Girder Fork Specifications
 
Listed below are the dimensions of the bushes and pins required during the overhaul of M20 front forks. Also included are the specifications for the fork main spring and figures for testing the poundage.
 
Fork bushes
Outside diameter… .688”-.690”
Inside diameter… .5615”-.5630”
Length… 1 7/16”
Clearance..Bush to link pin… .0005”-.004”
Acceptable clearance limit at overhaul… .005”
Condemnation limit (bush to link pin)… .010”
Ream bushes to finished size after fitting.
Quantity… 4 off
 
Side fork damper disc thickness (new)… .110”
Replace when wear exceeds … .015”
 
Fork spring
Free length before fitting… 10”
Free length condemnation limit… 9”(or poundage as below)
To compress the spring to 8” a load of 320-330lbs. should be required
Condemnation limit… Condemn spring when a length of 8” can be achieved with a load of 300lb. or less
Minimum distance between coils when assembled… 1/2"
 
Fork links

Dimensions between centres (top links)… 3 3/8”
Dimensions between centres (bottom links)… 3 3/4"
Inside diameter (plain holes)… .323”
Condemnation limit… ..330”
Threaded links…5/16”x 26tpi Cycle thread.

 
Ian Wright