I bought a used PB-2100 from someone recently. It ran pretty good but the carb primer bulb was cracked. I replaced the primer bulb but now I can't get it to start. It's not even close to firing. I thought maybe I fouled a plug from all the cold starting so I replaced it. Still no luck. I did notice that there was a thin clear gasket that was hard to position when I replaced the primer bulb. I've tried re-positioning it several times but I still can't get it to start. Any suggestions before I take it in to the shop?