To eradicate the hassles caused by primary gear front bush seizure/wear, this bush has been developed to be a straight replacement with no post-fitment corrective size machining required.
In race use, the bush can become seized/partially seized on the crankshaft, spinning the bush the primary gear journal and usually preventing gear selection. Simply replacing the bush and machining the bearing surface to give the correct bearing to crank clearance will often not resolve the problem since it is likely the journal itself will be damaged/become over-sized. Having a new standard-type bush fitted can also be costly, as the bush needs machining absolutely concentrically with the rear bush - a time-consuming job.
New primary gears are very expensive, and replacing gears with worn bushes for a good used one is becoming a problem with the decline in available replacements. And again, getting a new bush fitted and machined is very expensive.
To solve these problems this bush is designed just drop into the gear and to spin in the journal and on the crank - thus eliminating and fitting/machining expenses and further seizure problems in use and making re-use of the available used units easy. Tested over three full racing seasons it has proven 100% reliable.
Remove old bush - by pulling it out if it is already partly sticking out or is loose, or by using a die grinder to cut through the bush taking great care not to cut into the journal.
Clean journal with fine abrasive cloth such - as Wet & Dry or aluminium oxide cloth - to remove any surface blemishes, creating a smooth surface for the bush to run on.
Lightly oil bush and insert into journal, then shim primary gear end float in the usual way.