TOPIC:

IWe all know that the camshafts is not driven directly from the crankshaft, but from the secondary shaft, which itselv is driven from the crankshaft by the primary chain. Now I really cannot understand why the crankshaft and secondary shaft should be timed together as described in the service manual page 109. I have of course followed the description, but as said don't understand it. I might be overlooking something important, but as I see it ,the only thing that matters is the relationship between the crankshaft and the camshafts. The secondary shaft is just a round shaft and how it is placed in relation to the crankshaft can have no importance, or has it ?
I feel a little dumb, but hopefully somebody here more clever than me can explain it ???

As far as I know, it has to do with smooth gear changing. Best position of the dogs engaging gears in correlation to the position of the crankshaft so the forces will allow for smoothest transition.

StanG wrote: As far as I know, it has to do with smooth gear changing. Best position of the dogs engaging gears in correlation to the position of the crankshaft so the forces will allow for smoothest transition.

I have not thought on that possible purpose. All the time I have been thinking on the relationship to the camshafts. But if it has something to do with smooth gearchanging, I would think that not only the primary chain but also the secondary chain driving the front gearbox shaft should be timed with marks on the sprockets, and this is not the case.

That was my initial reaction as well, but that's what I read without further investigating and I'm just passing it on. I can't recall where I read it right now.

I have an update to this question. So, it is related to the smooth gearing at the end, but not directly as it would be if the secondary chain was also timed in a similar way as well.

What happens is the crankshaft and the secondary shaft must be balanced for smooth transition of power, and the chain acts as a balancer once both are timed correctly. The secondary shaft needs to be positioned (timed) correctly in relation to where the pistons are. Not being balanced would also affect the gear changes. But that's not the biggest problem but rather an aftereffect. Without being balanced correctly, the engine would shake and eventually fall apart. That's the real danger and the reason for timing them. When everything is smooth at the secondary shaft, all that's behind (the gearbox) will work smooth as well.

That is it, unless anyone has something to add.

Cheers!
Stan

The secondary shaft.

Thanks a lot Stan for clearing up this mystery