Chain clearance

[Craigy]

Hi guys,
Is there a way to move the drive chain away from the rear of the primary case? A10 swinging arm

I’ve not not noticed before but mine is either touching or very close.

I’ve just added an extra steel plate to the clutch as mine only had 5 plates, not the 6 as listed, but assume this would make any difference to the rear/outside the casing

Cheers Craig

[limeyrob]

Is the spacer installed between the chain case and the crankcase and is the bolt at the rear of the chain case to the frame set right?
I would also check the gearbox sprocket is correct and tight.

[chaterlea25]

Hi Craig,
There's not a lot of space there at the best of times
Some brands of chain and H or O ring types are wide enough to foul the chain case
Plus what Rob wrote

John

[Swarfcut]

  CJ deserves an accolade  here for an epic explanation of primary chain alignment and problems with aftermarket clutch to mainshaft adaptors, all on the Forum somewhere. It is very extensive and will help get things sorted.

 But start with the simple stuff.... twisted or bent inner primary casing, gearbox mountings, position of components within the frame, worn inserts to the 6 spring type chainwheel, along with wear to the centre fingers of the thick circular plate behind it. That adaptor, a whole load of bad ones appeared a while ago, wrong taper along with scrolls turning the wrong way, too thick a crankcase spacer plate,(actually unnecessary if no rear chaincase is fitted). No doubt other folks can add a few more.

 From experience the inner chaincase rear mount can end up close to or well away from the frame lug.  Don't strain the case to the frame, use a custom spacer to bridge the gap so everything is secured with no strain on the inner chaincase.

 Swarfy.

[Craigy]

Hi Swarfy,

Thanks for the info. I’ve had a look and think this is what you mentioned.

https://www.a7a10.net/forum/index.php?topic=9646.0

It seems that this is mainly concerning Primary Case gears. My issue is the main drive sprocket behind the primary case. The drive chain is either hitting on the rear of the primary case or very very close.

I’ve been wondering…..you will recall I had an issue with the clutch plates/clutch ID. I now know it’s a 4 spring Triumph clutch, I added an extra steel plate as it only had 5 instead of 6.

Do you think this could have had any effect on clearance at the rear of the casing?

I’m new to all of this, I don’t know if the clutch plate thickness could do this. It’s just a thought, 3mm extra in the plates and the main sprocket is pulled closer to the casing.

What’s your thoughts.

Cheers Craig

[limeyrob]

You could put a 2nd spacer plate between the engine and inner chain-case and that would move it all over by about 1/8". 42-7518.  If you do get it all straight then put washers in the rear bolt 64-6054 so its just right, no strain.
I happen to have one for sale on e-bay at the moment for £9 

[muskrat]

G'day Craig.
As john said the chain normally does run very close to the back of the inner primary especially heavy duty chains. A standard chain will handle the massive power of an A10 (what I ran on my racer). The clutch will play no part of the issue.
Check that the motor and g/box are in perfect alignment and the rear wheel is straight in the swingarm/frame.
Cheers

[limeyrob]

I'm thinking out loud here, the final drive nut could be loose, unlikely but worth checking its 67-3053 and has a tab washer 24-4263

[chaterlea25]

Hi Craigy,
Are you sure the gearbox sprocket nut is tight? Then its back to the chain type and width question?
What thickness of spacer or washers are between the rear of the primary case and frame?
What distance is there between the primary chain and the inside of the rear case?
The primary chain must not be a H type or cheapo wider type, Renolds / Regina are the narrowest width wise nothing else will really do
Believe it or not the inner cases are quite flexible and easily distorted, high spots on the rear face happens from many tightenings of the wire locked bolts.  The high spots can be carefully pressed back down and then dressed flat..

John

[Craigy]

Hey guys,

Thanks for the replies and info. I’ve been studying what has been said and really wish I had the knowledge and confidence to pull the gearbox out, but looking at options before I end up I’m bigger strife than I already am.

