Last year I picked up a old 97cc "Bug Racer" off Craigs list, and did the Predator engine swap, but kept the little engine. I just picked up a newer 97CC Doodle Bug off Craigs List. It's not running, so it was cheap and I couldn't resist. Looking it over today I pulled the spark plug and it is much bigger than what is in the Bug Racer engine. The two 97CC Hensim engines are both model HS152F. So I thought it's the wrong plug and I'll just put in the spark plug from the old engine. I did and it still won't start or even turn over a little. I got paranoid about the plug So I did a little research and The 2011 DB manual lists the spark plug model as NGK BP7HS with a 12.7 mm reach. Other sources list the plug for the 97CC as NGK BPMR6A with a 9.5 mm reach (I had a comparable Bosch WSR6F in my original engine). The BP7HS is about twice the size of the BPMR6A. Both plugs have the same 14mm thread spacing so they will "fit" either engine. Both are 0.7 gap. So, My questions (finally) are did Hensim actually change the spark plug configuration at some point? And if so how can I confirm which engine generation I have (i.e. serial #)? Or does the reach even matter? With the engine not starting I want to get the spark plug variable off the table.
