Hi,

I have a Briggs-Stratton Engine that has a broken Connecting rod and I have ordered the new parts and I'm wondering if anyone has info as to what I will be up against. Do I need to remove the entire engine from the bed of the mower or just the top of it? By the way it's a B & S model number 286707 type 0437, 12.5 HP that cam with a Craftsman LT 4000 riding mower.

Thanks,
Craig

vertical crank? well yeah it'll have to come outta the frame, remove the pulley, and sump, and dig into it from there. remove the head to pop the piston out to install the rod. then again, it broke the rod, check for other internal damage before you go throwing money into it, for nothing.

Check the cam over real well on this engine, the rod has been known to bend them but show no obvious damage.

Mike

Bugman & Mike,

I'm not sure it makes a difference but it's an electric start and I've got the piston out without taking the motor off. The cylinder walls look smooth. I got the mower for $0 so if I get it running for little money it's all good. I bought a replacement rod, piston, locking pin and engine gasket set for $60. I thought I could somehow replace the connecting rod without taking the whole motor out but I guess not. I've never done this before so I really appreciate you gentlemen taking the time to post your thoughts.

Craig

If the rod broke the engine was probably run low on oil. If so, your rod will probably look something like this:

Broken Rod (http://hambone.homelinux.net/photos/broke_rod.jpg)

and your crankshaft probably looks something like this:

Crankshaft #1 (http://hambone.homelinux.net/photos/crank_1.jpg)

The markings you see on the cranshaft may look like scratches, but it is actually aluminum that was transfered from the rod to the crankshaft. When the engine is run without oil, the friction between the rod and crank is so high that it will become hot enough to literally fuse the rod to the cranksaft. When this happens, the rod is snapped right off and the engine dies.

Ok, now I'm going to let you in on a little secret. You can repair a crankshaft like the one above and have it looking like new in about 10 minutes. All you need to do is get some Muriatic acid (a weak hydrochloric acid) and a natural bristle paint brush and lightly dab the acid onto the aluminum until the acid stops "fizzing". When this happens, wash the cranshaft thoroughly with water and then coat it with WD-40 or a similar spray lubricant to prevent it from rusting. Now all you need to do is get some emory cloth and polish up the crankshaft to remove all the traces of aluminum. When all of this is done, your crankshaft will look something like this:

Crankshaft #2 (http://hambone.homelinux.net/photos/crank_2.jpg)

Trust me, this little trick works because I used it to repair this mower and sold it for $450:

Murray Riding Mower (http://hambone.homelinux.net/photos/newest_mower%20001.jpg)

Bugman & Mike,

I'm not sure it makes a difference but it's an electric start and I've got the piston out without taking the motor off.

Craig
well that could happen from it having a broken rod. if its too bad, take back the parts, or sell em, and find a good used one... e.bay maybe or somewhere like that has 12 or 12.5's on there alot of the time, or power it with something with more hp. as for the cylinder wall, looks smooth, well if it has a good wear ridge, expect to have to do a ring job, if you want to do it

The markings you see on the cranshaft may look like scratches, but it is actually aluminum that was transfered from the rod to the crankshaft. When the engine is run without oil, the friction between the rod and crank is so high that it will become hot enough to literally fuse the rod to the cranksaft. When this happens, the rod is snapped right off and the engine dies.

Ok, now I'm going to let you in on a little secret. You can repair a crankshaft like the one above and have it looking like new in about 10 minutes. All you need to do is get some Muriatic acid (a weak hydrochloric acid) and a natural bristle paint brush and lightly dab the acid onto the aluminum until the acid stops "fizzing". When this happens, wash the cranshaft thoroughly with water and then coat it with WD-40 or a similar spray lubricant to prevent it from rusting. Now all you need to do is get some emory cloth and polish up the crankshaft to remove all the traces of aluminum.

An old thread I know, but I tried this muriatic acid trick on the crankshaft of my 5hp Tecumseh, and it works like a charm!
After it was all said and done you would never have known the rod had seized up on the crank. :thumbsup: