Camchain and tensioner seen up close in a cutaway bike engine

Home Repair And Restoration

Honda Camchain Tensioner Test

Video Date - 25 April 2016

By Ren Withnell

The camchain tensioner on my CBF 125 and many of the other recent Hondas is a simple affair consisting of a coiled spring on a threaded plunger. If you have reason to doubt the tensioner then checking it for diagnosis is quite simple.

From the video you can see there is a cover that can be removed. Beneath this there is nothing obvious but deeper within the mechanism there is a slot. This slot can be turned using a watchmaker's screwdriver - flat tip. By turning the slot we can tighten or loosen the tension on the tensioner blade. If we loosen the tensioner we will hear the cam chain start to rattle a lot, if we tighten it the rattling should stop. 

NOTE!!!! Only turn the screwdriver a little. If you turn it a lot you risk making the cam chain so loose it jumps some teeth. This...THIS will DESTROY your engine!

So - if you bike has a suspected cam chain rattle - tighten the tensioner using the screwdriver in the slot. If the rattling stops then either your tensioner is suspect or the cam chain itself. If however it makes no difference when you tighten it and you hear another rattle as you loosen it then it is unlikely to be a cam chain rattle. Simples!

Ren's hand ahdjusting and checking the cam chain tensioner

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