[x3300]

I noticed that the output shaft of the trans was a bit tight to turn, and I had intended to go through it, so decided it was as good a time as any to take the trans apart put some new parts in. I won't go into much detail of how to do a rebuild since it has been well reported elsewhere.

I have this flange puller from Ed Korn's Cycleworks. I don't think it would be to hard to make something though.



Here's a side view of the puller.



With the flange off I used some heat and a plastic mallet to get the cover off and pull out the parts.



The new parts; 5 shaft bearings, some seals, a neutral switch, the critical shifter spring, a 1st gear bushing, and a 688 bearing. The front input bearing was OK, so I decided to not replace it. I also put in a new cover gasket.



I took the shift mechanism apart to replace the critical spring. I put a witness line on the cams with a Sharpie marker.



I also replaced the plastic detent roller with a 688 roller bearing as seen here. 688s are used for in-line skate wheels, so easy to find.



I used this puller to get the bearings off.



Here's the output shaft disassembled. I took it down this far to machine a groove to accept a circlip that will hold the front bearing on, a standard mod for these transmissions.



The circlip is an external 17x1. The DIN 471 spec gives a groove diameter of 16.2 mm, so I only needed to remove 0.8 mm off the shaft diameter.

Here's how I mounted the output shaft on a lathe to turn the groove. I ground the width of a standard carbide cutting tool down to about 1.5 mm, then made the cut with the right edge of the tool 18 mm from the bearing shoulder (17 for the bearing, and 1 for the circlip). The shaft was pretty hard, but I went slow and could make the cut with the carbide tool. I've heard of using a grinding attachment to grind the groove.



To make up a plate for shimming the bearings I mounted the trans cover on a mill and used the mill's DRO and an edge finder to get the relevant cover dimensions.



Here are the measurements I came up with.



And the resulting shim plate drawing to work with.



Here's the plate bolted to the assembled trans ready for shimming.



The bearing end clearance of each of the three shafts needs to be set using shims. The proper shim thickness is determined by measuring the depth of the cover hole that accepts the bearing, the thickness of the plate, the thickness of the cover gasket, and the height of the bearing above the plate.

  gap = cover + gasket - plate - bearing

Anyway, I could get it all shimmed up and reassembled without much worth reporting.



-x3300