Slow Monster rebuild - Page 71

350TSS · 17-12-2019, 05:57 PM

I only had a couple of hours in the garage today as I was suffering with a cold just coming to fruition.

I managed to swap over the wrongly installed valve cap seals without puncturing them either taking them off or replacing them. Whilst doing it I re-checked all the clearances. I had a about a 20 minute hiatus when I could not get the camshaft to sit back in its proper position until I realised that the drive side end shim was not properly located and would let the camshaft seat on the drive side bearing. Taking it out and locating the shim with some thick grease solved the issue.

Next I tackled replacement of the gear-change mechanism springs, purely a precautionary measure, although the old ones looked perfect and were working fine when the bike came off the road. The thought occurred to me that I might have just replaced some perfectly good ones with ones that are from a bad batch, incorrectly tempered or whatever. The new ones had slightly less aggressive bends so maybe they modified the design to limit the possibility of breakage.

When I painted the engine I made up a blanking plate for the starter motor hole, this was bolted on with 3 x 6mm hex head bolts inserted from inside the alternator case done up finger tight. The paint, of course, covered the threads exposed on the outside where the starter motor lives. Two came out OK as I could get access to the bolt head inside the alternator case, the third is the bolt that can only be accessed by inserting an allen key through the hole in the starter idler gear, plenty of access for an allen key but none available for a 10mm socket. After about half an hour trying to wedge the bolt so I could get the nut past the paint I had to take the idler gear off which is what I should have done in the first place. Doh!!!

I ordered one of these to heat the crankcase mouth around the studs that are to be replaced, my normal blow lamp I fear will saturate the area and mean a repaint.

https://www.ebay.co.uk/itm/133138149423

Darkness · 17-12-2019, 06:46 PM

And so useful for finishing creme brulee or Italian meringues too!

350TSS · 22-12-2019, 04:20 AM

Well I spent about 3 hours yesterday trying to remove the studs from the crankcase.
Having whipped the vertical barrel off I tried my new stud remover tool
https://www.cromwell.co.uk/shop/hand.../p/KEN5826760K
despite being a meaty piece of equipment (580g) it is a flawed design and does not work very well.

The wheel that is supposed to grip the stud is gnurled at 90 degrees so only the very peak of the gnurl catches the stud and as soon as you tighten further it moves into a valley and loosens before it grips again. Also the back side of the hole through which the stud is located is smooth chrome and the stud rather than being gripped tends to move around.
First I heated the crankcase with the little blow lamp as much as I dare, boiling off the residual WD40 squirted down the stud holes in the barrel overnight, then I tried the tool which I eventually managed to get to 80nM (twice the head torque down figure) but the stud was not for coming out. The studs are wasted in the middle and that torque level is a breaking level torque for the reduced diameter.
Discretion here is the better part of valour here I think. The old studs are staying

350TSS · 22-12-2019, 04:55 AM

Having reltuctantly made that decision (I have spent best part of £130 to have 8 spare studs and a heavy ornament in my tool box) I can move on.

The good news is that there as no evidence of blowby on the vertical piston and no scoring on the skirt. I will take the horizontal barrel off to check that one as well.

Thereafter all work will now be final assembly, maybe another 10 hours on the engine, assembling the alternator case, changing the outer crank bearing and renewing the seals and reassembling the sprag clutch then on the other side replacing the pump and renewing the clutch hub rubbers, the big seal in the clutch cover.
Then the engine can go back in the frame.
I cannot say how many hours are left to do because my Excel spreadsheet is on my other computer which spectacularly went bang last week but I susspect now down to 130 hours

350TSS · 01-01-2020, 12:12 PM

First venture into the garage for nearly a fortnight yesterday, bad cold and visiting relatives, stopped play.
It was too cold to stop long so looking for a quick job.
I thought I would close up the two cylinder heads, clean the rocker gasket faces and the cam bearing faces and bolt same to the two heads.
As I was about to bolt the cam bearings back into place I noticed that the shim washers which fit over the end of the camshaft before you slide the cam bearing on were different thicknesses. Then I managed to mix them up and have no idea which one is for the vertical cylinder and which for the horizontal cyinder.
I puzzled for some time as to how to measure which should go where.
After a while I concluded that since the cam is pulled toward the drive side bearing when the pulley nut is done up and the drive side bearing is an interference fit in the head there cannot be any camshaft end float.
The LH side bearing and cap are a slide fit on the tub end of the camshaft so the shims on that side are redundant as the lateral position of the camshaft is determined by the positioning of the interference fit bearing in the head. The position of the LH bearing laterally on the shaft is determined by inner face on the cap and the thickness of the gasket between the head and the bearing cap.
Provided the camshaft turns freely with no binding when the bearing cap is put on and torqued up with no gasket then the shim is redundant.
I hope I have explained this correctly and I think my logic is correct.
Am I missing something?

