When you have to bolt up two metal parts with a seal or gasket between them, it's important that the parts are completely flat.  Thin metal parts like sump plates or the cover of the diaphram of the acclerator pump are bad about warping around the bolt or screw holes if they are overtightened.  This creates a gap in the area between the bolt holes and many times the seal or gasket can't make up the difference.

To make them flat again, grab a cheap sharpening stone (I get 'em for a buck or two at the flea market or on sale at Harber Freight) . . . they have a course and a fine side.  Use the fine side.  On smaller parts, hold the part flat and rub them in a circular pattern on the stone.  For larger parts, lay the part on you workbench and, keeping the stone flat, rub it around the part in a circular motion.  Stop every few seconds and look at the progress . . . first, you'll see the part starting to shine around the bolt holes.  The more you rub, the larger the shiney part will get . . . when the entire surface of the part is polished, it's flat.  Stop, clean it up and bolt it on.

I just used it on Homer's carb yesterday.  I cleaned the stuff that used to be gas out of it, and after I put it back together it was squirting gas out between the carb body and the cover over the accelerator pump.  I found a new diaphram and put it in, but it was still leaking . . . so I pulled it back apart and used the trick above to level the accelerator pump cover . . . no more leak!

I'll find a sump plate and bring it to the next meeting.  Since the torque setting is just a few inch pounds and most folks think the tighter they are, the less likely they are to leak, 99.9% of them have high spots around the bolt holes.  If you want them to seal, they need to be flat. 

I just used it on Homer's carb yesterday.  I cleaned the stuff that used to be gas out of it, and after I put it back together it was squirting gas out between the carb body and the cover over the accelerator pump.  I found a new diaphram and put it in, but it was still leaking . . . so I pulled it back apart and used the trick above to level the accelerator pump cover . . . no more leak!

I'll find a sump plate and bring it to the next meeting.  Since the torque setting is just a few inch pounds and most folks think the tighter they are, the less likely they are to leak, 99.9% of them have high spots around the bolt holes.  If you want them to seal, they need to be flat. 

These ideas work very well.  I do oil pump covers with my belt sander( not hand held sander) to remove the wear pattern the gears leave if I don't have a new plate. Check with some kind of straight edge.