I have a 25HP Riding mower. I noticed the last time I used it, it started making a popping noise through the exhaust at the higher speeds. When it idles it seems to be fine.I replaced the fuel filter and cleaned the plugs and filter. Any ideas before I start digging into it.

you have a unseated valve you need a valve job about a 100.00 dollars

You might have more than one problem but I think I can tell you why it cranks slowly and draws so much current. Some of those cadets (like those with the Kohler Command 20) have a compression release mechanism on the cam which is intended to make that big engine crank easier. It disengages once the engine fires up via a centrifugal release on the (plastic) cam gear.If this part breaks, the compression release does not work, resulting in a lot of strain on the starter motor. Interesting design, bad materials. Sometimes the engine will start anyway but this is not a good idea to operate this way. Pull the valve cover. Look at the motion of the exhaust valve when you turn the engine by hand. It will look similar to the motion of the intake valve if this part is broken. If it's working correctly, you should see the exhaust valve open slightly just after the intake valve closes. I'll attach a video to show what it looks like. Replacing the bad part is a bit of work but not terrible.

I'd be tempted to shield the spring from the heat of the exhaust - is there any way to pop rivet on a piece of aluminium sheet and bend it to not impede the operation of the clutch?

sounds like the needle valve inside the carb has failed dumping gas into the crankcase and into the cylinder this overfills the oil and dumps it change the valve and seat change the oil a couple times add a fuel line shut off and run the carb out of gas when your done using it the newer fuel we get melts the rubber seal

check the safety switches

the blades and the trans use 2 different belts also is it a automatic drive and the release lever that you pull out to push it?

Hello. Thanks for using fixya. First thing i would do is make sure it has gas in the fuel tank. If that's ok. I would replace the spark plugs next. Could be that they are fouled out causing the no start problem.

with mine i checked to make sure there was no built up grass in the blade area and around the pulleys and wheels i would also check the tire pressure and brakes to make sure there not binding up.

The arm that engages the cutting blade tends to wiggle. Make sure it is pulled toward you (unengaged) before trying to start.