Motorcycling Again

Late last November an odd thing happened. I'd just arrived home on the Silver Numbat and placing her up on her centre stand with the usual creak and groan, I heard a plop from a couple of metres away. Investigating revealed the end of a large bolt with a nut on it. Not only unexpected, it was a bit disconcerting having never sheared a bolt that way before (not going to list all the ways I have torn one apart though).

The Cause -- wear grooves in the ground, hardened steel bushing seized against the needle bearing in the swing arm.

I gingerly brought the bike down off it's stand and wheeled it through to the de facto repair area next to the shed. Given that the swing arm seemed to be hanging on by only a few millimetres of shaft at one end, I decided best not to ride it until repaired -- losing a swing arm and then a rear wheel at 100km/hr is not my idea of a good time.

Unfortunately, I knew the bike couldn't be looked at until at least January. December was filled with a conference in Japan, a wedding in Adelaide, a deadline at work and then Christmas and New Years. January rolled around and I decided I needed to finish the house extension plans first. Fast forward three more months, plans are not quite finished but my patience at missing out on riding the motorcycle is.

Showing good taste in both humans and motorcycles, this redback decided the chain guard was a good place to hang out. Leave something long enough around here and they usually set up shop.

First thing is that the old bolt needs to come out. I should have realised that anything that would hold the shaft sufficiently well that it could be twisted in two was not going to release its precious easily. I think my fears of losing a swing arm and rear well headin down the freeway were unfounded. Still, not worth the risk :)

Seized bearings and a neat fitting shaft don't make for a pleasant extraction.

Rear wheel, chain and suspension-attaching bolts are removed in preparation. The shaft should come out using a simple 'tapping with a suitable drift'[1], however it resists my subtle, and then not-so-subtle, charms. Eventually I decide a more custom approach is needed. The shaft is 16mm diameter so I drill and tap an M10 hole into the end of it. A threaded rod goes into that and a nut, winding against a thrust plate slowly draws the bolt out with much angst, creaking and groaning -- some of it from the shaft. Eventually, all is apart and an inspection reveals groove marks on the hardened steel of the bushings, so it's likely the bushings seized and placing the motorcycle up on to the centre stand sheared the bolt.

A new bolt is not available as a part to buy so a scrounge through the wreckers -- same ones who had previously come to the rescue -- yielded one close enough that a favour from a colleague with a lathe at work modified it to a usable condition. An M16 nylock nut, larger than the one on the original shaft, just squeezes in to the space in the bike frame, so further modifications are averted. :) Other parts, the bushings, dust seals and a new chain guard for the swing arm, are ordered and when everything finally comes in, it's in to the mechanic who fits the new bearings with a hydraulic press I'm unlikely to ever own. :(

All back together again; new parts and cleaned parts living in harmony.

A replacement rear brake disc goes on instead of the legally-too-thin one that was there, parts get a bit of a clean and it all goes back together fairly easily, about a month after deciding to get her repaired and six months after putting her off duty. Unfortunately, the delay has meant I've essentially missed all the lovely summer riding and we are now well into sub-freezing morning temperatures. Still, I did a happy dance after the first ride . :)

[1] This is a typical phrase from many a vehicle repair manual. As long as you have a collection of about twenty steel bars, rods, bearings and sockets you'll usually find something 'suitable'. The 'tapping' is always repair manual humour.