Briggs 23Hp Model 44L777 V-Twin Bent Push Rods

[Bertrrr]

If it will run on one cylinder at a time , do that and see which one is causing the backfire , back fire at the muffler indicates unburnt fuel hitting the hot exhaust, through the carb would indicate an intake valve not sealing in my opinion , you said you installed new valves - did you use lapping compound and lap them in ? This is a must

 

[TiIngot]

If it will run on one cylinder at a time , do that and see which one is causing the backfire , back fire at the muffler indicates unburnt fuel hitting the hot exhaust, through the carb would indicate an intake valve not sealing in my opinion , you said you installed new valves - did you use lapping compound and lap them in ? This is a must

The valves were installed in the new Briggs head with the springs and keepers as an assembly when I received the head. I did not lap them. All I did was install the rocker arms and set the new push rod gaps to .005 after installing the new head. I just did a compression test and both cylinders are around 150psi.

 

[Bertrrr]

Sounds like the valves are set right and compression verifies it. This back fire happens after it dies or you shut it down or does it just start running bad and backfiring all of a sudden ? It's possible the flywheel key got sheered and threw off your ignition timing , never saw one run with even a slightly sheered key but you never know.
This may be totally unrelated to your original problem as well ,
Backfiring through the muffer indicates unburnt fuel in my opinion .

 

[TiIngot]

Sounds like the valves are set right and compression verifies it. This back fire happens after it dies or you shut it down or does it just start running bad and backfiring all of a sudden ? It's possible the flywheel key got sheered and threw off your ignition timing , never saw one run with even a slightly sheered key but you never know.
This may be totally unrelated to your original problem as well ,
Backfiring through the muffer indicates unburnt fuel in my opinion .

Thank you for the reply. The plot thickens. It backfires intermittently when running and appears to be the cylinder with the new head. The other cylinder never appeared to have a problem. Remember I received this tractor running but I have no history. A wire going to the brake safety interlock was pinched under the battery so the mower shut off then the PTO was turned on. Engine appeared to run find after I found the pinched wire. When I received it I did not know it was only running on one cylinder, cleaned it and put it in storage.

I rechecked the valve clearance and they are correct. The new cylinder head had the valve and valve springs pre installed so I did not lap the valves? Should I have done so? My You Tube research takes me to three possibilities.

First, a burnt exhaust valve. It is a new head and valves and has only run maybe five minutes, one minute at a time during trouble shooting. Too soon to burn a valve?

Second, is the cylinder running lean? I have never worked on a two cylinder before. Can one cylinder run lean but not the other? The exhaust pipe very quickly turned red!! I have just removed the carb and getting ready to clean it. Note, when I got the tractor I could tell the carb was removed before because the choke linkage was installed incorrectly.

Three, the timing is off because the key may have been moved slightly. Have not addressed this yet, only put penetrating oil on the fly wheel bolt at this time.

Looking for the needle in the haystack!!

 

[StarTech]

Just worked a v-twin recently where the previous so tech put on the wrong carburetor where the jets were .05 mm each too small. IT cause the engine to destroy #2 cylinder head.

I had to rework the carburetor the engine would even off choke. Then I found the bad cylinder head with half of one push down in the crankcase.

 

[Bertrrr]

Being your compression was good on both cylinders, I'd say your valves are ok without being lapped in, When you get the flywheel nut off you should be able to see the keyway / key profile, I've never run across one even slightly sheered and have it run but never say never in this game. You may have mentioned earlier but are both plugs gapped the same ? Just throwing stuff at the wall now but worth a shot at different or new plugs

 

[Tiger Small Engine]

Being your compression was good on both cylinders, I'd say your valves are ok without being lapped in, When you get the flywheel nut off you should be able to see the keyway / key profile, I've never run across one even slightly sheered and have it run but never say never in this game. You may have mentioned earlier but are both plugs gapped the same ? Just throwing stuff at the wall now but worth a shot at different or new plugs

If the muffler is glowing, there is your red alert, literally. Go through carburetor and clean thoroughly. Make sure you have good gaskets and no air leaks. That is a good start and then see how it runs.

 

[TiIngot]

If the muffler is glowing, there is your red alert, literally. Go through carburetor and clean thoroughly. Make sure you have good gaskets and no air leaks. That is a good start and then see how it runs.

Thanks to everyone posting suggestions. I removed, disassemble and cleaned the carb including using torch tip wires in all the tiny ports. Internally, the carb showed absolutely no dirt at all. One of the cleanest one I have seem.

Have not installed it yet. Giving the task a couple days off to think about my next course of action.

Will post results later.

 

[TiIngot]

SUCCESS!! I owe everyone who replied a big thank you!! After pondering the issue for two days I pulled the flywheel. The key was sheared!! $2.18 later and it purrs. This has been a journey. I purchased this Snapper LT125 (2014) with 23.5HP from a scrapper for $25.00 last fall. It is the first V-Twin I have worked on. The following is what I went through:
1. Both cylinder heads were ENTIRELY clogged with mice nests. Never saw one this bad.
2. Purchased a battery. Found wire under the battery and moved it out when putting in new one.
3. Engine hard to start. Used starting fluid. Found carburetor installed wrong. The throttle/choke linkage was in the incorrect hole and the governor linkage installed wrong.
4. #2 Cylinder head had three stripped bolts on the valve cover. Some dummy used a power tool on it. Was able to salvage two of the bolt holes and use a bolt and nut on the forth. Set the valve clearance on #2 cylinder and new valve gasket.
5. Engine started up and appeared to run fine (I did not know it was running on one cylinder), except it died then brake pedal released.
6. Found wire going to the brake safety interlock, at one point was left under the battery pinching off the circuit inside the rubber insulation. Cut section of wire out and spliced in a piece. Tractor running and stored for winter.
7. Spring, used tractor twice and it started running horrible. No time to work on it so back into storage.
8. October, both cylinders getting spark but #1 valve cover was colder than #2. Found both pushrods inside #1 valve cover bent and broken. Installed new cylinder head and pushrods and set the valves on #1 cylinder.
9. Engine started but backfired through #1 exhaust. Re-set valves again. New plugs and it backfired less but exhaust pipe glowing red.
10. Removed the carburetor, disassembled it and cleaned everything using brake cleaner and torch tip wire. The insides were all clean but I cleaned it anyway.
11. Pulled flywheel and found key sheared and flywheel shifted 1/8". Reinstalled the carb, put in a new key and the engine purrs.

Again to all.....................THANK YOU