenoid underneath it, since they are not that expensive and will give me piece of mind that they are clean/functioning.

However, I don't know that it will solve my problem since I didn't get a temporary heartbeat with starting fluid.

Any thoughts? Am I on the right track? Am I missing something? I'm not a rocket scientist, but the mower isn't a rocket either!?! The fact that I am not getting a hit with starting fluid has me a bit concerned.

Thanks in advance for any suggestions!
 

bertsmobile1

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Spray a short shot of starting fluid ( i like t use carb cleaner down the plug hole and with new plugs try again
If the engine fires and runs fine a second or so then stops but would not fire with starting fluid sprayed down th e carb throat then one or both valve are not working.
If you have a spark and it does not fire at least once with fuel down the plug hole then the timin is off .
 

SnowHillMan

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Thanks for the reply! I took the plug out, gave it a shot of starting fluid, put the plug back in, attached the plug wire, turned it over, but got no signs of life -- just the starter spinning the engine.

I took the plug back out and tested it again - ground it to the side of the engine. There is good spark. I have not set the timing on an engine before. How complicated or how much do you have to tear down to accomplish it? I don't have a lot of specialty tools.

This is an older (old), single cylinder engine. It's a Kohler model SV540S. Serial number is 3909302353. The Kohler tag indicates the build date was 4/3/2009. I'm not sure if I should try to revive it, look for a replacement engine or pass it on to someone else, notifying them of what I've come across so far. The rest of the mower, including the deck, seem to be in good shape -- nothing rusted out or scratched/dented. I've had my share of battle worn units that were run hard and put away wet, but this doesn't fit that description.

Thanks in advance for any thoughts.
 

bertsmobile1

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The timing is set by the flywheel which has a key in it which can shear
Next step is to remove the rocker cover, rotate the engine by hand and check that the valves are mving in & out .
 

SnowHillMan

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Okay, I took the cover off and was half expecting to find a loose rocker arm or some blown piece, but everything seemed to be well connected, with parts moving in and out as they should when I rotated the engine.
 

bertsmobile1

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OK so that only leaves the flywheel key broken and the engine is out of time or something horrid inside
Pull the blower housing off
Remve the nut / bolt that holes the flywheel and heve a very close look at the key waay slots
The on in the flywheel & the one in the crankshaft should de aligned and making a PERFECT square .
 

SnowHillMan

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Okay, I removed the nut to the flywheel and the key is still there in position. I actually removed the flywheel and things do not seem amiss there.

Thoughts on next step? Time to take the engine apart?
 

bertsmobile1

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Well that only leaves one or both of the cams being out of time with the piston movement
So yes time for the scuba gear and deep diving into the engine.
Nice thing about this one is you do not have to remove the engine from the mower, just slip both belts off
then take the top cover off the engine.
The stator wires will not pull through the cover but you leave it on the cover and just flip it out of the way
The cams are identical and the plastic gear have been known to break allowing the cam to get out of time
 

SnowHillMan

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Thanks for the insights and quick replies! I really do appreciate it! I wouldn't normally go this far into the engine, but at this point it is man against machine and I want to see it through to a successful repair. I am not sure I will get to the next step today, but I'll keep you/everyone posted.

I like to take lots of pictures when tearing down, which helps ensure I don't end up with extra parts by the time I get it all back together!?! These discussion boards and miscellaneous youtube videos really are lifelines to novice wrench turners like myself. My hat is off to you for sharing your expertise!
 

SnowHillMan

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I took the top cover off. A couple of the front bolts were already loose, which seems to be a common issue from some research I have done. Surprisingly, the inside did not look too bad. I did not notice any metal/plastic shavings at the bottom of the well and the cam gears appear to line up.

I attached a couple photos. I am not sure where the small (governor?) gear or the bushing go? How do they attach? They appeared to drop out when I lifted the cover off. Are they supposed to be snugly attached to something?

The compression release lever seemed to operate correctly with the spring attached.
 

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