Sprag starter noise resolved......kinda (2010)

Gidday. I think i have finally resolved the horrible grinding , gnashing noise when from inside the primary when I hit the starter and the deep knocking noise at low revs when I blip the throttle. firstly the grinding noise was from some lateral movement in the anti backfire device. seems there was some wear in the bush in the inner cover allowing the anti device to move inwards towards the inner cover and the gears on the device were contacting the stainless steel plate that supports the hydraulic chain tensioner. I placed a couple of washers in the bush housing and this seems to have solved it.

The deep knocking noise is the 2 hydraulic chain tensioners bottoming out in their housings. When I blip the throttle you can see / hear them doing this. I have no idea why.

Questions.
1) Why have they decided to do this? I primed them with oil, which leaks out anyway thru the tiny holes. Will they self prime as time goes by? The other question is why do they not do this when the clutch plates are removed? something to do with load perhaps. New ones are $180AUD. would like to avoid the expense.

cheers Hiilbone

hillbone said:

Gidday. I think i have finally resolved the horrible grinding , gnashing noise when from inside the primary when I hit the starter and the deep knocking noise at low revs when I blip the throttle. firstly the grinding noise was from some lateral movement in the anti backfire device. seems there was some wear in the bush in the inner cover allowing the anti device to move inwards towards the inner cover and the gears on the device were contacting the stainless steel plate that supports the hydraulic chain tensioner. I placed a couple of washers in the bush housing and this seems to have solved it.

The deep knocking noise is the 2 hydraulic chain tensioners bottoming out in their housings. When I blip the throttle you can see / hear them doing this. I have no idea why.

Questions.
1) Why have they decided to do this? I primed them with oil, which leaks out anyway thru the tiny holes. Will they self prime as time goes by? The other question is why do they not do this when the clutch plates are removed? something to do with load perhaps. New ones are $180AUD. would like to avoid the expense.

cheers Hiilbone

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I think you may have answered this in the previous thread but what kind of oil are you using?

Be sure the nylon spacers are in the right way with the springs, Chuck.

hillbone said:

The deep knocking noise is the 2 hydraulic chain tensioners bottoming out in their housings. When I blip the throttle you can see / hear them doing this. I have no idea why.

Questions.
1) Why have they decided to do this? I primed them with oil, which leaks out anyway thru the tiny holes. Will they self prime as time goes by?

Click to expand...

The MkIII automatic chain tensioner does take time to prime itself after the engine has been started.

If the oil in the tensioner reservoir has had time to drain through the tensioner mechanism, then the pistons will be slapped against the tensioner body by the action of the primary chain, because the lack of oil means they are working in an undamped condition as there must be a sufficient amount of oil within the tensioner cavity to cause a hydraulic lock to occur between the two pistons. The action of one piston then results in a reaction of the other = when one piston is forced inwards by the action of the primary chain, then the other piston is forced outwards against the opposite run of chain and thus primary chain tension is maintained. So the knocking noise is quite normal-and nothing to worry about provided the knocking stops after the engine has been running for a minute or so.

The thinner and hotter the oil is, then the faster it will drain from the tensioner, leaving it unprimed. ATF for instance, will completely drain from the tensioner in only a few minutes, and is one of the reasons why I wouldn't recommend it for a MkIII chain case.

[Edit] There is a small one-way ball valve where the tensioner reservoir feeds to the internal cavity, this valve of course must be working properly to stop oil being forced back to the reservoir by the action of the pistons.

At risk of hijacking the thread (therefore hijacking in progress) I have tried this afternoon to take out the fitting that retains the ball valve in my primary chain tensioner unit, but have found that it just spins around when turning the flats :!: Does this suggest stripped threads or is it a press fit :?: Does anybody know?

In anticipation.

If I remember correctly, I couldn't remove the valve from my own MkIII's tensioner either, so it probably is a press fit, and to the best of my knowledge the valve isn't available separately.

Thank you for the reply Les. I was beginning to wonder if I'd damaged my ball valve assembly. I was only trying to dismantle it to check it had no debris behind the ball.

