OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines 12.5 HP Briggs and Stratton

Hello Gurus,
I just done in the B+S motor on my ride-on Stihl Viking.
Have not taken it apart, but petrol is disappearing fast and it appears it goes into the sump, as the "engine oil" is very light. I hazard to guess, I have done in the rings.
Not a big problem, other then the ride-on is needed to keep the grass down in my caravan park.
Time is of the essence, therefore I am thinking of replacing the motor with a new one.
Your opinion is sought in "which motor" is suitable to replace a 12.5 HP, Synchro-Balanced Briggs and Stratton, year model probably (as per ride-on mower) 1996, so the motor has not done a bad job, if it's original.
I would need at least the same HP or bigger.
Thanks for your help and advise.
Frank

i had a sim prob with fuel in the oil it was that the fuel got left on and went thru the carby a new kit will fix this it only does it when its not in use so untill i have fitted the carby rebuild kit i simply turn the fuel off when ive finished.... when its running its fine

The problem you describe is definately within the carburettor, much simpler job than the rings, you need a kit for it which will include floatneedle seat and the needle itself, this should resolve your problem.

Thanks Gurus,
Great advise, I was going to spend $800.00 plus.
I am about to order the carby kit.
Thanks again Mikle and Joe and best regards to all.
Frank

Hi gurus,
Next time I will read my replies properly, Mikle :-)

I have been trying to find a carby kit for the 12.5 HP B+S, it has the following numbers on the motor.
Model Number: 289707
Type: 0114-22
Code: 96020728

Cannot find a kit for that model. Can anyone advise

Best regards
Frank

Frank, you need to clean out the fuel tank, filter if it has one, and fuel line. The problem is in the float bowl so you don't really need a full kit, but you do need the correct needle and seat. Replacing the seat requires a special screw which is difficult to get. Of course many people do a full carburetor clean-out once they work on it at all, and for that you would need the full kit.

If you post a picture of your carburetor we can establish which type it is, and give you some help with the float bowl overhaul if you wish. If you have the most common type of 12.5 hp carburetor in use about 20 years ago, you can read about the process in this thread:
https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showflat&Number=15306
However there are other types of carburetor that have been fitted to 12.5 hp engines, so it would be best to post a picture of it.

Hi Grumpy,
Thanks for your advise.
The carby is a Walbro 5-4993 LMT: those are the letters/numbers on the Alu case.
Sorry about the quality of the pics, I would never get a job as a photographer.:-)
I will clean the fuel system and the crank case and then put it al together again. If it works, great. If not, I;ll just have to do more work.
In any case, I will get whatever parts you recommend, Grumpy.
Again, thanks to all gurus and best regards
Frank

Hi all,
Lets not worry too much about the pics :-)
I'll go back to school next week.

Regards
Frank

I don't know that carburetor type, nomad, but I've attached a line diagram of it, with a crude circle around the needle and seat.



The hollow, roughly toroidal object to the left of the needle and seat is the float. I'm told this type of float seldom deteriorates, but inspect it for damage and shake it to see if it has fuel inside it. Your problem is probably just dirt in the fuel intake pipe and getting in between the needle and seat. Before you dismantle the carburetor, turn it upside down, suck on the fuel feed pipe (emptying the fuel out first, or preparing yourself emotionally for a mouthful of petrol), put your tongue on the feed pipe, and see how long it holds vacuum. If it doesn't hold it for at least a few seconds, you need to dismantle the float bowl, remove and inspect the float, remove and inspect the needle, and clean it and the intake pipe/seat area. Be gentle, the seat is delicate. Reassemble and see if it then holds vacuum. If it still doesn't, you need either to lap or replace the seat. If it is a metal seat (some are plastic) try lapping it first, its cheaper and easier. You use something like the lead out of a black pencil as the lap, perhaps putting some extremely fine lapping compound on it, and rotate it in the open end of the seat, where the needle normally goes, with something like an electric drill. Hold it straight, of course, or you'll make things worse than they were in the first place. Don't put any lapping compound on it until you've tried it without, first (graphite is abrasive, and pencil lead is a mixture of graphite and clay). Only lap it with a very light pressure and only for a very few seconds. Inspect the seat area where the needle touches it with a magnifying glass: you want to see an even, extremely narrow seating surface all the way around the seat.

Try the vacuum test again. If it still won't hold vacuum, you need a new needle and seat. We'll need more information on your carburetor to discuss that.

Hooroo to the guru.
Thanks to all the gurus who have helped me with very good advise.
I am happy to report the the Stihl Viking Ride-On is working as good as new.

I only had to take the carby off, clean it and re-assemble it.
Drain any oil/petrol and re-fill and it started right away.
I was ready to spend $840.00 for a new (probably Chinese) motor.
Money saved is money earned.
Thanks again, Mike, Joe and Grumpy.
Best regards from Lake Bolac
Frank

Thanks for posting the outcome gray nomad. Sounds like it was just dirt in the needle and seat. It is best to keep the inside of the fuel tank clean, and every few years remove the float bowl and clean it inside, where the junk accumulates.

I'll close this thread.