Primary chain case alignment

gortnipper · Jul 30, 2020

Fast Eddie said:
I don’t like bending the studs, I really struggle how that can be accurate to a thou or two when using a BFH (Big F***ing Hammer)...! It also makes it a nightmare to remove the stair from the studs in future.

You are right, but you are wrong too.

You cant do it to a thou or two. But you can do it so that you can centralize the studs more to the holes.

And you dont need a BFH. The box end of a combination wrench over a doubled nut is plenty of leverage to do it judiciously.

olympus · Jul 30, 2020

Fast Eddie said:
I don’t like bending the studs, I really struggle how that can be accurate to a thou or two when using a BFH (Big F***ing Hammer)...! It also makes it a nightmare to remove the stair from the studs in future.

I prefer opening out the 3 mounting holes, if necessary (haven’t had to do it on my Commando though), then using some packing material to ensure perfect alignment as the mounting nuts are tightened.

It looks like you have a new stator there? My new stator was under sized, it would have been IMPOSSIBLE to get even the stock 10 thou clearance. I had the stator and rotor properly measured and the rotor turned down to suit. I actually doubled the clearance to 20 thou (40 thou under sized) and it works perfectly. Even with a carefully set 10 thou clearance I still had the rotor rubbing the stator (the bike gets revved hard), hence why I increased it.

My inner chain case is a snug fit on the crankcase spigot. So enlarging the three 1/4" holes would serve no purpose,
The centre stud isn't hardened so applying a slight set to it by gently bending and not clouding it with a hammer wouldn't be an issue.
Or as I did, open the hole through the cradle by one drill size size.
The issue of the stator misalignment is another matter... you want the spigots on the inner chain case and crankcase to be snug as possible as this is where the side loading is applied and not through those poxy 1/4" set screws.
My stator needed moving forward by several thou to achieve the rotor being mounted centrally and having a running clearance through its circumference.
For me opening the holes in the stator slightly was the obvious choice and using a cut up 4pt plastic milk container was the perfect shim

Fast Eddie · Jul 30, 2020

For clarities sake, the 3 mounting holes that I mentioned opening up were the holes in the stator. A milk carton wrapped around the rotor, as mentioned above, does a great job of centralising things whilst the nuts are tightened.

As above, there is no benefit to opening up the inner chain case holes.

Gortniper, BFH was a slight exaggeration I admit, but I still don’t like bending the studs IMHO, it may cause undue stress on things, and it will almost certainly make the stator a swine to remove (the buggers can be difficult enough at the best of times).

Heres a pic of my milk carton assembly (for clarities day once more, the milk carton is removed once the fasteners are tight...)

baz · Jul 30, 2020

Also when you set the air gap
Make sure you turn the engine and check the clearance in all positions of a clock
A bit more time/attention here will save lots of grief
Cheers

cliffa · Jul 30, 2020

Fast Eddie said:
For clarities sake, the 3 mounting holes that I mentioned opening up were the holes in the stator. A milk carton wrapped around the rotor, as mentioned above, does a great job of centralising things whilst the nuts are tightened.

As above, there is no benefit to opening up the inner chain case holes.

Gortniper, BFH was a slight exaggeration I admit, but I still don’t like bending the studs IMHO, it may cause undue stress on things, and it will almost certainly make the stator a swine to remove (the buggers can be difficult enough at the best of times).

Heres a pic of my milk carton assembly (for clarities day once more, the milk carton is removed once the fasteners are tight...)

View attachment 17908

Semi-skimmed obviously

Phliper00 · Jul 30, 2020

Fast Eddie said:
I don’t like bending the studs, I really struggle how that can be accurate to a thou or two when using a BFH (Big F***ing Hammer)...! It also makes it a nightmare to remove the stair from the studs in future.

I prefer opening out the 3 mounting holes, if necessary (haven’t had to do it on my Commando though), then using some packing material to ensure perfect alignment as the mounting nuts are tightened.

It looks like you have a new stator there? My new stator was under sized, it would have been IMPOSSIBLE to get even the stock 10 thou clearance. I had the stator and rotor properly measured and the rotor turned down to suit. I actually doubled the clearance to 20 thou (40 thou under sized) and it works perfectly. Even with a carefully set 10 thou clearance I still had the rotor rubbing the stator (the bike gets revved hard), hence why I increased it.

Yes I have a brand new stator. Is it possible to groove the inside of the stator to make the clearance ok? I have 0.010 at the 10 o'clock position, and 0.02 at the 3 position.

Craig · Jul 30, 2020

Phliper00 said:
Yes I have a brand new stator. Is it possible to groove the inside of the stator to make the clearance ok? I have 0.010 at the 10 o'clock position, and 0.02 at the 3 position.

Read above suggestions over again carefully ....

cliffa · Jul 30, 2020

Did you try fitting the inner case with the centre stud removed to see if the clearance is better? what happens when you rotate the engine, does it stay tight in the same area?

jbruney · Jul 30, 2020

When I had mine down replacing the counter sprocket/ tinkering w/ clutch plates, checking bearings, etc. I discovered it misaligned and the chain wearing into the case badly. After some clean up and fiddling I found the cure in a USS flat washer utilized as a spacer bringing it out to the perfect distance. Clearances remained good on everything else as good fortune followed me on the endeavor.
I believe this must have begun long ago with the PO because when replacing the triplex chain I found a connector link in it, so he had been inside the primary and clutch.... a few other items were moved about not worth mentioning which have been found out over the years also not done by me which caused little to no harm.

