My '46 U has started running very lean on the front cylinder. The plug colour is totally different to the rear. The rear is nice and dark with soot around the edges, the front is clean with no deposits and almost pinkish colour electrode. A cold compression test came up at 70psi. There's no noticeable signs of leaks from the head gasket area and no visible cracks. She's running on both cylinders but not smoothly, lots of popping and banging.
My first guess was inlet manifold. I tried spraying carb cleaner around the inlet to see if it drew it in and started to race but it made no difference.
Anything else that I've missed? My thoughts are a leak on the inlet at the front manifold nut. If it is the inlet do I need new parts or just a clean and reassemble? Do you use a sealant?
Many thanks, Steve