Primary Chain/Sprocket Wear

[BagONails]

Hi fellas, I've been doing a lot of searching and will be checking the service notes but I would welcome your views also if anyone in Australia can suggest any suitable suppliers here that would be helpful otherwise I guess I will be contacting SRM.

The weather here was lovely on the week-end and I went out for a second test run after getting the bike back together. After a few miles we stopped as I wanted to check battery charging with my voltmeter, (on board ammeter only registering negative). As suspected I don't seem to be getting any charge, battery voltage unchanged with revs but that no doubt will be another story... I then noticed red oil dripping from under the primary case. I had installed a fresh charge of ATF into the primary (185cc) previously so I was fairly sure where the oil was coming from. I turned for home cutting the ride short and dismantled the chaincase to have a look inside later in the afternoon.

Firstly I noticed the screws were quite loose and it did occur to me that perhaps I could have got away with just nipping them up and carrying on but as I had removed the exhaust, foot rest etc at that stage I decided it wouldn't do any harm to take a good look inside...I'm glad I did.

The p/o had mentioned he'd been running the primary dry with only a good coat of chain spray lube before heading out, I've no idea whether he'd changed the clutch bearing to a sealed one, I hope he has but now I think I will end up tearing it all down to see. The wear on the clutch chain wheel looks quite heavy to me and I think the primary has been adjusted to run too tight maybe to compensate or maybe the cause. The polished flanks on the chainwheel teeth may be result of chain being over tightened or possibly running out of line or both? I will investigate this. It looks like a new chain & sprockets required to my admittedly non-expert eyes tho.

The primary case joint gasket was a thick cork affair but this seems to have a crack in it. I'm thinking of cutting out a new .8mm paper gasket and dressing this with some non sealing Loctite gasket goo. Before I do this I will reassemble the cases and check around them with feelers and if I'm stripping the whole thing down I will clean up all the joint faces on a surface plate and some wet and dry. My searches have found various views on primary lube from a few squirts from an oil can will do to, the chain is seriously underrated and needs all the oil it can get...I was surprised to find only a single row chain behind there but hey it should do the job with decent lubrication so an oil bath seems to be appropriate.

Am I being over cautious with this amount of wear (the drive sprocket looks good by the way), is it normal to run these until there are no teeth left? Or is now the time to fit a new clutch chain wheel, drive sprocket and chain? see attached photos.  Many thanks in advance for your pearls of wisdom .

[RDfella]

That chainwheel is worn out - reminds me of rear wheel sprockets. Time for a new one I'm afraid.

[muskrat]

G'day BON.
The teeth aren't hooked so I think there's life in it yet. Definitely looks like a misalignment issue thou.
For a road bike it's best to run a wet primary especially with the std 6 spring.
Cheers

[WozzA]

Ian, I've got a good 6 spring clutch For Sale... PM sent if your interested..

[Colsbeeza]

Hi BON Ian,
A couple of ideas I have used for better oil sealing of the chaincase:- I assume your bike is a pre-unit.??
Mine is a standard set-up, and leaked like a sieve from around the gearbox shaft. I fitted an SRM-type felt ring over the clutch centre, which seals the gap. They sell them, but easy to make your own. Felt thickness of 2-3mm should do the trick. There are better ideas out there, but I wanted to keep it simple.
  When re-fitting the Chaincase Outer, I remove the Inner Case rear mounting bolt whilst fitting the Outer Case, to ensure the inner flexes to match the outer. Years ago I had originally found a noticeable gap between the cases around the middle and I had assumed that one or the other was badly warped. However, there had been no washers behind the rear bolt frame lug, and the inner bolt had flexed the inner cover to form a slightly concave gasket surface. The inner case is relatively thinner, and fairly flexible, but the outer is much more rigid.
 Secondly with rear bolt still removed (and making sure the gearbox bolts are tight after a rebuild -  I have attached the proper procedure to tighten the gearbox adjusting bolt to minimise tightening of primary chain), put gasket cement ( I used a firm setting variety) on the outer cover only and re-fit it tightly to the inner using all screws until the gasket cement sets - overnight. This to ensure the inner gasket surface is dead flat and the gasket cement is squashed evenly. Then remove it again and put a thin layer of thick grease (lithium?) on the inner face of the gasket and re-fit. Trying to do both in one go is messy and likely to get grease mixed with gasket cement, or displacement of the gasket.
So in the future you can remove it without tearing the gasket. I found that 0.8mm gasket material seals quite well.
Lastly re-fit the rear bolt and add the required thickness of washers behind the frame lug to ensure there is no load on the cases. It takes a little time, but satisfying.
Then add your 190mls chaincase oil.
Cheers Col
 

[Black Sheep]

P O did you a disservice. That looks like cruelty to the primary side. An unlubricated primary chain can/will destroy itself in 300 miles. These chaincases are not difficult to seal and once oiltight your primary chain and sprockets should last indefinitely. My A7 primary chain has now clocked up 60,000 miles and is still in good nick.

