I think you have this topic posted twice….So, will add more to my reply here…. Do you have the throttle cam synchronization set correctly? Is the carb just starting to open when the line on the cam is bisecting the roller? If the cam is pulled out too far, the roller will definitely hit and jam on the edge of the cam when you advance the throttle from its full retarded/stop position…
Looking at your picture, it kind of looks like the roller is still touching the cam way before the correct pick up point… There is a little line on the cam, this is where the throttle should just begin to open….Yes, I realize there is slop in this linkage, and just because the roller starts to move the linkage, that doesn’t mean the butterfly is starting to open just yet. But, yours looks way over-advanced. Granted, it is tough to tell from that picture, would have to see a picture looking down on the cam roller taken from the front of the engine….In other words, in most cases, the roller should not be actually touching the cam when roller is at the end of the cam….
Again, this may just be a throttle cam/pick up adjustment issue. You mention this engine was built from “parts”, so it may be possible that there is a mismatch of parts, but everything looks “OK” to me also…