Phliper00 · Jul 30, 2020

cliffa said:
Did you try fitting the inner case with the centre stud removed to see if the clearance is better? what happens when you rotate the engine, does it stay tight in the same area?

this is exactly what i will do this afternoon. I think my inner case is not align perfectlyl...

olympus · Jul 30, 2020

When I first mounted up the rotor & stator (onto a new inner chain case) like a number of folk I found the rotor touched the stator. In my case at around 3-4 o clock area, but clearance around the remainder
I also mounted up the chain case supplied in my basket case, damaged/broken yes but the front spigot onto the crankcase was sound.... again the rotor and stator touched at around 14.00-16.00 area. So I rotated the inner chain case to prove a point, and the contact point moved as I rotated the chaincase.
This said to me that the stator stud locations were off...worrying on the new and the old case
I returned the case to supplier with photos, and it was replaced without question...
And the replacement case.... exactly the same as the one returned...

Fast Eddie · Jul 30, 2020

Phliper00 said:
Yes I have a brand new stator. Is it possible to groove the inside of the stator to make the clearance ok? I have 0.010 at the 10 o'clock position, and 0.02 at the 3 position.

Well, if you‘re correct, it’s impossible for you to get .010 clearance all round.

I don’t know if it’s ok to bore the stator out or not. As I posted above, I turned down the rotor.

cliffa · Jul 30, 2020

I wonder if a lot of these issues are because the case (for whatever reason) is not bolting up perpendicular to the crankshaft.

maylar · Jul 30, 2020

I have drilled the stator holes 1/64th inch bigger on mine.

marshg246 · Jul 30, 2020

Not sure if already mentioned:
1) I've found bikes with spacers of slightly different lengths. This causes the stator to be cocked and appear to be offset.
2) I've found inner covers where the surfaces that the spacers bear on are at slightly different levels - causes the same problem as 1).
3) I've found stators where someone tried to drill out the holes and forced the layers of metal apart with chips - makes a mess and can imitate 1)

It's difficult to tell if this is the problem, but if the feeler gauge slips in a bit but not all the way in, you should check several places to see if the stator is cocked. In some cases, moving the spacers around will solve that.

olympus · Jul 30, 2020

marshg246 said:
Not sure if already mentioned:
1) I've found bikes with spacers of slightly different lengths. This causes the stator to be cocked and appear to be offset.
2) I've found inner covers where the surfaces that the spacers bear on are at slightly different levels - causes the same problem as 1).
3) I've found stators where someone tried to drill out the holes and forced the layers of metal apart with chips - makes a mess and can imitate 1)

It's difficult to tell if this is the problem, but if the feeler gauge slips in a bit but not all the way in, you should check several places to see if the stator is cocked. In some cases, moving the spacers around will solve that.

Drilling the stator can cause this.. I clamped a piece of alloy plate over the top and drilled through it with a block of wood on the underside... to outer plates on the top & bottom still did splay out a little

cliffa · Jul 30, 2020

If the final resort is to drill the stator, it's probably best to drill only two of the holes, so it can "swing" on the un-drilled one. So for example in this case, leave the one at 11:00 o'clock as is and open the other two so it can be adjusted upwards and backwards slightly.

olympus · Jul 30, 2020

cliffa said:
If the final resort is to drill the stator, it's probably best to drill only two of the holes, so it can "swing" on the un-drilled one. So for example in this case, leave the one at 11:00 o'clock as is and open the other two so it can be adjusted upwards and backwards slightly.

I think the question needs to be asked why are so many of them like this???....
Can someone who has the primary stripped out and with the stator studs fitted, mount the inner case to the crankcase and nip up the three 1/4 set screws and then measure the distance on all three studs from the centre of the crank countersunk drilling to the stator suds... would be more accurate if someone had a cut down stud that had been centre drilled on the lathe. Then screwed in and the measurements taken.

Tornado · Jul 30, 2020

You might want to re-check the timing scale for accuracy on the outer cover once you're done fek'ing around with the inner fitting.

ILLF8ED · Jul 30, 2020

Fast Eddie said:
I don’t like bending the studs, I really struggle how that can be accurate to a thou or two when using a BFH (Big F***ing Hammer)...! It also makes it a nightmare to remove the stair from the studs in future.

I prefer opening out the 3 mounting holes, if necessary (haven’t had to do it on my Commando though), then using some packing material to ensure perfect alignment as the mounting nuts are tightened.

It looks like you have a new stator there? My new stator was under sized, it would have been IMPOSSIBLE to get even the stock 10 thou clearance. I had the stator and rotor properly measured and the rotor turned down to suit. I actually doubled the clearance to 20 thou (40 thou under sized) and it works perfectly. Even with a carefully set 10 thou clearance I still had the rotor rubbing the stator (the bike gets revved hard), hence why I increased it.

Nah, use an SFH....small hammer with light tap.

Primary chain case alignment

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