[BagONails]

P O did you a disservice. That looks like cruelty to the primary side. An unlubricated primary chain can/will destroy itself in 300 miles. These chaincases are not difficult to seal and once oiltight your primary chain and sprockets should last indefinitely. My A7 primary chain has now clocked up 60,000 miles and is still in good nick.

Hi Black Sheep, them's ma thoughts too! Although I think this chain wheel already had wear on it because the driving sprocket looks fine. I'll post a couple more photos later. I guess misalignment especially out of parallel would show more on the larger diameter. 

Hi BON Ian,
A couple of ideas I have used for better oil sealing of the chaincase:- I assume your bike is a pre-unit.??
Mine is a standard set-up, and leaked like a sieve from around the gearbox shaft. I fitted an SRM-type felt ring over the clutch centre, which seals the gap. They sell them, but easy to make your own. Felt thickness of 2-3mm should do the trick. There are better ideas out there, but I wanted to keep it simple.
  When re-fitting the Chaincase Outer, I remove the Inner Case rear mounting bolt whilst fitting the Outer Case, to ensure the inner flexes to match the outer. Years ago I had originally found a noticeable gap between the cases around the middle and I had assumed that one or the other was badly warped. However, there had been no washers behind the rear bolt frame lug, and the inner bolt had flexed the inner cover to form a slightly concave gasket surface. The inner case is relatively thinner, and fairly flexible, but the outer is much more rigid.
 Secondly with rear bolt still removed (and making sure the gearbox bolts are tight after a rebuild -  I have attached the proper procedure to tighten the gearbox adjusting bolt to minimise tightening of primary chain), put gasket cement ( I used a firm setting variety) on the outer cover only and re-fit it tightly to the inner using all screws until the gasket cement sets - overnight. This to ensure the inner gasket surface is dead flat and the gasket cement is squashed evenly. Then remove it again and put a thin layer of thick grease (lithium?) on the inner face of the gasket and re-fit. Trying to do both in one go is messy and likely to get grease mixed with gasket cement, or displacement of the gasket.
So in the future you can remove it without tearing the gasket. I found that 0.8mm gasket material seals quite well.
Lastly re-fit the rear bolt and add the required thickness of washers behind the frame lug to ensure there is no load on the cases. It takes a little time, but satisfying.
Then add your 190mls chaincase oil.
Cheers Col
 

Fantastic info Col, yes it is a pre unit A10. Thank you for your efforts setting all this out for me, between you and Swarfy (who PM'd me with a lot of good advice) I feel confident to tackle this, Cheers.

Ian, I've got a good 6 spring clutch For Sale... PM sent if your interested..

G'day WozzA, I got your message thanks. The clutch that is in there is the 4 spring one which I believe from what I've gleaned so far is generally held to be the best option so I will probably stick with it but will certainly keep your offer in mind. Thanks.

So the concensus seems to be if not entirely worn out it is well on the way so I will have to find a replacement and presumably a new chain. While I wait for the new parts I will tear it down and rebuild in line with your suggestions to ensure everything is lined up nicely and hopefully able to hold oil.  Thanks to all for your responses, you are a huge help. I'm a reasonable mechanic but have no experience on these machines, I can see its going to be an interesting journey...

[Swarfcut]

 I'd just add that the big nut on the end of the crank needs to be retightened to a gut busting 65 Ft/Lbs or thereabouts. The split pin solely serves to prevent a loose nut machining a hole in the primary case.  DIY custom peg spanner 43mm I/D or commercially available one is essential (Something along the lines of a Peugeot Ball Joint Tool?)...Not the hammer and chisel. That way you'll destroy the nut before it gets anywhere tight enough. All covered in previous Forum Posts. SRM market a replacement nut with a conventional hex drive.

 Swarfy.

[Black Sheep]

Some dreadful bodgers use a big stilson with a length of pipe on the handle..

