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Back in the end of middle school and 9th grade (before we had cars to work on) this is what we did for fun. the mowers sat in the woods for a few years until I got bored enough to mess with them again, but this time I was going to make a monster, now that I knew more about engines. the plan.... I was going to use the frame and axle from the old 45 mph lawn mower, but use the engine from the red mower, as it was overhead valve and had a full pressurized oil system with a filter. the old frame 
the engine a kohler 15 Hp OHV engine rated 29 torque! 
My idea was to fill in some of the area inside the cyliner head to increase the compression, then, while I had it apart, I would polish the intake and exhaust ports, as the factory machining was simplistic and didn't look like it could have possibly flowed good.... I also took apart the rest of the engine and cleaned it all up nice on the inside before re-assembly welding the cylinder head I first heated the cylinder head in my shop oven to make it weld better and also, to prevent cracking and warping I then proceeded to weld with the aluminum MIG welder, filling in all excess space in the combustion chamber I went a little overboard, so I had to mill out some of the excess weld, in order to yeild flow of combustion gasses near the spark plug and around the valves. 
once I got the rough shape I was looking for, and got the welds out from in front of the valves (LOL).... I rounded and polished everything up with the dremel. port polishing I used a die grinder with some sandpaper rolls to polish the ports and make them the same shape through the curve, instead of making a stupid right angle turn. I also polished the valve seats 
the cylinder bore this thing has a whopping 426 cubic centimeter displacement! lots of room for improvement from the stock 15 Hp! 
now that I had a nice strong engine, I needed to adapt the ignition to match the performance... the ignition works off a magneto style coil using a magnet in the flywheel, to advance the igniton timing, I just moved the coil about 15 degrees advanced from where it was. that made a huge performance increase more pictures soon! you can see videos of this mower on the other lawnmower page our old mowers you can see more about these wicked mowers at my lawnmower page that I made for a school project |
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Sarasota, FL USA |