I just got a KRW magneto Gap Gauge and have been reading how to use it. Seems rather simple, but I read that "Setting the field ring after setting magnet height with the KRW gap gauge only works if the tool is calibrated AND the rear main bearing thrust surface was machined using the KRW procedure." That said I have not found any information about how the rear main bearing is machined/set? Thanks Mike
The idea is to get as little movement (back and forth) of the crankshaft. If you have excessive crank thrust you wont get a true reading when you try to set the magneto to coil height.
Ideally this is done when setting a crankshaft with new babbitt in the mains.
What you can do if you have some movement and you have a good crank and Babbitt is to buy a new end cap and get the correct clearance that way. You may have to file the end of the cap some but you can set the clearance that way and it will work fine.
This has been done since way back when and worked well a lot of T's.
You didn't say if your engine has been rebuilt but if it was it should be OK.
Well.... the engine is a little tired. The rear main cap has been replaced to improve the crank thrust. I said improved, it is still slightly under spec, but good enough for this engine.
When you say back and forth movement are you talking about front to back movement of the crank, with respect to the block? I suspect what this is all about is to get the crankshaft flange at the proper distance from the block?
When the bearing is machined correctly, by the KRW method or otherwise, the flange will be the right distance from the block. Even if yours is not exactly right, the KRW gauge will get you close enough to make a small correction after checking the gap with the transmission installed.