Aprilia RS125 Rotax 122 balancer Shaft Timing/Markings

[supra3turbo]

Hi All,

I am getting this spare engine back together, and the book says one thing, and ive seen people online do it differently, which is the correct way?

I have noticed in the manual it says to align the marks on the ends of the crank shaft and the balancer shaft exactly (1) with each other, but this engine was assembled with just the outer gear teeth markings (2) aligning, which one is correct? The haynes manual shows to align both shaft end marks (1) exactly, but if i do that, the teeth markings (2) dont align at all, and the manual makes no mention of the outer gear teeth markings. Do i align the shaft markings, or the teeth markings.

Thanks - joe
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Hoda CBR 600 FX stolen from stalybridge 2017/2018 black
Current Project Suzuki RG125 Cafe Racer

[jaffa90]

https://www.youtube.com/watch?v=U4md9VkpAKk&t=2242s
Is this yours? This has markings on both shafts and both inner parts of the plastic gears, then you line up the outer parts of both plastic gears.

[supra3turbo]

[jaffa90]

This pic may help as well.

[jeffyjeff]

Are the gears are indexed to the shafts so that they only fit in one position? There may be a missing or dissimilar spline on the shaft and the gear that allow the gear to mate with the shaft in only one orientation. If that be the case, I would be inclined to trust the gear marks as I assemble the engine.

If the gears are not indexed to the shafts, then the orientation of the gear marks in relation to crank position is totally random. Your photograph appears to show 16 teeth on the splined shaft (secured by the snap ring). That suggests the gear can go on the shaft 16 different ways, only one is the correct position. If that indeed be the case, I would be inclined to prioritize the marks on the shafts.

Bottom line is that when the crankshaft is turned to position the piston at top-dead-center (the uppermost of it's vertical travel) you must be able to orient the camshaft so that the tappets ride on the base of the camshaft (not the nose of either cam). That would be the point where you can set the valve lash, and that is the point where your timing marks should align.
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History shows again and again how nature points out the folly of men - BOC

[jaffa90]

jeffyjeff, it`s coming up as a 2 stroke engine not 4.

[supra3turbo]

Hi all,

I've had it confirmed, you line the gears up on the shafts then line the teeth marks up together, odd that Haynes don't show that but apparently that's correct.

Thanks for the help
____________________
Hoda CBR 600 FX stolen from stalybridge 2017/2018 black
Current Project Suzuki RG125 Cafe Racer

[jeffyjeff]