top of page

How to Correctly Shift the Semi-Automatic 4-Speed Clutch | CSC Wolf 125 and Honda CT125

The ingenious “semi-automatic” clutch makes riding simple – or challenging for experienced bikers!


Honda introduced the CT90 back in the 1960’s with a revolutionary semi-automatic clutch. This original trail bike has since been updated into the modern 125cc from Honda and Zonsen. Unlike scooters with variable-speed, direct drive transmissions, these small motorcycles utilize a multi-gear transmission including a clutch. However, the “semi-automatic clutch” does not require a hand lever. Shifting between the gears is controlled entirely by the foot lever.

The semi-automatic clutch was a stroke of motorcycle marketing genius.


For the first time, a small motorcycle was designed and targeted for NON-motorcyclists! The original CT90 was advertised to prospective riders who had no experience and no interest in larger, more powerful motorcycles!

Since the genesis of the CT90 in the mid-60’s, other manufacturers around the world have adopted, refined, and perfected the semi-automatic clutch. This design removes the intimidation of larger, more powerful and complicated motorcycles.

But - don’t forget – the “semi-automatic clutch” is STILL a clutch.


The motorcycle transmission is shifting between separate gears. The motorcycle rider must choose the right gear to match speed to the riding conditions, from a dead stop to traveling uphill and downhill. The “semi-automatic clutch” only makes this process easier – at least for the inexperienced rider.


But experienced motorcycle riders need to unlearn their shifting habits. First, the shift pattern is completely different. Instead of the “1-down, 4 (or 5) up” pattern common to conventional motorcycle gear boxes, this transmission uses a straight 1-2-3-4 shift pattern. From neutral, first gear is one click DOWN on the toe lever, followed by 2nd, 3rd, and 4th gears. Then, using the heel-toe shift lever, down-shifting from 4th gear down to 1st is accomplished by four clicks DOWN with your heel.

The shift pattern of the 4-speed gear box with the semi-automatic clutch takes some practice to overcome the habits you learned when shifting the standard 5-speed or 6-speed motorcycle. But the larger difference is how the clutch engages the gears as you accelerate and decelerate through the pattern.


With a conventional clutch, you release the clutch lever slowly as you open the throttle to engage first gear. Every motorcycle rider learns how to apply the right amount of throttle to avoid stalling the engine – or too much throttle and popping a wheelie! In contrast, the semi-automatic clutch is controlled by the foot lever. From a standing stop with the transmission in neutral, you simply click DOWN into first gear. The engine will happily idle and will NOT stall! When you are ready to ride, you add throttle, and the gears engage to drive the chain and propel the bike forward. As you gain speed, back off the throttle, then click down to the next gear. The semi-automatic clutch smoothly engages each gear in succession. Similar to a manual clutch in a car or other motorcycles, you only need to reduce the throttle momentarily to allow the higher gears to smoothly engage.


It couldn’t be easier! First gear with the semi-automatic clutch operates more like the automatic transmission in your car. You can sit, idling indefinitely with the transmission in gear. The engine will NOT stall. You can immediately see the advantages for stop and go riding around town – or riding on steep, rocky, or muddy trails!

The semi-automatic clutch requires a slightly different shifting method as you downshift through the gears, 4-3-2-1.

With a standard hand clutch, the rider downshifts by releasing the clutch lever while simultaneously “blipping” the throttle. As the motorcycle slows, you need to ADD throttle to match the engine RPMs with the lower gears. Again, this process is fast and mostly unconscious for the experienced rider.


New riders often have trouble downshifting the semi-automatic clutch. As they slow down, they heavily stomp on the heel lever and force the transmission into the lower gear. But the engine is revving too slow for that lower gear, so the rear tire skids momentarily and the cycle jerks until the engine catches up to the wheel speed.


When riding with a semi-automatic clutch, remember to “blip” the throttle slightly to increase engine RPMs as you downshift. Click down with your heel to the next lower gear and slowly release the shift lever. You have just duplicated the process of downshifting a standard manual clutch.


The shifting process requires a short “learning curve” to become smooth as you work up and down through the gears with the semi-automatic transmission. The following tutorial by “Lazy Dog” is helpful to illustrate the process:

Riders who understand the operation of the semi-automatic clutch will enjoy smoother shifts.


It is possible to rapidly accelerate and “speed shift” into the higher gears. But rapid deceleration and downshifting will result in a jerky process and unnecessary gear and chain wear. Slowly release the heel shift lever as you downshift, as described above.


The heel-toe shift lever can be used to feather the clutch, just like a standard handlebar clutch lever. Pressing the shift lever slightly – BEFORE it clicks into the next lower gear – opens the clutch. That is, the internal gears are momentarily disengaged. Likewise, holding the shift lever down keeps the clutch disengaged. Until you release the shift lever, the next gear is not meshed with the engine. You can rev the engine without engaging the transmission, which could come in handy if you get stuck in the mud, sand, or on a slope.


I hope that you agree that there are MANY advantages to the semi-automatic transmission on the small 125cc motorcycles. In both town and trail riding, the motorcycle cannot be stalled! New riders simply ride away! With a little practice, experienced riders will adapt to not using the hand clutch. Both groups will enjoy smoother shifts as the pattern becomes second nature.

Understanding the operation of the semi-automatic clutch will also help eliminate one of the complaints about riding these small 125cc motorcycles offroad. There is simply ZERO power transferred to the drive chain until the engine reaches the mid-range in RPMs. You cannot crawl the bike at low RPMs – these small engines need to be ridden at higher RPMs and you need to shift accordingly.


This is not a concern of 90% of 125cc cycle riders. But if you plan on riding demanding trails, especially with a heavy rider or a heavy touring load, consider lowering the gear ratio (which requires changing the front engine sprocket to the next SMALLER size and/or the rear-wheel drive sprocket to the next LARGER size.) Lower gearing will result in higher engine RPMs and faster gear engagement at lower speeds, along with delivering more torque for climbing hills or moving more weight. This is just one of the customizations that CSC Motorcycles can perform, along with installing accessories, during the pre-delivery and set-up processes.

1 comentário

30 de jun.

You've got a typo: "From neutral, first gear is one click DOWN on the toe lever, followed by 2nd, 3rd, and 4th gears." Should read "one click UP" Cheers

bottom of page