CT-70 With 110 Power

After many engine swaps and performance upgrades on the 72cc engine, I was satisfied with it's street performance, but still not satisfied with it's poor performance off road. I wanted a engine that had a lot more power, and at least a 2 speed high/low gearbox like the CT90 and CT110s. Trail 90s and 110s were out of the picture since they were too large and bulky and ST90s did not have no 2 speed gearbox. So I decided to swap in a brand new ATC110cc engine purchased directly from Honda.

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The complete conversion process took about 1 month to complete. The engine cases and  engine bracket had to be machined to fit the CT70 frame. The hardest part was wiring up the engine. I had problems with the battery discharging overnight and also the charging system not working. One time I test rode it and suddenly the engine would just die! Luckily I was not far away from home. After adding a couple diodes, jumper wires and resistors, I finally had the charing system operate correctly.  The custom air filter canister consists of a 3" dia steel pipe with a custom machined and polished aluminum end cap with the intake port offset 3/4" from the center. I chose this route over using a K&N air filter to keep the original CT70 look. With this engine bolted on the CT70, this bike is a rocket. A lot more power than the CT70, CT90 or even a CT110.  Acceleration is fast, quick and responsive. This engine has full pressure lubrication to all engine parts including both gearboxes. This engine has no points or condensers but uses electronic CDI (Capacitor Discharge Ignition). I have modified this engine with a Takagawa Hyper CDI unit which has an unrestriected engine RPM govenor, upgraded high output ignition coil for a more powerful spark, NGK Racing Cable and low restriction air filter unit. I am currently working on a 1 1/8 " stainless steel mandrel bent exhaust system with Yoshimura muffler. Maximum is still undetermaned since the engine has not been broken in. I have taken this bike up to 45 MPH  easily. With the main transmission in first gear low, subtransmission in low range, maximum speed is only 5 mph. This provides SO MUCH TORQUE which is perfect for those steep trails. I must be very careful with the throttle. The torque WILL easily bend the CT70's stamped thin wall sheetmetal frame. This engine provides the best of both worlds: High speed for street riding and high torque for trail riding. Honda should of had this engine originally installed in the CT70. I have seen in some Japanese magazines that Honda made a 70cc OHC version engine with an additional high/low gearbox just like the CT90/110s. It's weird that Honda never exports the good stuff to the USA. This bike has now been sold. CT90/ATC90/CT110/ATC110 Conversion kit for CT70 available. Click here

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