Yamaha TMAX sidecar
In the neverending quest for more power….
In reality this is the rebuild of a rebuild, the original idea was to take the lessons learnt from my 125cc sidecar and apply them to a sidecar based on the 500cc Yamaha TMAX. Other than more power I was looking for better ride comfort, a tighter ‘fit’ around my wheelchair and general improvement in the fit and finish. While the little Honda has served me well doing 1000km a month as daily hack its replacement had to be as good around town while giving me more scope to travel beyond the city lights.
This is the starting point, my Honda @ 125cc sidecar, daily hack and sole means of transport, when this is off the road I’m stuck to the back of meatwagon taxi’s, sole destroying and expensive. Reliability and easy of use were the requirements for the new outfit.
Unfortunately TMAX sidecar build No. 1 was a dud although my 2 year old thought it a great climbing gym..
Build No. 2 involved turning the bike into a trike, removing the subframe and relocating the fuel tank. Modifications to my chair would allow it to travel over the rear wheel, up to the bars in their normal position.
Unfortunately the idea (my own) behind TMAX sidecar build No. 2 was also a dud although my 2.5 year old thought the climbing gyms I kept building her were getting better…
Priorities for build No. 3 were simple (1) it had to work & (2) after spending X+Y it had to be done as cheaply as possible.
What I had learnt from sidecar No. 1 and the trike exercise was, (1) get professionals, (2) write down / draw specs & (3) keep a close eye on the build.
With respect to (1), Dave Kellett the Brisbane (Australia) sidecar guru is charged with building the LL’s and attaching the sidecar to the bike and the guys in the workshop of my employer the CSIRO are to do the sidecar build. To keep the pressure on, Christmas 2010 provided a completion date that all agree could be met but I was doubtfull about that.
Considering point (2) I spent time with Google Sketchup to get my ideas on paper. Sketchup is a very easy to use Google tool, useful and free.
Unfortunately once tubing was bent and tacked and the rough outline of the cage was formed endless circular “discussions” started with the contractor employed by my work to do the job. These discussions were mainly about my ignorance and foolishness with respect to the design. Paying to have someone tell you your a dill is never pleasant and I was glad and relieved to pass the job over to Dave for the rest of the build. In hindsight he should have been tasked with doing the job start to finish. Anyway, here are a few photo’s of the cage under construction.
While the sidecar frame was being built Dave had removed the trike training wheels and constructed the leading link forks. LL forks serve to reduce the trail and provide greater lateral strength than telescopic forks.
These LL’s are Dave’s “light” version, downtubes are double walled thru the triple clamps and lower sections are box with three positions for the pivot. Trail is reduced by approximately 50% from original. Later photos will show the final result when powder coated. They are a work of art and the integration of the original mudguard is amazing.
In the following shots the bracing for the sidecar suspension is finished and the nose started. The nose will house the fuel tank with bracing back for the steering bearing.
Sidecar wheel lead is positioned at 20% of the bikes wheelbase and again the swingarm and pivot are all fabricated by Dave. Suspension is a coil over dampener from “something that was lying around the shop”.
As the rear sub frame and tank had been removed during the bikes brief trike incarnation I decided to reposition the tank into the nose. This makes filling easier, gives potential for more volume from a custom tank down the track and allowed us to lower the bikes seat to potentially make it more friendly for my little girl. Protection of the tank by framework and the front of the bike is pretty good, I’ve had a few people express concern about the location but I am happy with it myself.
Nose bars will be modified later when we seriously considered how to fit some body work.
Back from the painters and we are getting close now. It’s like waiting for Christmas when you’re a kid, you know the feeling, you want it done right but at the same time you want it. NOW!
Time killer for us was the brakes as they turned into more of a drama than they should have. I have the sidecar disc on the same hydraulic circuit as the bikes front brakes and I don’t touch the bikes rear as my left wrist doesn’t work. The block we had purchased to join two hydraulic lines into one had the internal hole drilled off centre. This wasn’t obvious until Dave noticed a persistent leak when pressurising the brakes. After stuffing around for several days and chasseing the guy who sold us the block, Dave discovered the off-centre hole and was able to correct it.
Brake issue number two was bleeding the quite convoluted line and getting a good feel at the leaver. This took days with the callipers up, down and sideways, tapping the length of the line to get every microscopic bubble out, then doing it all again tomorrow. And the next day. And the day after… We persisted with the original master cylinder before giving up and going from a 14mm bore to 16mm. Problem two solved.
Issue number three was a warp in the sidecars new disc. Either from a bad batch or from getting inadvertently touched by some thing hot. I rode it with this for a month with a shocking judder until the disc was machined and brake problem 3 resolved.
The photo’s show the paint job colour matched to my wheelchair. Had to gulp when I saw it the first time and put the sun glasses on, it has grown on me now. I guess it’s a matter of taste.
The nose has been modified to allow easier fitment of some bodywork which will be pretty minimal. I’m so in love with the tube work and welding quality that the bodywork we fit to keep the windblast out from the pants leg will sit behind the framework.
It’s may not be obvious, but in fitting the bikes subframe we have reduced the seat height by 50mm and moved it forward by the same amount. As well as hopefully giving a more compact look the purpose was to make it more friendly for my daughter when she is old enough to ride with me.
Lowering the subframe and seat meant a hole cut out of the underseat storage. I have found this tub extremely useful on my past bike so will need to replace the tub with some sort of storage. At this stage I’m leaning towards a topbox mounted on the pillion seat forming a back rest for the solo passenger. Underseat will be a home for reverse gear as we have direct access to the rear wheel. Some sort of small motor with wheel that is push onto the bikes wheel is the plan. Anyone have any other ideas for a sidecar reverse?
Delivery in Match 2011.
Skip forward a couple of weeks from these last shots taken in Febuary to mid March. I took delivery the day of the 1st test ride, a trip around the block, adjust the steering weight to position 1 from 3. Another spin around the block and pull in to adjust the relative position of the throttle / brake adaption I use. Final spin and all is good, I’m off home, 16km in a Brisbane summer downpour.
A couple of fine tuning sessions over the following two weeks to adjust the toe-in. We ended up with 13mm over the bikes wheelbase. With this there is the very slightest run to the right hands off but no major movement under power or off power at any speed. No headshake and tracks straight over all pot holes that I have hit so far (no steering dampener is fitted). I really can’t say enough about the handling.