Just picked up a free Honda g300 to shoehorn into my 606!! The only problem is it can't keep spark! When you ground the plug on the block it'll spark beautifully then all of sudden nothing. Pull the recoil start a few more times and boom, back to a great spark. Spark plug is missing the little screw on cap on the top but fits tight in the boot. Tried a different with the little cap but it won't snap in?! Would this be the cause of my problem?