Author Topic: 11HP overhaul  (Read 2579 times)

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toadson

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11HP overhaul
« on: July 09, 2006, 11:45:44 pm »
Hey guys Im new to this forum and lawnmower racing in general. I was planning on building a gokart, but came across a Murray mower with an 11HP Briggs. The mower is not running and was only 30 bucks so I bought it. Apparently gas got in the oil and the engine blew. The cylinder is scored and I have not checked the crank yet. Im assuming it is probably bad as well. Would you reccomend rebuilding this engine or should I look for a 12 HP? I'm not going to actually race this mower, I just want it to ride around for fun (I still want to make it quick). I may end up parting it out for my gokart. Thanks for any opinions. Also, I wouldnt mind if someone could tell me a good place to buy Briggs parts. Thanks!

Offline johntaves

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11HP overhaul
« Reply #1 on: July 11, 2006, 03:43:19 am »
I got a MTD with a blown rod. I took it apart and I think I was able to figure out its last moments of life. The piston was at the top and the rod was disintegrated. There were dings on the bottom of the piston that matched the crank counter weights. I think the rod heated up and turned to butter. On the last few power strokes it must have gotten shorter so that the piston hit the counter weights. Finally it didn't have enough strength to pull the piston back down and it separated. In short, it is fun to take them apart and see what happened.

I got some hydrochloric acid and used it to burn off the aluminum remains of the rod that had melted to the crank. I then lightly sanded it to remove two dings that had managed to raise some of the metal slightly. There was some minor damage where the flying moten rod crashed into things, but nothing that couldn't be cleaned up with a file. I ordered a new rod, from www.briggsandstratton.com and put it all together. It runs great.

I tried to find a used rod, but had no luck. Actually, I did have one, but I didn't know it. Someone gave me a 12hp flat head that probably had the same rod as mine. At the time, I had not found this site and thus didn't read some of the posts where George explains what parts will interchange. I just assumed that my 14.5 ohv would have nothing in common with a 12hp flat.

I replaced the varidrive with a transaxle and was clocked at over 30. I am now replacing the transaxle with a 700 trans, just for the sake of making it quieter, more responsive (less rotational mass), and easier to shift.

The summary of all this is that it's fun to get a dead motor running again, a lot of parts interchange so you shouldn't have to buy new ones, the 11 hp should get you going plenty fast, and as you make your mower faster you'll discover ways to improve on it.

You might as well start by making a $30 engine run again.

jt

 

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