primary chain hydraulic tensioner assembly doesnt make sense

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Great, the same as the the one I just removed from the sample bike, and the purchasing records going back to when Renolds could no longer supply the kits.
 

guest76

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@Madnorton - Ashley, could you pull a couple from stock and see if the dimensions of the components are as far removed from the originals as reported?

It would be interesting to find out of the reported incident is a one off.

Thanks!
 
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They sure are, 3.2'' I also have a tensioner kicking around at home from the project bike, will climb into the loft and check it tonight. Being a MK3 owner myself I have an interest in this one.
 

p400

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i dont see the starting spring length as the issue here, but the coil count is important. 26 vs 29

The part creating the issue is the new replacement plunger with a "shortened" bore depth.....unable to accommodate the white plastic piston at the correct depth and unable to accept the 29 coil count spring.

This shortened bore depth places the white plastic piston at the wrong relationship to the small hole in the plunger tube.
 

guest76

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@p400 your white plastic piece and spring both look different to the ones in the Andover kit 06.5341 https://andover-norton.co.uk/en/shop-details/16496/p-chain-tensioner-plunger-69-0622-2-per-bike-

7CDF1221-1D4D-4488-8345-879BA0FC6B52.jpeg

The coil count on the Andover spring is indeed 29, but the coils look closer together than on your spring.

The thick ‘head’ part of the white plastic piece also looks thicker on the Andover picture compared to yours.
 

jimbo

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FYI,installed the original plastic pieces with their heads toward the springs as determined to be correct. When riding the bike I cannot feel or notice any difference compared to when I had the plastic piece the wrong way. It might take a while for the plungers to pump up, but there is still some slap at certain times .
 

p400

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Just received two new tensioner kits 06.5341

It is supplied with a white plastic pistons as shown (not as pictured on web site)
29 coil spring , length 3.2"

The problem is still the bore length in the new plunger at 1.745"
instead of the required 1.895" to match original configuration.

I am also not seeing any discussion , on this forum/thread, around the ball check in the alloy body.

20190528_NewAndoverMk3Tensioners1.jpg
 

p400

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What are the service implications of this Primary chain tensioner ball check?

Needs no service ever?

The ball check shown below is free to roll about. Should it be spring loaded?


20190528_BallCheckTensioner2.jpg
 

p400

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My issue is the ability to install the new Andover pieces and have a functioning primary chain tensioner.

The Andover supplied plunger is too short internally and this creates two problems
1. the white plastic piston does not relate to the plunger bleed hole as OEM.
2. when Andover white plastic piston and 29 coil count spring installed as the blueprint shows, the tensioner cannot fully retract on either end as OEM.
3. This inability for the plunger to retract, at least on the top run of primary chain, forces the top run of chain upward.....and this means the plunger foot is going to be "chainsawed" into rubber bit failure.

This issue does not occur with OEM pieces/dimensions.

What are Norton Mk3 owners doing?

20190528_PrimaryChainTopRun1.jpg
 

MichaelB

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With the longer spring and shorter depth, will it work with the white piece reversed?
If not, A/N has a real pile here.
 

p400

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I am not worried about my Mk3, but this maintenance is not my Mk3.
This particular Mk3 had the white plastic piston installed backwards which allowed the plungers to retract.

I was hoping some owner/engineer had resolved how to make this Mk3 tensioner work with whatever new parts were offered.
Maybe cut off the white plastic piston, small end, until it matched the OEM relationship with the bleed hole.
1.895 - 1.745 = 0.150"
Then cut off 3 coils off a 29 coil spring to match coil bound length of OEM.

Or does someone supply correct pieces?

And what about the ball check?

Maybe when all the new Andover pieces are put together it all works (retracts)?
(This would mean the white plastic piston position and tiny bleed hole were not important?)
 
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jimbo

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If the patent has listed names( you can look it up), try to contact those persons. I did that with John Favill the co-inventor of the "Bean Can" mufflers and had a very nice correspondence with him. Other wise you will need to reverse engineer the assembly.

DSC09696.jpg
 
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Precisely, so you've replaced incorrectly dimensioned parts with more of the same, but you bought an original plunger kit so why not use it on the top run?



This particular Mk3 owner is still happily using original parts.

This Original MKIII owner is still running OEM parts @ 74k miles.
Ride On
Dave
 
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I found one set of my tensioner components. lengths, wire size and 26 coils all same as LAB.
Any reason not to shorten the nylon spacers by the .150 difference in depth of the short bore?
Air purge and bore oiler bleed hole will then align roughly to the top of the nylon spacer.
Then shorten the nylon piston another .116" so the 29 coil long spring will not get coil bound.
All in all, mainly a slightly stiffer pair of springs against the pistons/chain.
Top tensioner is the quick reacting piston and the bottom one get slowly filled from the top tensioner and is only slowly allowed to bleed off through the air/oiler holes. Hope the tiny fill hole never gets a bit of grit or black sludge/residue from a fiber friction plate.
Started to formulate a theory on the detrimental effect of the black sludge on the sprag performance.
 

jimbo

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Other wise you will need to reverse engineer the assembly.
I found one set of my tensioner components. lengths, wire size and 26 coils all same as LAB.
Any reason not to shorten the nylon spacers by the .150 difference in depth of the short bore?
Air purge and bore oiler bleed hole will then align roughly to the top of the nylon spacer.
Then shorten the nylon piston another .116" so the 29 coil long spring will not get coil bound.
All in all, mainly a slightly stiffer pair of springs against the pistons/chain.
Top tensioner is the quick reacting piston and the bottom one get slowly filled from the top tensioner and is only slowly allowed to bleed off through the air/oiler holes. Hope the tiny fill hole never gets a bit of grit or black sludge/residue from a fiber friction plate.
Started to formulate a theory on the detrimental effect of the black sludge on the sprag performance.
 
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Frankly, at least 50% of the replacement parts I have purchased need some sort of fettling to fit - this has even included such mundane items as fasteners whereas all original parts, whether NOS or used, interchange with no issue at all. ;)

One example - I received a new air filter back plate for my '73 Commando with the tabs for the bolts in the wrong location. They would not align with the filter/front plate in position.I had to cut the tabs off and tack weld them in the correct location.
 
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p400

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It is becoming obvious when disassembling other Mk3 primary chain tensioners............and finding the plastic piece the wrong way and the spring stretched out to a new, longer free length...........and finding that this "wrong" orientation has worked seemingly okay for thousands of miles.....that the "wrong" way works reasonably well.

Why does the Andover included drawing show a configuration that does not work in practice?
 

L.A.B.

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Why does the Andover included drawing show a configuration that does not work in practice?

You'd really have to ask Andover Norton as they are (or at least were) unaware their tensioner parts aren't made to the original dimensions.
 
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