manwithredbike · 01-01-2020, 05:10 PM

I also mixed the shaft end thrust washers up when doing some head work a few years ago and thought much the same. The exploded diagram in the link (assuming it's the same motor as yours) has one at 0.2mm and one 0.5mm but doesn't say which goes where.
Maybe something to do with expansion i.e. vertical cylinder expanding a bit more?
https://www.motosparepartner.com/en/...camshaft_37933

350TSS · 02-01-2020, 03:30 AM

Thanks for the diagram, there are 2 sets of shims, drive side (20 in the diagram) and stub end (22 in the diagram) and they are different diameters with the drive side being larger diameter. I have only mixed up the stub end ones., which are the ones that come in 2 sizes, 0.2 and 0.5mm thick.
I shall build them up with the stub end shims installed but without the cam bearing gasket in place and torque them down and see if there is any binding. If there is no inding I will install the gaskets and the job will be done. If there is binding I will have to swap them round to get the shims in the right /original place.
Either way it is not really a problem, I just found it interesting that Ducati should design in superfluous components.

350TSS · 06-01-2020, 01:40 PM

I had a frustrating 3 hours in the garage yesterday, the plan was to re-fit the vertical cylinder barrel and head and remove the horizontal one and clean/decoke piston.
First I inverted the vertical piston in a jar of acetone and then after about half an hours soaking cleaned out the ring grooves with a tooth brush. the rings stayed on the piston as I wanted to avoid the risk of breaking them getiing them off. It worked a treat and the rings are now completely free to move.
I bought new gudgeon pin circlips from Moto Rapido and after inserting the gudgeon pin tried to fit a replacement. The one I had removed pinged across the garage striking a few metallic objects ( so at least I know it is not in the bowels of the crankcase) on the way and will never be seen again. I had no intention of refitting the old circlip but I did not have a sample of the old one to compare with the new ones.
After a good hour of struggling and with the crankcase mouth stuffed full of paper towels I still had not manged to get the circlip to engage properly in its groove.
I find when something goes badly it is as well to walk away and do something else for a while then come back to it afresh.
So I moved onto removing the horizontal cylinder.
An hour and a half later the cylinder had risen about 6 mm from its face on the crankcase. Galvanic corrosion between the aluminium barrel and the cylinder head studs was the culprit.
After a lot of tuggung and jiggling and a block of wood and a hide mallet on the cylinder base it eventually came off.
To clean out the stud holes I cut a slot in the end of a length of 8mm aluminium bar and put a strip of emery paper in the slot and reamed the corrosion out of the stud holes with the battery drill.
I then managed to remove one of the circlips from the horizontal piston without it disappearing into the nether regions of the garage.
The fitted circlips and the supplied circlips are not the same at all.
The fitted ones have a 90 degree bend at one end that will engage nicely with the machined indent in the piston adjacent to the circlip groove. The supplied ones have no such bend and are approximately 1mm bigger in diameter than the old one. I think I have the wrong ones.
So all three hours achieved was removal of the front cylinder barrel and a few paint chips on the outside of the starter motor where I resorted to a screwdriver as a lever to remove the barrel.

350TSS · 06-01-2020, 01:48 PM

Top tip:
Brake cleaner removes coppaslip grease from Christmas new jeans.
"don't go into the garage with your new jeans on"
"I'm not doing anything dirty I just want to measure something"
I manage to knock the coppaslip tin off the bench and the dirty rim runs down my leg on its way down
"Oh!! ****!!!"
It really does remove one of the most stubborn stains known to man.

Ron1000 · 06-01-2020, 04:10 PM

Been there. Coppaslip engrained into my fancy jeans, my wife says even my nice clothes are slowly getting grubby.

As for brake cleaner. I used rock oil stuff this winter. Says it’s safe on everything and can be used a general degreaser too. Happy days.