Incidently I note that you always get better results using 20/50 in the primary case,, I have been running my primary with ATF (I managed to knacker the belt..... a long story) with good results regarding the auto tensioner. Just thought this might be of (some) interset.

Reggie said:

Incidently I note that you always get better results using 20/50 in the primary case,, I have been running my primary with ATF (I managed to knacker the belt..... a long story) with good results regarding the auto tensioner. Just thought this might be of (some) interset.

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I expect many MkIII owners will be content to use ATF in their chaincases, so I will at least give my reasons for preferring 20w/50 engine oil.

When I bought my MkIII, it had ATF in the chaincase, and I continued to use it, as that's what the majority of people were now using in their chaincases (even though it was never recommended by any British bike manufacturer for their chaincases, as far as I know?). However I heard from a reliable source on another forum that ATF possibly wasn't ideal for use in a MkIII chaincase, because it is too thin to adequately damp the tensioner mechanism.

Acting on that advice, I tried some 10w/40 engine oil, and I immediately noticed there was less low speed transmission snatch, presumably because the tensioner was doing a better job of controlling primary chain tension? I also thought the primary drive sounded quieter too, but that could have been my imagination? I also noticed the (bronze plate) clutch felt less grabby than it did with ATF. Subsequently, I tried the recommended 20w/50 oil, and the clutch action felt even better.


I also found that with engine oil, the tensioner primed itself more quickly, and there appeared to be less black gunge which tends to build up on the bronze plates and, as a result needs cleaning off every so often.

LAB wrote;

Acting on that advice, I tried some 10w/40 engine oil, and I immediately noticed there was less low speed transmission snatch, presumably because the tensioner was doing a better job of controlling primary chain tension? I also thought the primary drive sounded quieter too, but that could have been my imagination? I also noticed the (bronze plate) clutch felt less grabby than it did with ATF. Subsequently, I tried the recommended 20w/50 oil, and the clutch action felt even better.

Click to expand...

I might try some 20/50 and see if I notice a difference. I'm using Surflex plates in my clutch at the moment, and my main reluctance for putting in thicker oil was that I perceive a potential higher risk of clutch slip with the thicker oil, which I haven't had on my mK3 yet, but on my previous Norton was always an annoying problem :evil: that I could only solve for short periods with clutch plate cleaning...............but then I didn't have a Dave Conneau clutch pushrod oil seal fitted at that time, and I think that this is what probably makes most of the improvement (no more clutch slip).

How come i can't see this one way ball valve?. Where do I find it? Cheers hillbone

hillbone said:

How come i can't see this one way ball valve?. Where do I find it? Cheers hillbone

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Look at the tensioner body in the link:

The valve is the part that looks like a slotted head screw next to the stud [item 33]
If you look closely at yours, you should see it has a hole in it, and behind that hole should be a small ball bearing?

You will of course have to remove the plate [29] from the tensioner first.

Just like to add Thanks! Bought a Mk III last year and have a little work to do, it was gone over by an "Expert". Bought it with shift problems, ratchet spring needed to be adjusted. When I buy a bike the least I do is change all oil. I like heavier weight oils in my primaries. Then I read an article/post that heavy was not good and to use light/ATF. So I drained it out and put HD primary oil in. Seemed ok last ride. I have some time waiting on parts for another project, so I thought I'd put the stock air box on the bike, it came with the deal. So it's been a while since it was started. To my surprise it had a primary noise. Sounded like a nut had came off and was being picked up on occasion by the chain, scared the hell out of me! I think they used Yamaha Bond to attach outer primary! Nothing was inside the case everything looked ok and it has a new chain. But the tensioner was easy to collapse. Going to take tensioner apart and wash out check ball, found some gasket material inside cover. NO More thin oil for me. Will reassemble with at least 20-50. Riding season will be here sooner then we think.

mean gene said:

