Primary chain alignment

How to align sprockets for primary?

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Sarre
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Primary chain alignment

#1

Post by Sarre » Sun Aug 11, 2019 3:53 pm

Have checked the books and knowledge base, googled, but no info (besides a lot of info on belts). On the other hand maybe there is nothing wrong?

First pic is the setup, its a tsubaki primary chain. I've tried to get the angle right on photos 2 and 3 to show the offset between both sprockets, I use the primary to judge the alignment on. Is that the right method? Is it even out of alignment? It "seems" that the sprockets grab the chain fine but that's of course in slowmo.

What are the options?
- Move engine inwards?
- Move transmission outwards? Don't expect that much clearance though..
- Shimming the transmission clutch hub?
- Is the engine sprocket far enough up the shaft?

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Re: Primary chain alignment

#2

Post by panhead » Sun Aug 11, 2019 4:17 pm

- Is the engine sprocket far enough up the shaft?
Looking at the nut I would say no.

RooDog
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Re: Primary chain alignment

#3

Post by RooDog » Sun Aug 11, 2019 5:44 pm

Eye balling the chain run by the tin primary is not valid. With no chain in place a straight edge seated on the motor sprocket could indicate where the chain runs and meets the clutch drum sprockets. This looks to be a tapered motor shaft and there is no way to relocate that engine sprocket, but the clutch shell may be adjusted slightly by varying the thickness of the thrust disc riveted to the base of the clutch hub, OK? Also, the reason there is info in belt drive alignment is that it is critical for a belt application, a double row chain is much less sensitive to miss alignment, both for lateral, and for parallelism of the two shafts involved.
...RooDog....

Sarre
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Re: Primary chain alignment

#4

Post by Sarre » Sun Aug 11, 2019 7:59 pm

RooDog wrote:
Sun Aug 11, 2019 5:44 pm
With no chain in place a straight edge seated on the motor sprocket could indicate where the chain runs and meets the clutch drum sprockets.
Have done it, the transmission is 7mm inwards compared to the engine sprocket.
RooDog wrote:
Sun Aug 11, 2019 5:44 pm
This looks to be a tapered motor shaft and there is no way to relocate that engine sprocket, but the clutch shell may be adjusted slightly by varying the thickness of the thrust disc riveted to the base of the clutch hub, OK?
Taper yes, ‘50. Not exactly clear to me about the thrust disc. Is 7mm achievable?
panhead wrote:
Sun Aug 11, 2019 4:17 pm
- Is the engine sprocket far enough up the shaft?
Looking at the nut I would say no.
That was my thought as well, the sprocket looks new, the nut is new, it should go up further, but not 7mm.. I removed the sprocket and the key, without key it won’t go up further either.. The new nut is slightly thicker compared to the old nut. There is no damage to the tapered shaft, nor to the inner taper of the sprocket.

The question about how the shaft should meet the nut was already asked but never answered. :)

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Re: Primary chain alignment

#5

Post by RooDog » Sun Aug 11, 2019 9:13 pm

7mm is more that a 1/4" to us 'Mericans. Something is way off.
BTW: My motor sprocket nut with a Super Max front pulley fits the same as yours. I was also going to suggest leaving out the woodruff key, some times they are the wrong size and bind, but you have also done that. The thrust disc, riveted to the clutch hub, is a lot thinner than what we are dealing with here, like maybe 3-4mm, so I'm tossing that idea too. If you had an electric start transmission main shaft the clutch would be too far outward, that is not the case here, but you do have an E-start clutch shell; see where it is relief machined for the starter ring gear, again that should not affect anything.
Lo siento. I have no idea where the problem lies....
Best Wishes.....
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Larry
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Re: Primary chain alignment

#6

Post by Larry » Sun Aug 11, 2019 11:53 pm

There were some engine sprockets made with the wrong taper. Can't be used. Check yours.

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Re: Primary chain alignment

#7

Post by Andygears » Mon Aug 12, 2019 11:43 pm

Larry wrote:
Sun Aug 11, 2019 11:53 pm
There were some engine sprockets made with the wrong taper. Can't be used. Check yours.
I think Larry may have it, take off the engine nut and take a close up of the sprocket seated on the shaft with no key. Maybe we can judge by how much sprocket taper bore is showing comparing it to a known correct sprocket.

My two cents
Andygears

Sarre
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Re: Primary chain alignment

#8

Post by Sarre » Tue Aug 13, 2019 7:49 pm

I've put some lapping component on the taper and spun the sprocket, the "untouched" surface of the sprocket is about 5mm. (3/16 to 13/64) That means that by putting pressure on the sprocket with the nut it should move up the taper that 5mm for full contact, which is a lot I guess? Supporting the hypotheses of Larry and Rubone (in a similar topic as this one). See pic.

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