Correct size shims to fit BTH KD1 magnetos and other BTH magnetos with similar housing - i.e. KD2, KH1, KH2 etc. See detail listing for more information.
These are the square shims to fit BTH KD1 magnetos, and other magneto's with similar bearing housnigs. They are used to shim the magneto armature by fitting between the main body and the rear bearing/cam ring housing. As you can see from the main photo - they are a perfect fit over a BTH rear housing flange.#
The lip of the BTH housing in the photograph that this shim fits over is: 2.165" (and our shims are @2.175" ID to fit over this)
We sell this shim in two thickness's - 0.008" (8 thou) imperial, or 0.004" (4 thou) imperial, so as with any shimming of magneto's if you require a greater gap you will need to fit multiple shims. Also - original BTH magneto shims I have seen were sometimes in steel and sometimes in copper. These are in proper shim steel - and the difference is nominal, as both are conductive. Please state which thickness shim you require when completing your online order in the Comments section
28/2/20: I am pleased to be able to offer these again - as they have been unobtainable to us for about 5 years.
Final Note: The inner diameter of the large circular cutout on these shims is @2.175" - which is correct for BTH magnetos. Lucas magneto bearing housings are of a fractionally larger diameter lip and take a slighlty larger shim than the BTH shim. I did attempt to very carefully linish out one of these 8 thou BTH shims with a flapwheel in a handdrill, while holding the shim vertical in a vice with soft jaws and holding the shim with my fingers at the top - as you can see from the last photograph - I was able to linish it enough to fit a Lucas NR1 racing magneto housing. Although i cannot tell you it was particularly easy - it took about 10 mins for an thou shim (and please follow all normal health and safety rules!) - but it did open up as you can see in the last photograph. For the 4 thou shim, I doubt you will be able to linish, but might be possible to trim with sharp scissors. So if you find Lucas shims are not available, this may be an option. However - as you might expect . . . if you wish to try one for this purpose - I will not take Returns if it does not work well! (note - I may get a batch of Lucas shims made in the future but no plans at the moment - i.e Feb 20).
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