market dynamics
Pedal motorcycle fuel consumption is high, variable speed system working condition influence is also very big, see this example!
Release date:2020.11.17

Scooter fuel consumption, many friends are the first suspect is the carburetor, think is adjusted improperly, or there is a blockage, some master will only wash or replace the carburetor, but there are many reasons for this situation, today we will introduce a different, for everyone to do a reference.

A CL50QT scooter, as shown in Figure 1, traveled more than 56,000 kilometers. Due to the decrease of the maximum speed once, the user changed the transmission components in the repair shop. The little apprentice operated carelessly and pulled the M10 thread on the left side of the crankshaft assembly, which could not be repaired.

After the replacement of the crankshaft component, the maintenance station reported that the fuel consumption of the car increased gradually and the maximum speed could not reach the original 50km/h. The maintenance workers checked the electric, oil and gas lines respectively, but found no abnormalities, and the cause of the fault was unknown.

Maintenance worker review failure: start the engine, warm the car more than 10 minutes on the road, the maximum speed is only about 40 kilometers.

Stop the car and open the fuel tank cover to check that the air vent is not blocked. Remove cylinder block and piston, check the elasticity of piston ring, basically normal. No abnormal wear on cylinder cylinder and piston skirt.

Remove the left side cover, decompose transmission, clutch, triangle tooth belt and other transmission mechanisms found that the triangle tooth belt abnormal wear phenomenon, the belt width has been from the original 15.5mm thin to the current 13mm, the left cover is full of tooth belt wear black rubber powder.

Ask motorcycle user, from the last repair and replacement of crankshaft so far, just drive less than 1000 kilometers, transmission, clutch and gear belt are replaced together the original factory accessories, there is no fake and inferior products, should not occur in such a short period of time serious wear.


But, can not find the specific reason of abnormal wear and tear, had to change the tooth shape belt first.

In the assembly process, it was found that there was an obvious gap between the 15° chamfered surface on both sides of the gear belt and the transmission bevel. Careful inspection of the straightness of the gear belt at the transmission end and the clutch end showed that the result was not in a straight line, and the gear belt was obviously to the left at the crankshaft end.

Ask the user that the original transmission mechanism has been normal use, found no abnormal situation, only after the replacement of the crankshaft components occurred.

Decomposition engine, crankshaft component, depth vernier caliper is used to measure the fault engine crankshaft installation chuck of gearbox Φ 15.6 mm face to crank arm plane, the distance of 48.5 mm measured crankshaft corresponding normal size only 46 mm.

In this way, the left end face of the fault crankshaft shifted 2.5mm to the left, making the operational center of the gear belt deviate from the center line of the transmission and clutch, resulting in abnormal wear of the bevel of the gear belt.

When the wear exceeds the use limit, the speed ratio of the transmission mechanism changes, so that the fuel consumption gradually increases, and the maximum speed does not go up.

Replace the authentic crankshaft component (see figure 2) and the triangular tooth belt, check the toothed belt on the transmission and clutch the straightness (as shown in figure 3) basic normal, complex engine, start the vehicle on the road, accelerate to feel good and top speed of 50 km, tracking user three about more than 2000 kilometers, motorcycle use basic normal, fuel consumption also restore the original state of normal, confirm the original car fuel consumption big fault be ruled out completely.