350TSS · 06-01-2020, 11:31 PM

Craig at Moto Rapido says "very early Monsters had the ears on the gudgeon pin circlips, these were superceded with the circlips without the ears"
Anyne have tiips about how to install the later "uneared" circlips? because I am really struggling to get them to engage in the circlip groove.
If none are forthcoming I think I shall grind about 2 to 3mm fron each end and see if that alleviates installation.

Luddite · 07-01-2020, 12:00 AM

Have a look at this Mahle video, particularly the home-made installation tool at 4:40, which I'm sure you could knock up on your lathe in no time...

https://youtu.be/3kdhGBCpuxM

350TSS · 09-01-2020, 01:19 AM

Thanks Luddite, I think I will give that a go. I love stuff like that.
The problem really I think is very restricted access, even with the piston at TDC the centre of the gudgeon pin is only 40 to 50mm above the mouth of the crankcase. I need snipe nose pliers to get one end of the circlip to engage in the nib in the piston and to hold it there, then you need another tool to chase the remainder of the circlip around its circumference, all the while trying to stop the rings bashing against the studs.

350TSS · 09-01-2020, 02:19 AM

As I am waiting for various parts (particularly the green seals that fit on the crankcase beneath the barrels), I thought I would try to make progress by fitting the 4 x valve covers and the 2 x cam bearing caps to the cylinder heads.

From new, the valve covers were fitted using some grey silicone material and it is an absolute bugger to get off. It seems to be too elastic to scrape off and the only chemical that had any effect was acetone which also affects the powder coating that I am trying to preserve on the outer surface of the valve caps. Eventually, I got 8 nice clean mating surfaces.

The valve cover gaskets that came in the top end set are thin aluminium, coated with a dark grey rubbery material, and perhaps foolishly, I decided to fit them without gasket cement.

I was just about to fit the cam bearing caps when I discovered one of the cam bearings had managed to get some corrosion in it. They had been stored, carefully wrapped in bubble wrap, inside a sealed plastic box. Bugger!!!! Lesson, thorougly lube bearings before you store them.

I will need a blind bearing puller to get the offending bearing out. Looking on fleabay all the reasonably priced (read cheap c £30) ones work on the principle of a slide hammer which, if I am to preserve the powder coaring on the outer surface, will not work for me. I will need a bridge type puller so that the outer surface is not subjected to the vice and shock loadings.

Some of the reasonably priced puller sets (c£80) include a bridge type puller but they all have a fixed span for the bridge and rely on the legs pivoting at the ends of the bridge. I am sceptical that these will work as any misalignment will cause the bridge to collapse when any pressure is exerted.

To cut a long story short, I will very shortly be the proud owner of (for me) an expensive blind bearing puller set (all for the sake of a few squirts of oil before storing the cam bearing caps).

utopia · 09-01-2020, 01:34 PM

A minor point but I have always fitted those rubber coated valve cover gaskets dry and have never had a problem.
I believe mine are the original gaskets, they never had any sealant on them from new as far as I know and the bike has done nearly 30k miles on them.
I've probably had them off half a dozen times or so and although I bought a new set when I first got the bike, they remain unused in their packets cos the old ones have been fine.

I did have a ponder on your camshaft shim issue and although like you I couldn't see the need for them, I would be very sceptical that Ducati have fitted unnecessary parts and would advise treading very carefully there .. particularly since they supply the shims in two different thicknesses.
The only explanation that makes any sense to me (but still not much) is that it could be a hang-over from the original bevel drive cam arrangement.
But anyway, your plan to determine which went where seems reasonably sound.

17-12-2019, 06:46 PM	#2
Darkness . Join Date: May 2007 Location: Stockbridge Bike: M900 Posts: 1,984	And so useful for finishing creme brulee or Italian meringues too! __________________ Original and Best since 1993

01-01-2020, 05:10 PM	#6
manwithredbike aka Phil Join Date: Nov 2005 Location: derry Bike: M900 Posts: 376	I also mixed the shaft end thrust washers up when doing some head work a few years ago and thought much the same. The exploded diagram in the link (assuming it's the same motor as yours) has one at 0.2mm and one 0.5mm but doesn't say which goes where. Maybe something to do with expansion i.e. vertical cylinder expanding a bit more? https://www.motosparepartner.com/en/...camshaft_37933 __________________ .. ~