Just like to add Thanks! Bought a Mk III last year and have a little work to do, it was gone over by an "Expert". Bought it with shift problems, ratchet spring needed to be adjusted. When I buy a bike the least I do is change all oil. I like heavier weight oils in my primaries. Then I read an article/post that heavy was not good and to use light/ATF. So I drained it out and put HD primary oil in. Seemed ok last ride. I have some time waiting on parts for another project, so I thought I'd put the stock air box on the bike, it came with the deal. So it's been a while since it was started. To my surprise it had a primary noise. Sounded like a nut had came off and was being picked up on occasion by the chain, scared the hell out of me! I think they used Yamaha Bond to attach outer primary! Nothing was inside the case everything looked ok and it has a new chain. But the tensioner was easy to collapse. Going to take tensioner apart and wash out check ball, found some gasket material inside cover. NO More thin oil for me. Will reassemble with at least 20-50. Riding season will be here sooner then we think.

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Well I hope you notice that the parts manual has omitted the thin gasket that goes behind the hydraulic 2 plungers aluminum casting. You need it. It helps gather and distribute the 20W-50 oil. Pre 75 owners talk of the wonders of ATF , but MK 111 owners should stick to recommended by the manual primary fluids only.

Remind me again 'Why do we do this?" Of course there was no gasket under the plate and the last person tried to remove the plate without removing the alternator or starter safety. Bent out of shape no way was it retaining any oil! Also plastic buffers were in upside down if the parts pic is correct. Shank end goes into cylinder spring sits on hat and spring goes into housing

mean gene said:

Remind me again 'Why do we do this?" Of course there was no gasket under the plate and the last person tried to remove the plate without removing the alternator or starter safety. Bent out of shape no way was it retaining any oil! Also plastic buffers were in upside down if the parts pic is correct. Shank end goes into cylinder spring sits on hat and spring goes into housing

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My top hat spacers were also in upside down and the top one was a metal Allen bolt. In my view, having the spacers the wrong way round is what initially causes the plunger to stick, as it goes much deeper into the cylinder. My top one was also seized. I carefully dressed the plunger with oiled wet n dry, to get it moving smoothly. I got it working properly that way, with the hydraulic pressure still there. The torque specs for the 3 bolts are in the manual. I think over tightening causes the plate to warp.

Just as a warning: My bottom hydraulic plunger was fully extended and caused the chain to grind a path in the inner chain case. I think the alloy and oil sludge became grinding paste for my sprag clutch, which failed. I also replaced my clutch hub, possibly the wear (notching) might have been sped up by the sludge. But, the evidence was obvious on the chaincase and in the primary oil! You would have spotted it if you had the same problem. So, whoever saved a few pennies using the Allen bolt, cost me a few hundred pounds in replacement parts. Learnt how that side of the bike works though .

Mart UK said:

In my view, having the spacers the wrong way round is what initially causes the plunger to stick, as it goes much deeper into the cylinder.

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The plungers should slide freely all the way into the housing regardless and before the springs become coil-bound...





...Although AN apparently did supply some plungers that were bored too short internally causing the springs to become coil-bound.

Thanks LAB this pic is exactly what I needed I love this forum!!!!!

Back together after parts arrived from Andover Norton. Assembled and primed chain tensioner with gasket. Filled with 20-50 oil. Started and ran quiet. Went for a little ride shifted correctly. All is good in the world.

Torontonian said:

Well I hope you notice that the parts manual has omitted the thin gasket that goes behind the hydraulic 2 plungers aluminum casting. You need it. It helps gather and distribute the 20W-50 oil.

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The tensioner gasket 06.6570 goes between the tensioner body and the 06.6001 plate so seals the joint (the shape and the fact that the gasket has three stud holes identify where it belongs).
It would serve no purpose if fitted "behind" the tensioner casting.

I don't have a MKIII, but from following this thread and the others linked, it struck me what a clever little device the hydraulic chain tensioner is. If I understand it correctly oil drops from the primary and collects in the funnel shaped casting. On the outwards stroke of the plungers oil is sucked in through the ball valve, then as one plunger is compressed the bearing valve stops the oil evacuating and the plunger on the other side is forced out of the body, so tensioning the chain on both sides of the run. Is that correct?