jedijody wrote a post regarding troubleshooting ignitions. It was intended for Rcexl, but thinking it will apply here as well. It's up in the "Newbie to Gas" thread at the top of this "Gas Engines" heading, 2nd page, post #36. You might get some ideas with a read through that?
http://www.rcuniverse.com/forum/gas-...rmation-2.html