17-12-2019, 05:57 PM	#1
350TSS Too much time on my hands member Join Date: Jan 2013 Location: Shipbourne Bike: M900 Posts: 1,421	I only had a couple of hours in the garage today as I was suffering with a cold just coming to fruition. I managed to swap over the wrongly installed valve cap seals without puncturing them either taking them off or replacing them. Whilst doing it I re-checked all the clearances. I had a about a 20 minute hiatus when I could not get the camshaft to sit back in its proper position until I realised that the drive side end shim was not properly located and would let the camshaft seat on the drive side bearing. Taking it out and locating the shim with some thick grease solved the issue. Next I tackled replacement of the gear-change mechanism springs, purely a precautionary measure, although the old ones looked perfect and were working fine when the bike came off the road. The thought occurred to me that I might have just replaced some perfectly good ones with ones that are from a bad batch, incorrectly tempered or whatever. The new ones had slightly less aggressive bends so maybe they modified the design to limit the possibility of breakage. When I painted the engine I made up a blanking plate for the starter motor hole, this was bolted on with 3 x 6mm hex head bolts inserted from inside the alternator case done up finger tight. The paint, of course, covered the threads exposed on the outside where the starter motor lives. Two came out OK as I could get access to the bolt head inside the alternator case, the third is the bolt that can only be accessed by inserting an allen key through the hole in the starter idler gear, plenty of access for an allen key but none available for a 10mm socket. After about half an hour trying to wedge the bolt so I could get the nut past the paint I had to take the idler gear off which is what I should have done in the first place. Doh!!! I ordered one of these to heat the crankcase mouth around the studs that are to be replaced, my normal blow lamp I fear will saturate the area and mean a repaint. https://www.ebay.co.uk/itm/133138149423

22-12-2019, 04:20 AM	#3
350TSS Too much time on my hands member Join Date: Jan 2013 Location: Shipbourne Bike: M900 Posts: 1,421	Well I spent about 3 hours yesterday trying to remove the studs from the crankcase. Having whipped the vertical barrel off I tried my new stud remover tool https://www.cromwell.co.uk/shop/hand.../p/KEN5826760K despite being a meaty piece of equipment (580g) it is a flawed design and does not work very well. The wheel that is supposed to grip the stud is gnurled at 90 degrees so only the very peak of the gnurl catches the stud and as soon as you tighten further it moves into a valley and loosens before it grips again. Also the back side of the hole through which the stud is located is smooth chrome and the stud rather than being gripped tends to move around. First I heated the crankcase with the little blow lamp as much as I dare, boiling off the residual WD40 squirted down the stud holes in the barrel overnight, then I tried the tool which I eventually managed to get to 80nM (twice the head torque down figure) but the stud was not for coming out. The studs are wasted in the middle and that torque level is a breaking level torque for the reduced diameter. Discretion here is the better part of valour here I think. The old studs are staying

22-12-2019, 04:55 AM	#4
350TSS Too much time on my hands member Join Date: Jan 2013 Location: Shipbourne Bike: M900 Posts: 1,421	Having reltuctantly made that decision (I have spent best part of £130 to have 8 spare studs and a heavy ornament in my tool box) I can move on. The good news is that there as no evidence of blowby on the vertical piston and no scoring on the skirt. I will take the horizontal barrel off to check that one as well. Thereafter all work will now be final assembly, maybe another 10 hours on the engine, assembling the alternator case, changing the outer crank bearing and renewing the seals and reassembling the sprag clutch then on the other side replacing the pump and renewing the clutch hub rubbers, the big seal in the clutch cover. Then the engine can go back in the frame. I cannot say how many hours are left to do because my Excel spreadsheet is on my other computer which spectacularly went bang last week but I susspect now down to 130 hours

