190c riding mower runs like it is on one cylinder....

[mattbatson]

Ok,
so I have this mower since 2005 and it has been bullitproof...even after mowing a 5 acre homesite for several years.

(25hp V twin briggs and straton)

however, lately it started running rough.

First, it was doing the surging thing

Then, it started backfiring and you would have to choke it even when warm to start.

Then two weeks ago it just plain wouldnt start.

So, I thought carb rebuild.
Bought a carb rebuild kit and tore into it. First thing I noticed was how absolutely spotless it was inside the carb. Like brandy new spotless. I almost stopped and just put it back together cause I figured I would get it dirtier rebuilding it then just leaving it alone...
The emulsifier tube thingy was clean with all open holes. Jets looked brand new.
I replaced some of the stuff, but not every jet. It just didnt look like it needed it.

I then replaced the fuel pump and found the little vacuum line thing that plugs into the engine valve cover on one end and fuel pump on the other (enables the fuel pump to "pull" a vacuum) ...had a little split in it.
So after new pump and new vacuum line and partially rebuilt carb it will start, but not with the choke. If you choke it, it dies.
When it does get running, it runs like a v twin that is running on one cylinder and smokes a lot.

So I did some more reading and thought ignition module (spark plug wire is permanently connected to the module, so have to replace it as a whole unit). I have one coming in on friday.
Reason for one is that I figured both would probably not be bad at the same time, and it would not run at all if both were bad.

However, today I'm fooling around with it and find that both plugs have healthy looking sparks. I ohm'd both ignition modules by putting one lead on the one wire (black), that connects to the ignition module...and the other lead on the spark plug wire.....both had the same readout...and neither was infinite resistance.

did a compression test on engine and got over 120psi on both cylinders.

When I had the carb and manifold off I could see into the head and it looked as spotless as the carb.

I'm going to upload a video of it running in a minute....

 

[mattbatson]

 

[tcartwri]

pull the valve covers and look closely through the valve springs at the valve guides. Pull the pushrods and check for bends.

very common on these motors for the guides to move and hang one of the valves open when they get hot.

 

[mattbatson]

pull the valve covers and look closely through the valve springs at the valve guides. Pull the pushrods and check for bends.

very common on these motors for the guides to move and hang one of the valves open when they get hot.

will do that tomorrow and post up what I find...thx

 

[mattbatson]

finally got video up
looking under the valve covers now

Dd on Vimeo

 

[beenthere]

Normally the choke would kill the engine, so that doesn't surprise me.

But beyond that, not sure what to suggest looking at next. Don't like the smoke in the exhaust, but may be pointing to getting way too much fuel and not enough air.

Might need to do what tcartwri suggests next.

 

[Gator6x4]

You can start the engine that is good. Start the engine and with a pair of insulated plier or a plug wire removal tool pull the plug wires off the spark plugs one at a time. The cylinder not firing will not stall the engine, the cylinder firing will stall the engine. Using a OHM meter to check the plug wires only shows the wire is not bad, not whether the ignition module is bad. 120 PSI on both cylinder does not sound like the valve train is malfunctioning. I think you are going to find you have a bad ignition module.

Don't run the engine long with the shrouding off. It will run hot very quickly.

 

[mattbatson]

kind of crappy pictures...but it was at night

I cycled the engine and watched the valves and they seemed fine. Didnt seem bent, everything looked like it should...so far as I could tell.

 

[mattbatson]

You can start the engine that is good. Start the engine and with a pair of insulated plier or a plug wire removal tool pull the plug wires off the spark plugs one at a time. The cylinder not firing will not stall the engine, the cylinder firing will stall the engine. Using a OHM meter to check the plug wires only shows the wire is not bad, not whether the ignition module is bad. 120 PSI on both cylinder does not sound like the valve train is malfunctioning. I think you are going to find you have a bad ignition module.

Don't run the engine long with the shrouding off. It will run hot very quickly.

I will try the plug wire while running thing in the morning. I agree the valvetrain does seem to be okay...at least I really, really hope it is.

I will be getting the new ignition module on friday...but in meantime will see if I can narrow it down to which one.
I hope that is it.

thanks for all the advice

and all the reply's...great help on here as usual.

I will do my part, and post up afterwards with what fixed it.

thx

 

[mattbatson]

ignition module didnt fix the problem.

weird too, because I had pulled the plug wire on one side while running, and it ran the exact same...so I figured it was definitely the ignition module.

so now we are off to lowes to buy another john deere riding mower like what we have (54 inch cut) as we have four properties that have grass out of control...and I've been trying to fix this issue for three weeks (mostly waiting on parts)

now I have time to tinker, and will eventually pull the carb apart again, and this time do a complete rebuild...no matter how pristine and clean it looks inside