# Another Briggs V-twin "popping" backfiring out of intake



## bigalby01 (Jan 12, 2013)

Hello everyone, hope all is well with every member here. Its been a while since ive posted but I hope to make up for lack of posting by making "quality" discussion posts. 

Here is my situation. A month ago I purchased a Cub Cadet LT1045 with a bad Kohler Courage single on it. I ended up buying a briggs v-twin 18.5 that needed head gaskets. I installed new gaskets, cleaned it up and installed it on the cub. Besides the exhaust it was easy with no issues. It turned out so well I gave it to my father for his birthday. 

So last week I stopped at an estate sale and found a cub cadet LTX1045 with a bad kohler courage twin engine. After the install (and custom exhaust work) I started it up and noticed a popping on low and high idle. I figured carb so I soaked, cleaned, soaked, picked, soaked and blew air through all ports. I changed a few gaskets and an o ring (its a nicki carb- 2 barrel ). Still she popped. When i unplug one spark plug the popping stops. I also sprayed carb cleaner on th intake gaskets and found 2 leaks so I changed the gaskets. Still pops. So I decided to change out the plugs (even though there new). still pops. i decided to swap out the coils from a known working engine I have. Still pops, so I adjusted the coils a little tighter then a little looser as well as the OHV valves. The rider starts easily and instantly, runs good with the popping one unplugged but its driving me mad. i next changed both heads with known working ones. I also installed new head gaskets. Still popping. I also tried all 3 carbs, still pops. On a long-shot I replaced the fuel pump and all lines or the fuel pump. still pops, then replaced flywheel key. Still pops. I readjusted valves again, measured there movement and compared to others & they were all the same. I did end up finding a white intake calve. I replaced valves with known working ones. I decided it was a valve seat slipping but after checking there solid. I then checked the valve springs, and valve guides. All are good. I pressure tested both and received 140 on the good and 120 on the bad. After running and getting warm both o them drop pressure down to half of the above numbers. I am out of ideas so I purchased another motor (briggs vtwin 20hp with plastic intake, all my intakes are metal). The problem is I am loosing sleep over this. I need answers. I even have a retired corvette engineer trying to figure it out. I also noticed when running and popping i notice a fog of fuel in the intake. I forgot to mention I checked and compared spark and found there both perfect. I also checked the cam and governor as well as other internal parts. All are great. 

ive seen this problem on a ton of sites on here an other places with no true fix. 
Any suggestions please respond. Possibly im over thinking this. Thank you everyone for looking and helping. 


the first pic is the last cub i converted to briggs v-twin
the rest are the one im stuck on now. the red engine is the one, you can see it taken apart as well.


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## Ed_GT5000 (Sep 30, 2003)

I don't have an answer for you but I can share my experience, I once bought a brand new tractor with a briggs intec v twin. It ran fine untill it got in high grass, under heavy loads it would get hot and would pop out the carb. It was such a problem I returned it.


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## bigalby01 (Jan 12, 2013)

Update 5/16/14

I end up tracking down the nice 20HP V-twin I mentioned in the above post. I change the head gaskets while I have it on the bench, and remove the popping twin. I then install the 20HP from a yellow alien looking MTD. I ran the engine 20 times prior to removing it. I installed it on my Cub, had to change the throttle cable and choke cable as well (thankfully a store Tractor Supply sells a choke and a throttle kit with over sized cables.) I button it up and fire it up and IT POPS!. Same head popping. Then it clicks, the only thing that is the same on BOTH motors is the freaking exhaust. (ill attach pics because everyone likes pics) We end up breaking the muffler welds and find a broken "baffle" inside the muffler floating around and one pipe was nearly bottomed out in the muffler. Im not sure if this is the case for any others who experience the popping but in my case it was. After a buddy welded up the muffler with his mig (thats his shop in the background) it ran perfect. We also fired up the old popping bad motor and it purrs as well with no popping. So I now have an extra v-twin that is mostly rebuilt. This was a team effort between myself, my bro in law and a close buddy. Heck of a learning curve

I learned alot on this one. Hopefully this will help others

enjoy the pics. The yellow rider had a bad trans and the 20hp engine. The rest of the pics are just "shop" shots.


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