Topic: CB750K3 primary chain slack

[junior]

My primary chain slack measurement is 66mm. I have read here on old threads that a new chain will measure 65mm. With replacement at 70mm I feel there is no need to replace it. Am I correct?  Thanks, Jr.   

[PeWe]

66mm is not much. No need to replace. Not hi milage, right?

Tensioner is ok too? Not turned hard and brittle leaving small rubber parts in the oil pan? Cam chain tensioner can do that too.

My K6 had 67.5mm slack when I restored it. It had done ca 40.000-45.000 km with 836cc, ported head and cam. Ca 75-80whp. Mostly long tours in high speeds.
Installed heavy duty chains when my plan was to increase the power.

[junior]

Thanks, PeWe for the response. No known history on this bike or motor. Bike is a K3 with a K4 motor. Tensioner wheel looks smooth and no bits on oil pump screen. Motor could be original and not rebuilt. In my minimal disassembly to evaluate, output shaft does show some wear on the spline and cam measurements are at below minimum, otherwise, it looks nice inside. I was able to run it up and down the road after getting it running. It ran, shifted, and idled nice for a bike that had tires date coded 2006 that looked new. Only doing a rider quality restoration so I might move on. Thanks again   JR.

[Don R]

 I have one that measures 70mm and you can hear the difference for sure.

[HondaMan]

I have one that measures 70mm and you can hear the difference for sure.

Yeah, what he said: ^^^
I have only ever seen 2 worn out to 70mm. One was well past 100k miles and the other was done in by rust after the engine sat in water 8" deep for 5 months, then was opened, cleaned out, reinstalled and run. The chains didn't last very long on that one.

Mississippi mud...nasty stuff!