Briggs 22HP els motor backfiring loosing power I am stumped.

dirtyb115 · May 8, 2017

Hello all. I am stumped trying to figure out what is going on with my zero turn. Its a 2006 Dixon ram 50, it has a 22HP els Briggs motor. Up until Saturday i have had zero problems with it. This past Saturday I was mowing some overgrown grass and it started to back fire and lose power especially going up hill. It progressively got worse by the time i had finished mowing. First i replaced the fuel filter, no change. Then i changed out the plugs, no change. Next checked the valve clearances, They were all around .006. I adjusted them to spec, but still no change. Then i pulled the push rods, none were bent. Went through the carb and everything seemed okay. Did a compression check and one cylinder came in around 100, the other 110. Tried unplugging wire on each cylinder when running and each time motor would run noticeably worse. Not sure what to try next. Starts great, idles great and runs pretty good until under load. The exhaust seems a little louder to me, but not positive on that.
Anyone have any ideas?
Thanks!

rustydollar · May 8, 2017

Possibly a blown head gasket.

dirtyb115 · May 8, 2017

rustydollar said:
Possibly a blown head gasket.

Wouldn't the compression check catch that?

rustydollar · May 8, 2017

dirtyb115 said:
Wouldn't the compression check catch that?

My old eyes missed mention of the compression test, thanks for the heads up.

tomplum · May 10, 2017

Easy check- remove the flywheel nut and verify that the key is not partially sheared. You may need to check a couple of additional things under the valve covers. 1) look at all 4 valve guides and note if they are protruding from the head about the same distance or has one started to migrate. 2) Remove the spark plugs and roll the engine by hand. Compare the valve lift as you do, once again - they should be close to the same. Should you have a worn cam lobe, you'll know.

bcp · May 10, 2017

tomplum said:
Easy check- remove the flywheel nut and verify that the key is not partially sheared.

I've had the key offset over half its width after an impact.

Bruce

dirtyb115 · May 10, 2017

tomplum said:
Easy check- remove the flywheel nut and verify that the key is not partially sheared. You may need to check a couple of additional things under the valve covers. 1) look at all 4 valve guides and note if they are protruding from the head about the same distance or has one started to migrate. 2) Remove the spark plugs and roll the engine by hand. Compare the valve lift as you do, once again - they should be close to the same. Should you have a worn cam lobe, you'll know.

Thanks for the reply. I forgot to mention in the first post that I also checked the flywheel key, it was fine. I also tried unhooking the kill wires and no difference and even cleaned out the muffler. I will take a look at the valve guides and and look at lift as well hopefully tomorrow. I went through the carb again today hoping i missed something but still doing the same thing.

dirtyb115 · May 11, 2017

tomplum said:
2) Remove the spark plugs and roll the engine by hand. Compare the valve lift as you do, once again - they should be close to the same. Should you have a worn cam lobe, you'll know.

Well, i think the mystery is solved. The exhaust valve on one of the cylinders is barely moving. Guess its time for a new camshaft. Not looking forward to pulling the motor out. Anyone have any tips on replacing one of these? I saw one video but they recommended having an oxy torch to get the bottom pulley off which i dont have. Hopefully pb blaster will work.

tomplum · May 11, 2017

Are you to the point of removing the engine? Hopefully your drive pulley comes off more easily than heating. Many of them do. MTD products of the last 10 years or so are buggers. Dixons, I dunno. If it comes to the point of using extraordinary measures on the pulley, do your homework on price and availability of a new pulley. PB isn't a slouch, but order a can of Kroil if you want great stuff.