300zx 7 #1 Posted September 23, 2010 I am helping a neighbor with his sons mower. It is a Toro 17-44 HLX Lawn Mower with a 17 hp B&S OHV engine, 312777-0128-E1. It seemed to run OK at high rpm, but randomly pops at idle. We thought we could hear a compression leak and decided to check the valves (we later realized this engine has a compression release for easier starting, like Kohlers, and that is probably the leak we heard). We pulled the head and found oil fouling. The head gasket had been leaking between the cylinder and push rod galley (this seems to be a common problem). We cleaned up all of the fouling and carbon, lapped the valves, put on a new gasket, torqued the head to spec (at 6 different torques and finishing at 250 inlbs) and reset the valves (.004 intake and .006 exhaust). We started it up and it is better, but still randomly pops at idle. We thought the carb seemed pretty clean when we pulled the bowl, so we didn't initially clean it. After all of this, we went ahead and pulled the carb down for an overnight soak. Does anyone have any ideas and if not is there a good place to go for B&S help? Could the compression release be randomly cracking the exhaust valve at idle or could we have blown the new head gasket again?? I'm grasping at straws here as I write this thread!! Share this post Link to post Share on other sites
mavfreak 11 #2 Posted September 23, 2010 I will be watching this post cause I have same problem on to briggs Share this post Link to post Share on other sites
300zx 7 #3 Posted September 23, 2010 The carb cleaning made little difference with the idle mixture as we found it, 1.5 turns out(with a plastic cap restricting movement). We went a 1/2 turn in and it made it worse, too lean. 1/2 turn out made it purr like a kitten. So at 2 turns out it runs great. We had to set the idle down a little bit, but no more popping. Needless to say, we learned more than we wanted to about B&S OHV engines. Turns out the manual recommends setting the valves every year. If the engine becomes hard to start, ie, starter can't turn it over, the exhaust valve gap has gotten too wide and the automatic decompression release can't open the valve enough to relieve the compression. Share this post Link to post Share on other sites
