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Minisport Duplex Vernier Kit


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#1 govig

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Posted 23 March 2019 - 08:50 PM

I have been trying to fit this duplex vernier timing chain kit from MiniSport part # C-AJJ3327.

 

The problem is the sprockets won't line up and with all the crankshaft shims behind the bottom sprocket taken out, the cam sprocket is still about 20 thou too far back (or the crank sprocket too far forward) .

 

Another way of describing the problem is that to line the sprockets up, it could do with some shims behind the cam sprocket (yes I know that's not possible).

 

Has anyone else had this problem with this expensive kit?

 

The motor is a 1275 A+ from a Spi.

 

 



#2 nicklouse

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Posted 23 March 2019 - 09:09 PM

what front plate are you using?

and the cam retaining plate is it new?

and you have used the correct thickness of gasket between the block and front plate?



#3 InnoCooperExport

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Posted 23 March 2019 - 10:05 PM

Have you replaced the bolts in the engine plate behind the crank sprocket with countersunk screws? Otherwise the crank sprocket can't go far enough back and will fowl on those bolts.

#4 govig

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Posted 23 March 2019 - 10:46 PM

Thanks fore the ideas but

 

what front plate are you using?

and the cam retaining plate is it new?

and you have used the correct thickness of gasket between the block and front plate?

 

Standard

 

No but the motor has only done 8,000 miles and the cam endfloat is normal.

 

Yes, there is only A+ and A gaskets aren't there?

 

 

I am suspecting the kit at this stage because if the old simplex sprockets and chain are put back, shims are required behind the crank sprocket as expected. The gasket, front plate and cam retaining plate remain the same.



#5 govig

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Posted 23 March 2019 - 10:48 PM

 

Have you replaced the bolts in the engine plate behind the crank sprocket with countersunk screws? Otherwise the crank sprocket can't go far enough back and will fowl on those bolts. 

 

No the standard bolts have been put back and are not fouling the crank sprocket. The back of the sprocket meets the crank shoulder without going anywhere near the heads of the two bolts.



#6 cal844

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Posted 23 March 2019 - 11:14 PM

Could the op perhaps post some images of the issue, to make it clearer for us all?

I know there Will be a few ways to fix this

#7 Moke Spider

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Posted 24 March 2019 - 05:52 AM

The lobes on the Cam are (or should be !!!) Tapered and all the same way. When the Cam rotates, it will naturally Thrust forward, in to the Cam Thrust Plate.

 

So, when checking for alignment of the Sprockets, ensure the Cam is thrusted in to the Thrust Plate (that's the Triangular Plate in front of the Cam and behind the Sprocket)

 

The other thing is have you got your Front Engine Plate Gasket fitted in there?



#8 govig

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Posted 24 March 2019 - 10:21 AM

Hmmm.... If all the cam endfloat is taken up by spragging the sprocket forward, the sprockets just about line up but without any shims behind the crank sprocket. 

 

As MS says the cam will run in this position when rotating and yes MS, I have got a front cover gasket : )

 

Without changing anything else, if I put the original simplex kit back on, I need shims. The only variable is therefore the sprockets and I think the duplex kit crank sprocket could do with 30 thou milling off the back of it so shims could be used as normal. Or use two front plate gaskets... Good old MiniSport  :unsure:

 

Only question now is to use the A+ chain tensioner or not....

 

PS MS this motor is going in a Moke.


Edited by govig, 24 March 2019 - 10:25 AM.


#9 imack

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Posted 24 March 2019 - 10:43 AM

No tensioner on duplex

#10 nicklouse

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Posted 24 March 2019 - 12:00 PM

The lobes on the Cam are (or should be !!!) Tapered and all the same way. When the Cam rotates, it will naturally Thrust forward, in to the Cam Thrust Plate.

 

So, when checking for alignment of the Sprockets, ensure the Cam is thrusted in to the Thrust Plate (that's the Triangular Plate in front of the Cam and behind the Sprocket)

 

The other thing is have you got your Front Engine Plate Gasket fitted in there?

Chris,

this interesting and is what i have always done. But it got me thinking how did i know this. so went to the manuals and there is nothing there at all, that i can see at the moment.  i can only think it was from my engine builder/machine shop.

 

If it is really lacking in the manuals we need a sticky covering it.



#11 nicklouse

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Posted 24 March 2019 - 12:01 PM

No tensioner on duplex

some engine builders would disagree on that.



#12 govig

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Posted 24 March 2019 - 01:41 PM

 

 

Have you replaced the bolts in the engine plate behind the crank sprocket with countersunk screws? Otherwise the crank sprocket can't go far enough back and will fowl on those bolts. 

 

No the standard bolts have been put back and are not fouling the crank sprocket. The back of the sprocket meets the crank shoulder without going anywhere near the heads of the two bolts.

 

:D See what you mean now I've put the chain on.....

 

I hadn't got as far as putting the sprockets and chain on together.

 

Yep the duplex chain fouls the bolt hex, I thought you meant the new duplex sprocket fouled them.

 

Anyway, all now sorted with two front plate gaskets. Thanks for your collective help.



#13 Moke Spider

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Posted 24 March 2019 - 06:54 PM

Only question now is to use the A+ chain tensioner or not....

 

PS MS this motor is going in a Moke.

 

While a tensioner isn't needed with a Duplex. I still fit one if the engine I'm assembling has the later (for us !) Engine Plate and Chain Cover.

 

If it's going in a Moke then best get it all perfect :D

 

 

 

The lobes on the Cam are (or should be !!!) Tapered and all the same way. When the Cam rotates, it will naturally Thrust forward, in to the Cam Thrust Plate.

 

So, when checking for alignment of the Sprockets, ensure the Cam is thrusted in to the Thrust Plate (that's the Triangular Plate in front of the Cam and behind the Sprocket)

 

The other thing is have you got your Front Engine Plate Gasket fitted in there?

Chris,

this interesting and is what i have always done. But it got me thinking how did i know this. so went to the manuals and there is nothing there at all, that i can see at the moment.  i can only think it was from my engine builder/machine shop.

 

If it is really lacking in the manuals we need a sticky covering it.

 

 

I have bought this up a few times in other threads, one has a diagram.

 

I know it's not covered in the Factory Manuals as they are written for the professional mechanic and so assume they already know this.



#14 Wiggy

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Posted 24 March 2019 - 09:44 PM

I've read a few times that you don't need a tensioner for a Duplex Chain, but why is that?

Just curious.

#15 Moke Spider

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Posted 24 March 2019 - 09:52 PM

I've read a few times that you don't need a tensioner for a Duplex Chain, but why is that?

Just curious.

 

The early 1275's from 1963 (though these were 1071 in that year) up to 1977-ish had a Duplex set up and no tensioner at all, after which they went to Simplex and with a Tensioner. I've run engines with a Duplex Chain for around 80 000 km while they did have slack, there was no rattle from them.

 

The 998 and other small bore engines also went to a different Tensioner in 1979. Prior to 79, while having a Simplex, they did have 'Tensioners' by way of 2 Rubber Rings in the Cam Sprocket.

 

I do prefer to fit a tensoner regardless of the set up as it's that little more 'refined' with less timing scatter at lower revs.






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