Limeyrob, I assume the only way to get to the sprocket nut is with gearbox removal, and certainly to get an extra spacer in there it would be required. Looking at the exposed diagram, it looks like the sprocket is on a ‘machined collar’. If this is the case, how does this go with moving the sprocket towards the gearbox casing? Is this not a predetermined distance to marry up with the shaft? If it is a case of moving the sprocket away from the rear of inner primary case and the gearbox spacing remains constant, does this push the primary case outwards, affecting the alignment of the clutch/primary chain/casing?

I’m really confused by this, as I said without the knowledge it’s hard to take the leap of removing the gearbox.

I have removed the rear wheel, loosened everything off etc, it’s pretty obvious that wheel alignment plays no part in this, as I was hoping, the distance between the sprocket and the chain hitting the casing is close so it has very little opportunity to move away from the casing.

I have checked the chain, it’s a standard chain, so no movement there.

Cheers Craig

[Swarfcut]

 To be honest, problems with chain alignment are more to do with the primary, so an error there on my part in "not reading the question"

 Drive chain alignment is fixed by the position of the gearbox. We assume frame and mounting plates are as they should be. The main gearbox output bearing is pressed into the gearbox casing from the outside, then on goes a flanged oilseal and  a retaining circlip.

 The gearbox sprocket has that "machined collar," which runs on the oilseal. Finally a circular nut with a tab washer clamps the drive sleeve, bearing inner and sprocket together. Located by the circlip, this ensemble is therefore fixed relative to the rest of the machine. Rogue parts and incorrect assembly are all possible, particularly the gearbox sprocket being too thick. You may find the circlip missing and the bearing moving out of the gearbox casing towards the back of the primary case. Rob's thought on the tightness or otherwise of the sprocket nut is worth a first look, as is checking for in/out movement of the gearbox sprocket....there should be none. You can check the bearing by feel, the sprocket and drive sleeve assembly should rotate smoothly, with no lift, shake or axial movement.

 If all is in order it is time to check the inner primary case for bend or twist, and the state of the circular spacer between the crankcase and inner case. Moving the chaincase away from the gearbox compromises the primary chain clearance behind the clutch, so here comes another problem...

 Swarfy.

[muskrat]

G'day Craig.
To get to the sprocket nut the primary has to come off (clutch, chain, outer & inner cover). While it's all off check the motor/gearbox alignment as when adjusting the primary chain the g/box can be twisted in the plates (the adjuster pulls on one side and can cock it off). Throw the clutch on and use a straight edge between engine sprocket and clutch chain wheel. To get it perfect you may need to loosen the engine mounts as well. Once it all lines up and mounting bolts are tight check it again with the straight edge. Once satisfied rip the clutch back off and install the inner primary. How is the clearance now?
Cheers

[TimK]

I have checked the chain, it’s a standard chain, so no movement there.

Cheers Craig

Hi Craig
Although you say the chain is standard, modern standard chains are a lot wider than ones made 60+ years ago even if they're not fitted with O rings. Renolds make a Classic chain that is suited to the limited space available around the final drive sprocket on an A10. See if a local friendly shop will let you measure one which you can then compare with your current chain.
Cheers
TimK

[Craigy]

Hi Tim, I’m in darkest Adelaide so doubt I’d get a chain to measure. 🤔.

I’m down to the shaft inside the primary case, just need to buy a puller tomorrow to try to get the sleeve off it.

I know there’s about 1/8” movement on the sprocket behind the gearbox so hoping a washer/shim will take up the play and keep the sprocket away from the primary case

[chaterlea25]

Hi Craig,
OK, it sounds like the sprocket "nut" is loose allowing the sprocket to move outwards
Measure the chain width (pins) and I  can compare with what I have here, I have a selection that I'm hoarding
Depending on which clutch you have they are threaded for special puller, not easy to remove if they were properly tightened.
I made a tool from a piece of steel tube to fit the slots in the sprocket nut, can be made with a hacksaw and drill a hole across for a Tommy bar to tighten, add loctite retainer to degreased threads
The crank and clutch nuts need to be tightened to 65ft/lbs and I use retaining compound on these too

John