Hart Par 18-28 problems with starting after carb/mag reb

A neighbor asked for some help on a Hart Par 18-28. This tractor hasn't ran in years. Cylinders #1,#2,and #3 seem to have pretty decent compression. I would say #4 is on the weak side. He did have the mag professionally rebuilt as well as the carburetor. The magneto and carburetor are all back on the tractor. I took my John Deere 70 over and we belted them together. It does not want to run. It will pop, bang, and belch once in a while, but not really run. If you take the spark plugs out and lay them against the engine block/head the magneto will fire them when the engine is cranked. I guess my questions are: 1) It appears that there is no timing adjustment? The magneto just bolts down to the piece of iron under it and that is it - no advancing or retarding - is that right? Top dead center on # 1 cylinder seems to be right at the time # 1 on the magneto fires. Secondly, the throttle butterfly doesn't seem to open as far as I would like. That throttle linkage behind the carburetor is very unusual. We did shoot some oil in the spark plug holes to seal things up better. Have tried a squirt of gas in the cylinders. What would you guys suggest as further trouble shooting options as we try to get this Hart Par running? Thanks you.

Well I would guess from here that your mag is out about 180 if it is just belching and popping with a bang occasionally. Also check your fuel flow from carb bottom plug should fill a pint jar quickly. If not then you have a flow problem also.

Sounds like ignition timing 180* out, if that's possible with the mag drive. Some will go only one way, some will go 180, some time with a gear like a distributor.

It can also be cross wired.