01-01-2020, 12:12 PM	#5
350TSS Too much time on my hands member Join Date: Jan 2013 Location: Shipbourne Bike: M900 Posts: 1,421	First venture into the garage for nearly a fortnight yesterday, bad cold and visiting relatives, stopped play. It was too cold to stop long so looking for a quick job. I thought I would close up the two cylinder heads, clean the rocker gasket faces and the cam bearing faces and bolt same to the two heads. As I was about to bolt the cam bearings back into place I noticed that the shim washers which fit over the end of the camshaft before you slide the cam bearing on were different thicknesses. Then I managed to mix them up and have no idea which one is for the vertical cylinder and which for the horizontal cyinder. I puzzled for some time as to how to measure which should go where. After a while I concluded that since the cam is pulled toward the drive side bearing when the pulley nut is done up and the drive side bearing is an interference fit in the head there cannot be any camshaft end float. The LH side bearing and cap are a slide fit on the tub end of the camshaft so the shims on that side are redundant as the lateral position of the camshaft is determined by the positioning of the interference fit bearing in the head. The position of the LH bearing laterally on the shaft is determined by inner face on the cap and the thickness of the gasket between the head and the bearing cap. Provided the camshaft turns freely with no binding when the bearing cap is put on and torqued up with no gasket then the shim is redundant. I hope I have explained this correctly and I think my logic is correct. Am I missing something?

02-01-2020, 03:30 AM	#7
350TSS Too much time on my hands member Join Date: Jan 2013 Location: Shipbourne Bike: M900 Posts: 1,421	Thanks for the diagram, there are 2 sets of shims, drive side (20 in the diagram) and stub end (22 in the diagram) and they are different diameters with the drive side being larger diameter. I have only mixed up the stub end ones., which are the ones that come in 2 sizes, 0.2 and 0.5mm thick. I shall build them up with the stub end shims installed but without the cam bearing gasket in place and torque them down and see if there is any binding. If there is no inding I will install the gaskets and the job will be done. If there is binding I will have to swap them round to get the shims in the right /original place. Either way it is not really a problem, I just found it interesting that Ducati should design in superfluous components.

06-01-2020, 01:40 PM	#8
350TSS Too much time on my hands member Join Date: Jan 2013 Location: Shipbourne Bike: M900 Posts: 1,421	I had a frustrating 3 hours in the garage yesterday, the plan was to re-fit the vertical cylinder barrel and head and remove the horizontal one and clean/decoke piston. First I inverted the vertical piston in a jar of acetone and then after about half an hours soaking cleaned out the ring grooves with a tooth brush. the rings stayed on the piston as I wanted to avoid the risk of breaking them getiing them off. It worked a treat and the rings are now completely free to move. I bought new gudgeon pin circlips from Moto Rapido and after inserting the gudgeon pin tried to fit a replacement. The one I had removed pinged across the garage striking a few metallic objects ( so at least I know it is not in the bowels of the crankcase) on the way and will never be seen again. I had no intention of refitting the old circlip but I did not have a sample of the old one to compare with the new ones. After a good hour of struggling and with the crankcase mouth stuffed full of paper towels I still had not manged to get the circlip to engage properly in its groove. I find when something goes badly it is as well to walk away and do something else for a while then come back to it afresh. So I moved onto removing the horizontal cylinder. An hour and a half later the cylinder had risen about 6 mm from its face on the crankcase. Galvanic corrosion between the aluminium barrel and the cylinder head studs was the culprit. After a lot of tuggung and jiggling and a block of wood and a hide mallet on the cylinder base it eventually came off. To clean out the stud holes I cut a slot in the end of a length of 8mm aluminium bar and put a strip of emery paper in the slot and reamed the corrosion out of the stud holes with the battery drill. I then managed to remove one of the circlips from the horizontal piston without it disappearing into the nether regions of the garage. The fitted circlips and the supplied circlips are not the same at all. The fitted ones have a 90 degree bend at one end that will engage nicely with the machined indent in the piston adjacent to the circlip groove. The supplied ones have no such bend and are approximately 1mm bigger in diameter than the old one. I think I have the wrong ones. So all three hours achieved was removal of the front cylinder barrel and a few paint chips on the outside of the starter motor where I resorted to a screwdriver as a lever to remove the barrel.

06-01-2020, 01:48 PM	#9
350TSS Too much time on my hands member Join Date: Jan 2013 Location: Shipbourne Bike: M900 Posts: 1,421	Top tip: Brake cleaner removes coppaslip grease from Christmas new jeans. "don't go into the garage with your new jeans on" "I'm not doing anything dirty I just want to measure something" I manage to knock the coppaslip tin off the bench and the dirty rim runs down my leg on its way down "Oh!! ****!!!" It really does remove one of the most stubborn stains known to man.

