market dynamics
Motorcycle repair story: why is it so difficult to shift gears on this motorcycle?
Release date:2020.05.12

A cl125-3 chunlan tiger motorcycle, travel more than 36,000 kilometers, there is abnormal sound of gear operation in the crankcase, the user is a car driver, a little mechanical knowledge, self-decomposition of the engine, replace the damaged gear.

Due to unskilled operation, the special bolt of the stop used to tighten the gear shifting mechanism is lost. In desperation, according to the relevant size of the stop and the thread on the right crankcase, a new special bolt.

It was found that the engine was difficult to shift gears in both cold and hot engine conditions, so the user could not troubleshoot the engine and pushed the car to the maintenance station for inspection.

Motorcycle shift difficulty is composed of many factors, considering that the car is being replaced by change gear, whether in the replacement of crankshaft speed parts when loading or defective parts for replacement of special circumstances, such as mechanic decomposition engine again, remove the crankcase, to change gear, fork and examined shifting all institutions, all did not find the point of failure.

Had to change gear and shift to the crankcase institutions after loading (install) of crankshaft temporarily not, will be a common M6 bolts on the shift CAM Ф 6.5 mm hole to screw into the shift drum gear screw and screw down the, use the socket wrench CAM and shift gears drum rotating shift back and forth, starting from the low which is 1-0-2-3-4-5, and then in turn from high-grade or 5-4-3-2-0-1, not found any dull and difficult phenomenon to change gear.

After closing the box, install the fastening shift CAM, and use the hexagon sleeve repeatedly turn the shift gear drum, there is no abnormal phenomenon. There is no problem with the transmission and shift mechanism in the crankcase.

Fault should be out on the shift CAM and stop, take a start-stop actuator look carefully, stop roller is very flexible, didn't find any abnormal situation, by the way, will stop fastening bolt to stop about Ф 9 mm hole, found that after the bolt insertion hole stop, can't free activities.

Use vernier caliper to measure the relevant sizes, the cause of the failure is shifting stop fixed aperture for 9 mm, cooperate with the special dedicated Ф 9 mm, bolt diameter and the outer circle is not round, the fit clearance is too small.

Again carefully measure the special special bolts and shift stop found, the steps of the bench height and thickness of the stop basic consistent, not only make homemade special bolt and shift stop fixed basic no clearance hole, and after the retaining bolt fastening, stop tightly pressed in special special bolts on the steps, seriously hindered the normal shift stop swinging, lead to a difficult shift, the original fault point here.

Maintenance workers from a scrapped chunlan tiger car engine to remove the gear CAM fastening with a special bolt, and the original car gear shift stop was successfully tested, the special bolt and gear shift stop radial clearance and axial clearance, are in the appropriate range.


Carefully assemble the parts and components, from 1→0→2→3→4→5, and then from 5→4→3→2→0→1, carry out gear shift, all activities freely, start the engine, in the state of heat engine shift back to normal, confirm that the original car is completely removed from the difficult gear shift fault.