1979 Honda Z50R

This build was to be a ground up, start with nothing sort of project, so that’s exactly what I did. First things first I got a frame and a set of CRF50 engine cases. I knew I wanted a single shock rear suspension with a much longer then stock swingarm. So the frame was modified by firstly removing the original center support for the subframe and adding 2 side supports, not unlike a CRF50. The swingarm was the next piece of the puzzle and elected to try my luck with a generic pitbike swingarm that I found on eBay. Everything was lining up perfect, but then discovered I was going to need a 210mm shock to fill the void in the rear. Turns out a Honda ZB50 (Monkey R) uses a 210mm rear shock. I ordered an aftermarket performance shock from Asian Concept that utilized a nitrogen reservoir as well as compression and rebound clickers.

The front end of the package is comprised of a set of Giovanni pitbike forks that were drained and refilled with heavier 20w fork oil. Front brakes include a Thumpstar caliper and master cylinder, with a 190mm rotor bolted to a Minimob Racing one piece billet 10” wheel.    An Acewell 2702 model gauge was used to monitor speed, rpm and other essentials for street cruising.  Installation was fairly straight forward for anyone with 12 volt wiring experience; the gauge also offers a blue backlit display which looks fantastic at night.

The first power plant installed in the completed bike was an 88cc top end with a ported E22 head.  The bottom end comes courtesy of 2005 Honda CRF50 engine cases with an AHP 4 speed transmission with manual clutch.  This engine combo with 16/37 gearing and 10 inch wheels was capable of speeds around 85kmh at almost 10k RPM.

With just over 1000 kilometers on the Acewell odometer and one season on the mean streets of Winnipeg, it was time for some upgrades for the next season.  I was very happy with the way the bike handled and had great ergonomics for my 5’7” stature, so I knew the main focus was going to be making more useable power.  From the beginning I wanted to keep this bike going on a working mans budget, the most inexpensive way I could upgrade to a little more punch was to upgrade to 117cc’s.  The upgrade from 88 to 117cc’s required the engine cases to be bored to accept the larger cylinder sleeve from the new 54mm bore cylinder.  A TB 51mm stroker crankshaft was also installed. The next item completely blew my budget idea out the window, a Takegawa Special Parts clutch to handle to increased HP’s.

With almost 1500kms on the odometer now, I am very impressed with the power increase and actually had to change my gearing to better match the power output.  The entire bike handles incredibly well and performs flawlessly with a strong pull out of the bottom end all the way to the edge of the rev limiter.

After

(click to enlarge)