Engine runs ok until the blades are engaged, if I take the plug wire off the left side, it has no effect on the engine running.I changed plugs and checked the coil and wire, it has fire and compression. If I take the wire off the right side the engine dies. I did not check the carb, although the plug in the dead cyl shows some gas on it.

The wiring diagram shows safety circuit logic as; While brake OFF, operator must be in seat else kill engine. So I don't believe it's a safety circuit issue.

If it's not a safety circuit then most likely engine performance. The twin v cylinder engines can seemingly run ok on one cylinder until the load from the mower deck is applied and then they sputter and die.

To determine if this is the case, disconnect one spark plug wire and try to start. If it runs then reconnect the plug wire and disconnect the opposite cylinder plug wire. If it runs then it is firing on both cylinder and further troubleshooting is necessary.

If it fails to run with either plug wire removed then theres a dead cylinder, the cause of your issue.

whatever the pto is hooked to,is putting pressure on it and slowing it down,if its a deck,then the spindles are bad or binding,blades need to turn freely

blade brake is engaged unhook it and try turning the blade by hand should work

swap the coil with the other side and see if that plug gets sooty instead of the one that has been

If it has a B&S engine, and many do, try this. Remove one spark plug at a time and start the engine. If it runs with one plug, but not the other, then you have a dead cylinder. That is why it seems to run OK so long as no load is on it.

I have had 2 different mowers with B&S engines which bent the valve push rods on the left (as the driver sits) side of the engine causing the problem you speak of. And if you google this issue you will find that I am not the only person who ever had this scenario.

If you have the OHV type engine you can pull off the little valve cover, next to the spark plug, and see the rocker arms and the push rods behind them. Replacing them is about as easy as it looks, however setting the gap between the top of the valve and the rocker is best left to someone who knows what they are doing.

A common problem on the 21 & 23HP models is bent valve push rods on one cylinder. With this the engine runs and seems fine, albeit a bit quieter, until you put a load on it like engaging the blades which causes it to nearly die. So you may want to eliminate this as a possibility by running the engine with one plug wire removed and then the other. If it runs with one wire on alone, but not with the other wire on alone, then you have a nonworking cylinder even though it is receiving spark. Just a thought.

I had the same problem on a 21HP, you are running on one cylinder. Take off the valve cover and most likely you will have a/some bent valve push rod(s) which is common on B&S V2 engines. They are cheap to buy but kind of tricky to install and properly adjust.

If the engine runs ok when the blades are not
engaged then the engine is all right. Maybe its a faulty safety blade switch or a wire to the switch is stripped and is earthing to the body. Stephen

Try a new governor spring.

This is most likely a belt problem. Check the deck drive belt that runs from the mower deck to the engine it/s come loose and got stuck between the guides.