06-01-2020, 04:10 PM	#10
Ron1000 Registered User Join Date: Jun 2015 Location: Livingston Bike: M1100evo Posts: 863	Been there. Coppaslip engrained into my fancy jeans, my wife says even my nice clothes are slowly getting grubby. As for brake cleaner. I used rock oil stuff this winter. Says it’s safe on everything and can be used a general degreaser too. Happy days.

06-01-2020, 11:31 PM	#11
350TSS Too much time on my hands member Join Date: Jan 2013 Location: Shipbourne Bike: M900 Posts: 1,421	Craig at Moto Rapido says "very early Monsters had the ears on the gudgeon pin circlips, these were superceded with the circlips without the ears" Anyne have tiips about how to install the later "uneared" circlips? because I am really struggling to get them to engage in the circlip groove. If none are forthcoming I think I shall grind about 2 to 3mm fron each end and see if that alleviates installation.

07-01-2020, 12:00 AM	#12
Luddite Registered User Join Date: Aug 2011 Location: Southampton Bike: M1100evo Posts: 2,465	Have a look at this Mahle video, particularly the home-made installation tool at 4:40, which I'm sure you could knock up on your lathe in no time... https://youtu.be/3kdhGBCpuxM

09-01-2020, 01:19 AM	#13
350TSS Too much time on my hands member Join Date: Jan 2013 Location: Shipbourne Bike: M900 Posts: 1,421	Thanks Luddite, I think I will give that a go. I love stuff like that. The problem really I think is very restricted access, even with the piston at TDC the centre of the gudgeon pin is only 40 to 50mm above the mouth of the crankcase. I need snipe nose pliers to get one end of the circlip to engage in the nib in the piston and to hold it there, then you need another tool to chase the remainder of the circlip around its circumference, all the while trying to stop the rings bashing against the studs.

09-01-2020, 02:19 AM	#14
350TSS Too much time on my hands member Join Date: Jan 2013 Location: Shipbourne Bike: M900 Posts: 1,421	As I am waiting for various parts (particularly the green seals that fit on the crankcase beneath the barrels), I thought I would try to make progress by fitting the 4 x valve covers and the 2 x cam bearing caps to the cylinder heads. From new, the valve covers were fitted using some grey silicone material and it is an absolute bugger to get off. It seems to be too elastic to scrape off and the only chemical that had any effect was acetone which also affects the powder coating that I am trying to preserve on the outer surface of the valve caps. Eventually, I got 8 nice clean mating surfaces. The valve cover gaskets that came in the top end set are thin aluminium, coated with a dark grey rubbery material, and perhaps foolishly, I decided to fit them without gasket cement. I was just about to fit the cam bearing caps when I discovered one of the cam bearings had managed to get some corrosion in it. They had been stored, carefully wrapped in bubble wrap, inside a sealed plastic box. Bugger!!!! Lesson, thorougly lube bearings before you store them. I will need a blind bearing puller to get the offending bearing out. Looking on fleabay all the reasonably priced (read cheap c £30) ones work on the principle of a slide hammer which, if I am to preserve the powder coaring on the outer surface, will not work for me. I will need a bridge type puller so that the outer surface is not subjected to the vice and shock loadings. Some of the reasonably priced puller sets (c£80) include a bridge type puller but they all have a fixed span for the bridge and rely on the legs pivoting at the ends of the bridge. I am sceptical that these will work as any misalignment will cause the bridge to collapse when any pressure is exerted. To cut a long story short, I will very shortly be the proud owner of (for me) an expensive blind bearing puller set (all for the sake of a few squirts of oil before storing the cam bearing caps).

09-01-2020, 01:34 PM	#15
utopia No turn left unstoned Join Date: Jun 2010 Location: leicester Bike: M750 Posts: 4,546	A minor point but I have always fitted those rubber coated valve cover gaskets dry and have never had a problem. I believe mine are the original gaskets, they never had any sealant on them from new as far as I know and the bike has done nearly 30k miles on them. I've probably had them off half a dozen times or so and although I bought a new set when I first got the bike, they remain unused in their packets cos the old ones have been fine. I did have a ponder on your camshaft shim issue and although like you I couldn't see the need for them, I would be very sceptical that Ducati have fitted unnecessary parts and would advise treading very carefully there .. particularly since they supply the shims in two different thicknesses. The only explanation that makes any sense to me (but still not much) is that it could be a hang-over from the original bevel drive cam arrangement. But anyway, your plan to determine which went where seems reasonably sound.