Help please. I've had my petrol 80 series cruiser about 6 months and it hasn't missed a beat. BTW it's not duel fuel. Last week the front muffler rusted through so I had it replaced. I wasn't aware at the time but the exhaust place just welded a straight bit of pipe in there. Maybe this is normal practice, I'm not sure. Anyhow when I went to start it, 3 times in a row it started but after about 5 seconds it stopped. After that it was fine. It has never done that before. Yesterday I drove it around for a few hours and then I went to start it and did the same thing. Only difference is that this time it won't run. It starts, revs up as normal for a few seconds and then dies. Trying to keep the revs up doesn't make any difference. I had it towed to an auto sparky and after 4 hours they still aren't sure what's wrong. Any Ideas ?