Reason for modification: All all HD Sportster/Buell gearboxes have reportedly got a problem! The main output shaft is hollow and carries inside 2 sets of needle roller bearings that in turn support one of the gear cluster shafts. Both the shafts therefore turn at different speed hence the need for the bearings. The problem is that the outer bearing is fitted in such a way that it gets little or no lubricant from the main box. This can result in the bearings failing. Given current labour and parts prices this will effectively write the bike off!!!!!!!
The Fix: Fitment of the “Maz” Gearbox output grease/oil nipple conversion. This unit is available from The Emporium some where near Manchester.
There is a “cheep skate” alternative for those who should know better but don’t but I will not cover that here.
1) Tools required:
Torx driver, knife, large flat bladed screw driver, socket, Drill, drill bit, small syringe or grease gun, paddock stand (optional) and copper mallet.
2) Parts required:
The “Maz” conversion plug and nipple assembly (approx. £20), HD transmission lube. Given a lathe and the ability to measure accurately the dimensions of the original seal you could machine your own plug up. Maz's part shown below.
Remove the front sprocket cover using the appropriate torx driver.
4) Removing original seal:
Locate the original seal that sits in the middle of the front drive belt sprocket and cut a slot in the centre of the rubber seal. Insert a suitable flat bladed screwdriver and carefully leaver out the seal.
5) Fitting new blank plug and nipple:
When the original seal is removed ensure the all dirt and corrosion has been removed from the end of the shaft. Do not allow any dirt or debris to enter the shaft. With the inner shaft now exposed check for any signs of bearing failure. Any “blueing” of the inner shaft would indicate the outer bearing has at some point over heated and the bearing has, or is about to fail (go to Maz).
If there is no sign of a bearing issue then using the ½ drive socket and the copper mallet carefully drive the plug/nipple assembly in to the end of the output shaft (Nipple pointing outwards). Ensure the plug is fitted straight and does not “cock” over. Maz designed them with a thou interference fit, as the plug is alloy, and a tight fit, it will expand more than the steel shaft when hot, so in effect, will stay put.
6) Front pulley cover modification:
It is now necessary to drill a hole in the front pulley cover to allow for the grease nipple which will just poke through the cover. This hole need to be big enough to allow access to the nipple but small enough not to allow your trousers to get court in the pulley. I used a centre drill bit as shown because these do not “snatch” on the plastic like twist drills do.
To identify where exactly to drill just place the cover back in place using the fixings to hold it lightly in place and spin the back wheel (no not by doing a burn out – I am assuming you put the bike on a paddock stand). Now remove the cover and you should have a “witness” mark showing you where to drill.The mod can be finished off by fitting a 1/2 rubber blanking grommet in the hole where the nipple is accessed through.
7) Lubrication methods:
Maz recommends the use of a grease gun filled with HD transmission fluid I use a small syringe fitted with a tight fitting short length of rubber hose. The reason I use a syringe is so that I know exactly how much lube I have put in. LM grease can be used with care. 5cc (of transmission oil or LM grease) on a regular basis should be sufficient.