slmjim+Z1BEBE wrote: Many less-well-equipped hobbyists don't own V-blocks or dial indicators.
An alternative would be to place a sheet of glass on a flat tabletop, for instance, so that the glass is evenly supported underneath, and slowly rolling the rod across the glass while observing any gaps that appear & disappear as the rod is rolled. A grease pencil or felt tip marker can be used to mark the high spots.
slmjim & Z1BEBE
Agreed, many won't own these items but they can be located or fabricated far more easily than finding something like a lathe. While using a flat piece of glass or table top will show you any curve or bend you still have to work with something to get the bend removed and it will no doubt require some form of support for the part. It's one thing to know where the bend or fault is, but that doesn't fix it. Once you know the item is bent the real fun begins when trying to get it straight. More than a piece of glass while be needed unfortunately.
To the OP, if you know the shaft is straight as has been pointed out you can pretty much figure the plate is at fault. If you can get the rod into the plate and it still moves, you may want to try and put some lapping compound inside the bushings to open them up just a little bit. Don't go crazy with the lapping compound though and make sure you get the compound completely removed when finished. Another idea would be to take some emery paper or crocus cloth and polish the shaft where it rides in the bushings. Any amount of corrosion can effect clearance and sometimes just polishing a part can really help it move better. I would make sure to lube these bushings when you put it all back together. Now if the shaft won't turn or rotate at all when you have it together that will require some further investigation. I looked at a spare carb plate that I have and the bushings are staked in place so replacing them could be problematic, but not impossible if it came to that. I don't know if your bushings are staked in place though. Good luck with your project.
Sometimes very old lubricate in the bushings transform into like glue and stick with the rod. Before i would use any lapping compound try to clean the bushings with a Q-Tip and dilution like aceton or similar.