marathon 4 cycle no power

[1970buick]

1994 Marathon 4 cycle. No power and will only creep along at about 2 miles an hour. With air cleaner off, white smoke comes out of the carb when I let off the go pedal. Seems as if there is a good amount of sputtering and slight backfire. I put on a new carb and adjusted the valves to .004 and it did a little better. I read on here somewhere to put vice grips on the fuel line to the carb and it does run stronger but then obviously bogs out. Any ideas? I haven't checked compression. New fuel filters installed, tank cleaned and pick up tube cleared, new gas, all new hoses. No real smoke coming from muffler to speak of

[Spicyunicorn]

I'd start with compression check and it's rare but I'd check make sure cam belt didn't jump and throw off cam timing

[Gearhead1956]

Originally Posted by Spicyunicorn

I'd start with compression check and it's rare but I'd check make sure cam belt didn't jump and throw off cam timing

I 2nd that! compression check, timing check.