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Discussion Starter · #1 ·
I posted my problem another thread. my other thread

Bottom line it looks like the 11hp Briggs Stratton has a warped head. I was wondering if it would be an easy swap to put a 12.5 Briggs/Stratton on the mower. I have found one for $75 and it does start and run and the fella will give a guarantee it won't run my mower.

A few things I noticed different:
1) there are two wire coming from underneath the flywheel while mine has only 1 wire. How can I connect this for charging?

2) the throttle, choke control plate (where the cable connects) on the side is in a different location but I think I can switch the old to the new.


How do I remove the bolt on the bottom of the shaft? is it normal thread (left loosy?)

How do I remove the pulley and the PTO clucth?

Thanks in advance for you assistance.
 

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Discussion Starter · #4 ·
I am finally getting around to getting this done. does anyone know the answer to my question about the wiring above?
 

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I did a 11hp B&S to a 14hp B&S swap this past summer. Had the same problems (questions).
To remove the bolt under the main shaft, mine was 6 sided hex. Under the flywheel shroud, there is a large nut, 1-1/4 or 1-1/2 inch.. Connects to the same shaft. Socket on top, allen wrench on bottom. Watch the knuckles. Left loosey / rightie tighie.
Once the lower bolt is off (lock washer and regular washer too), the PTO and pulley should fall off (once the belt is removed). Don't let the pto fall too far, it has short electrical leads on it that could pullout. They are both keyed, so watch for the key to fall out, too.
Cable 'block' should be similiar, just on other side of engine. The small stud on the insulator block may not be on the 11hp. That is a common point between the fuel shutoff switch and motor shut off circuit. Check the B&S website for specifics of each engine.
Two wires vs. one wire for battery. One wire is for the headlights, usually ac, if you got them. On the wires, is there a small 'bump' on them? That 'bump' would be a diode, that converts the ac voltage from the stator to dc voltage for battery charging. If there is an existiing 'bump' in the original wiring behind the instrument panel, all you need is a wire that has no 'bump' out of the new engine. Check the specific engine wiring diagram(s) on the B&S website for your specific engine to confirm wiring.
NOTE: The existing push-on connectors might not go together for different hp sized or model engines. You may have to hard wire it, after confiriming their correctness.
WORD OF CAUTION: Since you have a bigger (physically) motor, the exhaust may be positioned differently. Mine was about 1 inch more to the right, so I had to cut a notch in the screening on the engine compartment covering. Old engine exhausted on the bottom front, new one right side half way up.
NOTE: mounting bolts should line up okay.
 

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Discussion Starter · #6 ·
thanks for your reply.

what did you mean by "Socket on top, allen wrench on bottom"?

can't wait to give this a try.

I tried to get the old motor started without any luck. Took the replacement engine. hooked to fuel supply and used jumper cables to start. fired right up!
 

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Under the screen on the top of the engine, remove the screen by removing the 3 or 4 screws, you'll see a large nut, six sided. That is on one end of the motor's crankshaft.
Underneath the motor, the PTO is held onto the same shaft, just the bottom end, using an 'allen' headed bolt. The wrench fits into the center of the bolt head. I think it's a 3/8 inch. The allen wrench is an 'L' shaped wrench, but I suppose an allen head socket wrench would also fit.
Putting a socket on the top, allen on bottom, will allow you to remove either. On my rebuild, the allen end came off easily. To make sure yours does too, squirt some BP blaster or other liquid up into it and let it soak abit.
And watch those knuckles. Been there, done that. Only hurts for awhile.

"Fired right up"...you're on your way.
 

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Discussion Starter · #8 ·
went and looked at the motor today. the bottom bolt is a 5/8" head. it is just a bolt not an allen. I didn't remove the top. Are you saying the allen is the top or bottom?

Sprayed some pb blaster on it while i was there. hoping tomorrow or friday to get back and work on it.
 

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The hex head bolt is correct, I think he was talking about something else with the Allen head.

"I did a 11hp B&S to a 14hp B&S swap this past summer."

That will be some what different than going to a 12.5 hp.

Some Wheel Horses used a horizontal shaft engine, some used a vertical shaft engine. Assuming yours is a vertical shaft, check the crankshaft on the 11 hp first. SOME were shouldered to 7/8". Otherwise, the crankcase dia and length will be the same. As said above, the single wire with the "fat" place in it is the wire that should charge the battery. You could remove the flywheel and switch the stators but no point in going to that trouble.

NOW, the throttle box, where the throttle cable connects, the 11 hp and the 12.5 hp will work opposite to each other unless the cable comes up from the bottom on the 11 hp. Not sure about using the 11 hp throttle box on the 12.5 hp, the 12.5 will not work on the 11 hp as the 11 hp will not have a casting build up and threaded hole for the 12.5 hp throttle box.

Exhaust will be very near the same place but you should use a larger muffler with the 12.5 hp.

IF you are lucky, the electric clutch will come right off, sometimes they "grow" fast and then it is a problem.

Walt Conner
 

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Discussion Starter · #10 ·
Okay, thanks to all the help I got the motor swap done yesterday. It went amazingly well. The pulley and PTO clutch slid off easily once the bolt was removed. I was even able to move the throttle box from the old motor to the new motor. encountered a slight over revving problem but was able to make some adjustments and it worked great. Still need to modify the choke rod but I think I can get that done.

Motor starts effortlessly, made a minor adjustment to the idle and the lawnmower seems to be working very well.

The remaining problem is the charging system. As stated previously, there are 2 wire coming from the new motor where the old motor only had one. The attached pictures shows the new and old wires. The new wires are coming down from the top. They are red and black and have the white sqaure connector where their color switches. The original wire is the white wire with the round connector coming up from the bottom in the picture.



Can anyone specifically tell me which wire to use?

Some have mentioned that the headlights need to be powered AC power. The headlight wire comes from under the dash.

Can I measure the voltage off each of those wires?


Thanks so much for all your help so far!
 

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Discussion Starter · #11 ·
Bump, if anyone can tell me which wire to use I would appreciate it. I might get down to finish the job this weekend.
 

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The 'funny' round connector wire comes from under the dash? If that's the headlight wire going to the headlight switch, I think it would go to the wire that does NOT have that small bump in it, at the square connector.

You could check the voltage at the square connector, put the ground lead to the machine chassis, and the 'hot' meter lead on the separate wires. The wire that has the 'bump' should read around 12 volts dc when the motor is running. The other wire would be 12 volts ac and would vary as you change the motor speed.

The dc wire (with the 'bump') should go to the battery changing circuitry.
 

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Discussion Starter · #13 ·
The old motor only had the 1 wire. I guessing that it went under the dash and then got distributed and converted to the different circuits. I haven't been able to trace it yet. I might have to remove the gas tank and check under there. I did test the voltage on the wires coming from under the flywheel. I thought I was getting 24v DC off the red wire with the bump. I can't remember the voltage off the white wire. I was thinking it was something like 5v.

I will go down again and check again.
 
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