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Engine Repair Videos

These videos have been checked over by our Thumpstar mechanics

How to adjust your tappets

In this how to video, we are showing you the process for correctly adjusting the engine tappets.

How To Set Cam Timing

Step by step guide in how to set the cam timing for horizontal engines.


Guide in replacing the stator plate on a 110cc pit bike

Gear leaver, YX, GPX, Zongshen

Information on different kinds of Gear Leavers with measurements.

Engines, Zongshen, Lifan, YX, GPX Information

Lifan 88cc – are normal good from 55cc to 125cc. Only used on smaller bikes. Engine mount measurements (universal engine mount/CRF50): eye to eye between the top and bottom mount: 152mm; top mount is 93mm and bottom mount is 82mm; Bolt is 8mm; Length of this motor: from the very top to the back engine mount is about 425mm and the width is about 28cm.
YX 125 – 4 speed motor. Also known as a 125 GPX. It’s a neutral start. You would have to put it back to neutral, make sure the clutch is out and kick it over. They have the 5-pin green plug CDI’s.
Zongshen 155 – Also known as a 160. It has a wider KLX-based head which is about 18cm. CDI wiring for Zongshen has an 8-pin dice plug.
Daytona – the Japanese motor which is expensive. It is a really good brand. They have removable oil filters in them like the Zongshen.
Electric Start semi-automatic 110cc motor – 4 speed doesn’t need a clutch. Pressing a button starts it. You can get the side covers to look like the manual engines.
Zongshen 140 – A common motor and same engine mounts as the other ones. It has the same black box CDI. You could identify this easily by seeing the series of numbers (the top number is the actual engine number and the bottom number is the custom number that’s different for every single motor).

Kick Start Information

Information on Kick Starts.

Dress Up Kits and Cam Covers Information

CRF head based dress up (CRF Honda)

Engine Oil Cooler Information

Generally it is not recommended, unless you need oil coolers for racing. If you put it on a 125 cc below models, you would need to have an adapter (two holes on it). The ten mill lines will be clamped on to the engine and you’re good to go. Ten ten mill lines is put on the mount in points and is not expensive.
Two lines to choose from (ten mill and eight mill). Zonghsen and Lifen use the ten mill.