Stage 3: The Spur Gear Housing

Follow the instructions very carefully (to be honest I think they are incorrect) and if in any doubt do not use the thread lock until you have checked that the clutch gear on the engine meshes up with the spur gear correctly. I am sure I followed the instructions to the letter and there was still about 1mm of spur gear that was not covered by the clutch gear of the engine (see picture) even after elongating the mounting holes for the engine so I could slide it along a small amount ( I do NOT recommend you do this).

I took the spur gear housing out after I found it did not mesh properly and although I could not get it apart because of the thread lock I cannot see where I could have gone wrong. I had definitely set the spur gear mount in the deeper section of the spur gear, and even if I had got this wrong the difference between the two side does not account for this much error.

Since I had bought a 2-speed spur gear housing I thought I would take one more look at the single speed I had built once and installed twice, as if I broke it taking it apart I could always install the 2-speed as a replacement. After searching the Internet for pictures I found two that indicated that my drive shaft appeared to be the wrong way round. Reversing the shaft puts the spur gear centrally in the housing. This however contradicts the picture in the manual which shows the flange on the spur facing away from the brake calliper mountings (see pictures). As a result of the reversal the spur gear and clutch gear now mesh perfectly.

Notes On Removing The Out-Drives.

1) Do not use a worn HEX key. If you round off the HEX inside the grub screw you are in trouble.

2) Grub screws are very difficult to drill out and soon blunt even a quality drill bit.

3) Use heat on the grub screw to soften the thread lock. Although be careful of the plastic spur gear housing.

4) It is possible to remove the out-drive from the shaft without undoing the grub screw. This can be done by using a hammer and drift to drive the drive shaft out from the middle of the out-drive while holding the out-drive in a vice. The advantage of this is, once separated from the shaft, more heat can be safely applied to the grub screw.

5) If you have damaged the grub screw use a new one on re-assembly.

6) Use thread lock sparingly.

The instructions for the assembly of the disc brake state a gap of 2mm between the head of the screw and the caliper. I think 1mm is closer to the mark. I have since bought a pre-assembled 2-speed spur gear housing and the gap between screw head and caliper is less than 0.5mm.

Poor gear mesh

My Spur Gear Housing Following The Instructions In The Manual: Can you see whats wrong?

My Spur Gear Housing After Shaft Reversal: The gears mesh perfectly now.

Excerpt From The Manual: Although the picture shows a different elevation, note the brake calliper mounting points for reference.

My advice would be to try it as stated in the manual first, and if your gears do not mesh properly, reverse the shaft and re-assemble.