Graecross Jackaroo MTB

 

2 mystery bosses here closest to the seat. What do they do?

Hi

Last week I was at a tip shop and as well as dropping off stuff, just could not help myself and bought a bicycle for the grand sum of $10. It is a vintage mountain bike, and they are popular in the city of Melbourne these days - even one that's tidied up still costs less than a new bike, and they can be quite stylish with interesting parts.

This one worked fine straight from the shop - I needed to pump up the tyres but there was a slow leak in the back.  Anyway, I thought I'd post a few "before" pics to show its original state. I had no luck cleaning rust from the handlebars, and a handlebar swap is all I've done except buy new tyres and tubes at more than 10 times the cost of the whole bike!

There is a police identification number written enthusiastically into the stem, frame, seatpost and cranks, and this is an Aussie made bike: with a name like Jackaroo how could it not be?

A few others have found it worthwhile mentioning Graecrosses including https://mtbtimeline.com/wiki/grae/start which seems to list almost every early mountainbike brand. "A New Recyclist" talks about fixing up a Graecross racing bike here, https://rustybikebell.wordpress.com/2014/01/20/a-garden-gate-graecross-the-pro-ten/ . A passing reference is made in Suzi's blog here https://www.suzyj.net/2014/02/ . I'd never come across this Australian blog before which is long running and seems to have morphed from making bicycles to coding and computers.

Anyway, the parts on this one seem to be very nice and durable. The covers on the shifters are missing, but what the heck, they still work! Will report more as things are cleaned and fixed up.

Painting Day

 

Hi

Today I have been painting bike bits in between other jobs. I started on this a few days ago and kept on with it today - it was 22C which is quite warm for early September here so I had every chance of finishing it well. To be quite thorough and add a bit of jazz, I've painted the bottom bracket adapters at the back. To finish things off over the next few days, I will use new 3d print material and heatshrink from Jaycar. Happy with the way things are going up to now. I put in a picture of the old bike and am currently making pretty much the same thing.

Back stopper clamped to frame - its about to be used as a drilling jig.

After drilling 

All the back detailing done in red including the top frame separators.... 

and the back stopper, wheel spacers and back plug. All completely unnecessary! But to do a good job you need to try as hard as you can.

Front stopper design just finished......

and now printing on my 3d printer.

 Update Sep 2. 2026 And here is today's bike work! I worked around emailing about tax returns, shopping at a supermarket, eating lunch at a caf, emailing an OzHPV challenge ad to a newspaper, putting out the rubbish and paper recycling and tree cuttings, painting a planter box in the front garden and having an afternoon grandpa nap. Actual bike work was modifying end stopper designs, printing and fitting end stoppers, refitting the painted bottom bracket parts, and swapping over black frame spacers for new red ones. Happy with progress.

 The bike is all painted now and I'm very happy with it. The last part to arrive was a wide bottom bracket bearing which replaced a spacer version I'd put together. During assembly I put heat shrink in 2 places on the cables to keep them altogether and slightly more aero. Its debut ride as a finished bike was over to my son's place only 2k away but no problems. Maybe a bit creaky, I'll try to tighten up all the bolts in the steering system. 

There's a lane nearby which provides a nice background  of corrugated iron, and I took a few shots there including selfies. The paint's already a bit damaged but I'll fix that as soon as I can. Now I've pumped up the tyres and can enjoy riding it.

Regards

Steve Nurse 

Cruzbike Sigma Repair

Ready to go

Update Aug 28, 2026: now listed on ebay for a 1 week auction, pickup from Melbourne, Australia, with start price under $50  here is the link, https://www.ebay.com.au/itm/147522846188 regards
 

My friend George passed away over a year ago, and he left a considerable number of bikes for his wife Christine to deal with. I've already passed on 3 of his Linear recumbent bikes with 2 of them raising money for OzHPV. I recently received another 4! At the moment I'm tackling the Cruzbike Sigma.  

This is not a typical Cruzbike. It is a brand that originated with John Tolhurst from Perth, Western Australia with the sale of a conversion kit to make a front wheel drive recumbent from a Y-Frame mountainbike. Now, under Jim and Maria Parker (USA), Cruzbike is a leading recumbent manufacturer, still making front wheel drive bikes. They only made one rear wheel drive bike and this is it.

Firstly to describe the bike I'm repairing and its problems: 

The back tyre was flat and that's fixed now.  A guide to the SRAM Imotion 9 gearbox in the rear hub showed me how to unhook and rehook the gear cable to remove the back wheel.

Seat base as drill template for Merbau timber.

 

The top part of the seat was cracked - the seat is one of the only parts the Sigma has in common with other Cruzbikes and this problem is relatively common - see here !  My fix was to make a replacement top seat part from Merbau  and strong plywood timber. I used the lower part of the seat as a drilling template and have done my best to alleviate stresses using rubber strips as suspension and metal plates to distribute load. I had some velcro strip, and the last step was to glue that to the timber to make the seat pad stick.

 

The rack and rear mudguard was supported by cable ties fastened to the seat struts. This made seat adjustment difficult. The mudguard mounting points were changed, it was cable tied to the rack, and the rack is now supported by a strut which bolts on to the frame. Quite proud of that and it looks good, and the seat can be adjusted easily now..

 I 3d printed 2 bar stoppers for the bike so the mirror that comes with the bike can be fitted either side. As well the drilled light bracket at the front has an adapter converting it to 22mm handlebar size, and a Cygolite rechargeable light is included. Rear  / functioning battery taillight / reflector and bell also installed, and the bike's original wireless speedo is supplied loose with batteries already fitted.

 

So here is the rebirthed bike out on its maiden voyage. Everything worked well but the steering takes a bit of getting used to (after about 3k on it I found it easy to ride). I haven't done all the work I can on it (for example 2 cables should run through the large lower frame tube but they don't) but I'm satisfied with what I've done.

 

There are some remarks about the handling in the  Cruzbike Sigma Forum Page here, and an earlier post here describes John Tolhurst's design intentions for the bike.

 

I was intrigued by the lettering and designs on the Sigma, and one sticker says designed by John Tolhurst and Ron Witt.  I googled Ron and soon found this page, which describes Ron's strong desire for a recumbent bike that started after a bike accident when he was 16. The page also describes the Flash Recumbents which came from the Perth suburb of Midland and were made from about 1982 to 1992. (I had heard of Logo Trikes from Western Australia, but not Flash!) One of the Flash bikes shown in the picture has large wheels and remote steering in the centre of the frame, a bit like the Wilson Bikes made in Melbourne.

Finally, a recent Facebook post from Glen in WA indicates there are about 3 Sigma Cruzbikes regularly on the road in Perth,  and a few extra ones lurking in garages.

I plan to sell this bike on ebay and will get the  auction going in a week or so with proceeds going to OzHPV.

Regards Steve Nurse