Starter confusion

[chrisk]

All right, I admit deafeat. Using bearing: 25x32x20 in the starter chainwheel, which has a depth of 29mm what takes up the other 9mm?) the sealing surface of the gear is 10mm wide, what stops the chainwheel moving toward the crank bearing? It's like there should be a spacer or the like. I can push the chainwheel towards the crank bearing until the seal drops into the step between the seal surface and the side of the sprocket.  Good grief, I just read that, and near confused myself!

Here's how the chainwheel should run, seal on mating surface.

Then, what stops th chainwheel from pushing in toward the crank bearing, like this? The seal mating surface has past the seal, and the seal is now within the stepdown.

And then there's this little issue: 25x32x20 needle bearing with a 9mm free space.

 

[sfcpiet]

Stop thinking about it and stuff it back together.  Don't forget the oil seal.

The wheel has a lot of side clearance, it centres itself when in use and the large crankcase oil seal stops it from moving around when the engine is running.  If it does tend to wander/tilt with the engine running, your crank is mis-aligned.

piet

 

[Tippie]

I understand your worry Chris. I just checked a motor I have here and the mating surface is on the seal, not past it like on yours. Like Piet says it might not matter, but you will be relying on the chain to hold it in position and not fall in past the seal. The needle bearing is pressed all the way in, so it sits centred under the sprocket itself on that motor also. Assemble the whole lot and see how it all lines up.

 

[chrisk]

Thank fellas, I'm not a mechanic or an engineer, but, man that just frys my brain. The bloody thing just floats around wherever it wishes....... But then, I suppose they've been floating around for over 40 years and if it's ok with you blokes, who know better than me, I'll take your word that it works.

Maybe the inside edge of the sprag clutch needs a few of those rare earth magnets implanted into it just to help the sucker stay put....... But, then, I'm not a mechanic.

 

[Dellortoman]

Floating around on the shaft like that just seems wrong to me. I reckon I'd be tempted to make up a spacer.

 

[Paul Marx]

That is too much.
Wheel more or less abuts on the crank roller.
Paul

 

[piranha-bro2]

Chris
If it's a double lip seal, it may go beyond the outer dust-lip. As long as it has plenty of side-to-side clearance once the starter clutch is fitted and FULLY tightened, you have no probs. I know what you mean, and I will press the main seal in a little to achieve a guaranteed seal on bot lips of the seal.

I once made the fatal error of fitting a new starter clutch without allowing freeplay and it spun the starter motor and destroyed it.

Pic here of an SF motor I have in the garage ...