Skip to main content

Engine tip: Primary Gear Installation

Crankshaft primary gear can be easily installed -or removed-, with the use of a soft metal alloy piece, such as copper or aluminum. A 2mm copper sheet jammed against the primary gears will lock them in place and allow you to screw the crankshaft primary drive bolt.
Soft alloys will not damage the heat treated primary gears but be cautious that if the sheet thickness is insufficient, it may slip across the gears and damage the crankshaft seal or other components.


  1. I would discourage from using this method of jamming something between the gears. While this definitely does the job and blocks the primary drive gear to remove or tighten the primary drive gear bolt, this will put a huge load on the bearings and also on the crank shaft's RHS end (will the crankshaft still be true afterwards? You don't know).
    The preferred way is to use a gear holder, for the NSR250 its P/N is 07JMB-KV30100 and it looks like this:
    This creates a perpendicular load on the bearings which is what they are designed for I guess.
    I would think the second best method is to use a holder to be screwed to the clutch gear.

  2. Thanks for your comment. The aforementioned method is safe and most of the time you will find similar suggestions on OEM manuals as well.


Post a Comment