[Colsbeeza]

Ian,
Re:  "Although I think this chain wheel already had wear on it because the driving sprocket looks fine".
In my experience, the rear sprocket - either clutch or rear wheel always wear much faster when something is not right like no oil. Once the chain wears, it lengthens ( we used to call it stretch) and the rollers begin to ride up on the teeth simply because there are many more of them - like 43, causing abrasion as the rollers ride up and down the faces of the teeth. When the chain enters tooth 1, then a roller might be riding atop tooth 40.
With engine sprockets and gearbox sprockets, only 18-22 teeth so the sprockets can accommodate the "stretch" a little better without riding up on the teeth. Does that make sense?
When I was a teenager with no money or brains, I would wear the rear sprocket on my bush bikes so badly that the chain would ride over the teeth eventually snapping off the tips of the teeth and losing all grip. Who bothered to clean and oil the chain when having so much fun.? I could guarantee 3 rear sprockets for each gearbox sprocket purchased back then.
Col

[BagONails]

Ian,
Re:  "Although I think this chain wheel already had wear on it because the driving sprocket looks fine".
In my experience, the rear sprocket - either clutch or rear wheel always wear much faster when something is not right like no oil.
Col

I don't know the exact wear mechanisms involved Col, your theory sounds as good as any I've heard but put simply I think we can say without fear of overstatement...'its carked it!'  Looking at the driver now there is a fair bit of wear there too so it looks like a full house replacement job plus realignment etc. See attached piccies.

Some dreadful bodgers use a big stilson with a length of pipe on the handle..

It is terrible what some people get up to, of course nobody on here would stoop to such lows...

I'd just add that the big nut on the end of the crank needs to be retightened to a gut busting 65 Ft/Lbs or thereabouts. The split pin solely serves to prevent a loose nut machining a hole in the primary case.
 Swarfy.

That's 88Nm in new money, my car's wheel nuts go to 135Nm so that doesn't sound too bad but the nut design makes it a challenge for sure, will need to lock everything up no doubt. I can't see a split pin in my photo....hopefully there is one in there somewhere, at least those two hex screws are drilled & wired!

My A7 primary chain has now clocked up 60,000 miles and is still in good nick.

That's it once I get this show on the road I want at least another 60,000 miles out of it   

Once again I really appreciate your thoughts guys, cheers.

[RDfella]

"An unlubricated primary chain can/will destroy itself in 300 miles". I just love these assertions. I haven't put oil in a primary case (apart from Villiers, where the cork clutch requires some oil) in 50 yrs. Done many thousands of miles since then and yet to have a primary fail or wear out.

[Minto]

"An unlubricated primary chain can/will destroy itself in 300 miles". I just love these assertions. I haven't put oil in a primary case (apart from Villiers, where the cork clutch requires some oil) in 50 yrs. Done many thousands of miles since then and yet to have a primary fail or wear out.

I'd love to try out this theory, but I can guarantee I'd forget to spray lube through the hole and kill it within a week.
But the lure of a dry primary, oh I can but dream.

[BagONails]

"An unlubricated primary chain can/will destroy itself in 300 miles". I just love these assertions. I haven't put oil in a primary case (apart from Villiers, where the cork clutch requires some oil) in 50 yrs. Done many thousands of miles since then and yet to have a primary fail or wear out.

I'd love to try out this theory, but I can guarantee I'd forget to spray lube through the hole and kill it within a week.
But the lure of a dry primary, oh I can but dream.

Oh no RD! Look what you've done, its happening, its turning into one of those lubrication threads 

I was once told something that has served me very well in life:
"a bit of lube makes everything better" 

Cheers Bagger

[Colsbeeza]

Ian BoN,
Re: "That's 88Nm in new money" - I believe that the 65 ft-lbs torque (88Nm) doesn't all get transmitted to the crank nut. I think the ramps on the cush change the force vector by something like a 30 degree angle at point of tightening and push back against the tension wrench. So your 65 is probably not exceeding about 45 ft-lbs on the nut, with the remaining 20ft-lbs on the ramp. Although I have got the tools to lock clutch sprocket etc, I have changed my thinking and moved on to using a rattle gun / impact driver like Muskrat does. Mine has a max of 100 Nm, and is a cheapy from Ryobi. This also puts no forces on the clutch housing or bearings or primary chain (which I had calculated some time ago to about 130Kg force). Many will not agree, but that is IMHO.
Col