New 26HP B & S motor dropped into older 24 HP body won't run right, why?
I bought a Craftsman mower from a guy off Craigslist. The mower originally had a 24 HP engine but the guy dropped a 26 HP 44P777 into it. When I went to look at it, it ran like a beast and mowed down anything that got in it's way. I loved it, bought it, hauled it home and it has not run right since. I have taken it to 3 mechanics with no success. One of them told me that there were two "governers" now, one from the original engine and one for the new engine that were fighting each other for control of the fuel distribution. One showed me that if you pull the line that runs from the valve cover to the fuel pump you can get it to run well but if you try to mow it boggs down. It seems to be sucking air and oil through that line and smoking when it does. None of this explains why it ran so well when I bought it. I changed the plugs and air filter. The third mechanic adjusted the valves properly, but none seem to understand what is going on or what has changed from the time I bought it till I got it home, a ride of about 60 miles. Any suggestions?
