Is there a head-clamp fitted to the frame? As felt vibrations are a product of resonances, a higher balance factor may not always help. PEI gave some good explanations on balancing and focussed on this specialSame trail and fork length as Domy. The trans is in stock position with the engine squeezed in, leaving enough room for the exhaust pipe to clear the front down tube. Primary chain is the same length as my A +twin.The frame is stock with the exception of a small cutaway on the top right rail to clear front intake rocker cover. The bike is very smooth up to 67 mph when a vibration starts. I balanced each 1/2 of the 270 deg. crank at 67%. Looks like it'll come apart some day to raise the balance factor. Neat riding bike at this point. I need more miles on it but our good riding weather in nearing an end for this year.
problem of engine manufacturers like JAP, whose engines were fitted into many different frames, showing
a very different vibration profile (with the same engine). See "Motorcycle Engineering", p.280: "....found in the original Vincent-HRD. singles. These engines ran very smoothly in the standard spring frame with a
factor of 66 %, but the speedway versions,......, vibrated badly in a cobwebby dirt-track frame until the factor
was reduced to 61%, this not very large reduction making all difference between a machine which was
passably smooth and one which shook itself out of your hands."