Engine Problem Briggs 12hp

[KB9LOR 4]

Hello everyone! Just got my first "Horse" this past weekend and yeah I know pics! will get them up tomorrow but here is my predicament, I have a 1989 WH Model 212-H with a Briggs 12hp model # B-281707, here is the problem that just started, when I go to engage mower the engine will die, now when I go to restart the mower it will backfire, let it sit a couple mins, it will fire right back up engage mower, everything fine right? nope when I go to moving the engine will just lose power and die, now if I do not run the mower it will run like no other, here is what I have done so far:

1) Mower is free, you can spin the blades

2) Changed plug

The manual says it could be the carburetor is in need of adjustment, I don't know. I do know this started all of a sudden, I mowed last weekend with no problems, any ideas?

Thanks in advance!

Brian

[VinsRJ 721]

Hello,

Start with the carb. Give it a complete cleaning, inside and out. Might not even be a bad idea to get a kit for it too. Dirt may have clogged up an air passage and/or choking a fuel passage.

Next check the inginition. A weak spark can keep an engine running but when sever load is placed on the unit (like at intial deck engagement) there is just not enough juice. Points, condensor........ You get the idea.

The backfire you stated is to due the motor being shut down by the mower. The last unburned air fuel mixture is being pushed into the exhaust and firing upon start up right after shut down. If you wait a few minutes before restarting it shouldn't backfire. It maybe a sign of a rich condition but start with the carb.

The motor doesn't smoke while running correct?

[KB9LOR 4]

Corrrect, the engine does not smoke while running, wasn't sure why it was backfiring on re-start, going to tear into that carb today will let you know how it turns out, not new to small engines just been many years since I have tore them down and worked on them. thanks for your help it is much appreciated.

Thanks,

Brian

[KB9LOR 4]

Carburetor was not the problem, the Ignition is okay, went ahead and did a compression check should be 90 to 120 with 4 rev of engine, was barely 60 with 8 revs, so may have a ring problem, or could be a valve problem, in the process of a tear down, will update when exact cause uncovered.

Brian

[bitten 133]

Brian good luck and :scratchead:

[KB9LOR 4]

Thanks bitten, I am gonna need it been many years since I tore into one of these, but i am sure it will all come back to me, I hope!

And thanks for the welcome!

Brian

[KB9LOR 4]

Okay everyone who is interested, got the engine torn down, did a bore measurement, and from side to side horzontially it is less than .002 and the opposite vertically, it is .003 still close enough, it could be less as my hands are not as steady as they used to be. Checked valves they are okay, wrist pin, crank bearing okay, seems everything inside is good except for the rings, so got everything ordered rings will be in next tuesday, so by tuesday evening should be back together, and ready to work.

Brian

[Sparky-(Admin) 19,546]

Good luck Brian and keep us posted.

Mike........

[Docwheelhorse 2,560]

You will never get an accurate compression reading off of a Briggs due to the compression release built into the profile of the cam.... The only way to properly get a semi accurate compression reading is to spin the engine BACKWARDS. 60 Lbs with the engine spinning corectly was a good reading. When the engine fires up it is spinning to fast to utilize the compression release and the compression comes up to 100---120. I would have looked into the carb as it sounds like it was gaging when the deck was engaged...

Tony

[KB9LOR 4]

Tony, The Carb had been gone through and was doing the same thing as before the Carb rebuild, so went ahead and tore it down, too late to quit now lol! I guess a new set of bearings and rings wont hurt being she is 20 years old she should last me that long at least.

Brian