All, Putting above mentioned cam bearings and speedo drive worm gear back together. The gear goes between the inner (SKF 6004 C3) and outer (SKF 6003 C3) bearings (as you know). What's the trick to getting them pulled up together so the gear is driven, but not where the bearings are clamped too tight. Cheers Gaz
The gear is clamped between the 2 bearing inners so there is no axial load on the bearings. You tighten the cam pulley nut to the specified 70 Nm and that's all there is to it.
I thought it should be the tacho drive..............but if you want make sure the worm gear (which acts as a bearing spacer) doesn't slip, even though you may get the nut fully tightened, why not put a spot of Loctite bearing fit on the cam just where the drive slips on...... ......you have about 20 minutes to complete the assembly and tighten the nut.
Strangely enough it doesn't Pete, although at one time the camshafts had a slot milled for a Woodruffe key. This from the 907ie parts list.
Same as the 900SS camshaft.........most had the second woodruff key slot for the worm drive, but didn't actually use the woodruff key. The 750SS doesn't even have the slot (unless the very early ones do), and I suspect neither does the 600 or the 400. This is why the tacho drive can fail if and get chewed up, if the cam pulley silly nut doesn't get tightened properly.....the worm gets slack on the camshaft and can also move sideways slightly, which is enough for the pinion and the worm to start mis-meshing. Both items marked '13' in the diagram.
Sorry, I didn't realise that. My Pantah engines all have the Woodruff key, which is just fine (provided you remember it when removing a camshaft from a front head). So the factory must have dropped the keying at some point in the 1980s, presumably. Wonder why?
They had dropped them by the time the 750 Paso was introduced in 1985. Why? Bean counters I guess. Somebody must have decided it wasn't necessary. The cost of all those keys and machining the slot in the camshafts would add up to a fair bit over a year and Cagiva took over at a time when Ducati was on the brink of extinction.
Sorry your are correct AL - tacho drive. Ok the diagram is a 907ie, it shows the gear the wrong side of the outer bearing for the 900ss set up, obviously a different set up. I had not thought any further on than pressing the bearings in, but can now see the assembly is all locked up through the cam shaft / inner bearing "inner" / gear / outer bearing "inner" / spacer / large washer / pulley / nut. Sorry it's been a long time since I took it apart. But I still think you can axially load the bearings up if you press the outer bearing (pressed in using "outer") in too far. Or if you do not press it in far enough and then tighten the silly nut up the "inner" will load "outer" by trying to move it through the bearings. Is it a case of pressing the outer bearing in and keeping an eye on the axial movement of the gear. Press it in bit by bit and when you have a snug fit where the gear does not drop between the bearing "inners" - stop pressing. Then when the assembly is locked up with the nut there is minimal relative movement of "inner" & "outer" of the outer bearing. Or am I still not getting this. Cheers Gaz
That did cross my mind. Anyway what about this. I have been going down the path of pressing bearing in on "outer" as thats where it's located. Just looking at the bearing I am pretty sure "inner" & "outer" are same width and ground. If I press it in with something that was flat and supported both "inner" & "outer" in the same plane it would pinch the bearing and gear Assy up on the "inners" and locate the "outer" in the right position so not to move when the whole assy was locked up with the silly nut. Does that sound any better or am I still talking Bo!!ocks. Cheers Gaz.
See diagram for the 750 below.......should be the same as near as dammit for the 900. The middle bearing outer race should be hard against it's seat inside the head. The cam has a shoulder which sits right inside the middle bearing with a thrust washer against the middle bearing centre race. The worm drive is then hard against the centre race of the middle bearing. The pulley side bearing centre race is then hard against the worm drive. On the pulley side of the cam, a spacer (No.43) is hard against the pulley side bearing centre race.......So when the silly nut is tightened, the bearings centre races, the worm drive and the spacer are all pulled together....... The pulley side bearing outer race doesn't come into contact with a seat / shoulder IIRC. So....in theory, the whole assembly could possibly be pulled out with the camshaft from the camshaft cover cap side (although IIRC, the housing/seat for the middle bearing would stop the pulley side bearing from going through the head that way)......It's the cam cap and bearing that keeps it all in place.
AL, I understand your explanation which is once again comprehensive, thanks But, I am still not clear on positoning the pulley side bearing. What happened was: 1. I pressed in the inner bearing - pressing in on its "outer" race. 2. I put the worm gear in from pulley side. 3. I pressed the pulley side bearing in on its "outer" race - when I felt the assy of the inner bearing, worm & pulley side bearing pull up together I stopped pressing in. (I pressed in using a plate with a hole in it, threaded rod, socket & nuts). 4. I dissassembled, put my finger into the inner race of the pulley bearing and it felt notchy when I rotated it. I realised I have pressed the bearing in on its "outer" race in too far and put axial load on the bearing - Hay you live and learn. If I had not pressed it in far enough, when the whole assy was pulled together with the silly nut, this would also put axial load on the bearing by pulling the outer shell into position through the balls. So, I know I have gone round the houses a bit here but my question was how do I position the bearing so I don't but axial load on the bearing either by pushing it in too far, or not far enough. I thought my previous post #11 pressing the bearing in using something that was flat and contacted the the inner and outer race keeping them on the same plane went part way the getting the best result. Your continued input is appreciated. Cheers Gaz
IIRC the inner races project slightly from the outer races..........I accept what you are saying about feeling notchy though; because mine did feel slightly 'notchy' until I ran the engine. I put this down to the pulley side bearing outer race dragging behind in the housing as the centre race gets pushed up tight against the worm gear (or vice versa)..........I think you will find that if you can warm the head, either by running the engine or getting some heat on the bearing housing, the outer race will ease itself into the correct position, even if it is only a few thou that is needed. I pulled the inner bearing in using the outer race of the old bearing and then gave it a few taps on the outer race to make sure it was fully home......I assembled the worm drive etc and then I added the pulley bearing........I tapped a socket on the outer race initially until I knew the centre race had touched the worm gear, then I used a box spanner over the cam against the centre race to make sure it was really tight. Let's face it....if I had got it wrong, I think something serious would have happened inside 10000 miles, which is roughly what I have done since I did the repair to the tacho drive. Try heating the pulley side of the head and see if the outer race eases......or carefully tap the cam on the other end to see if it slackens off.....you might get enough bounce on the centre races to shift the outer race of the pulley bearing out a bit.
AL, Thanks for your reply, I can see you understand the point about the outer race dragging behind or being pushed ahead of the inner race. I did think if you were near enough with its postion then the outer race would find its own position once the temperature was up and the bearings got spinning. I know I may be over thinking this, but just wanted to get the outer race in the best position to start with. I have measured the middle bearing outer and inner and I know you said there was a small difference but thay are both with 0.01mm. I have a socket (the square drive side) that supports both inner and outer. I have ground/lapped this on some wet & dry with wd40 to a very smooth and flat finish. I plan to press the bearing in with this supporting the outer race while pressing in - and when the middle bearing/gear/outer bearing come together it will lock up on the inners, but not push the outer any further into the housing keeping the race grooves inline . I have also fashioned a plastic support ring for the worm gear to get the gear concentric with the bearing inner so it does not drop down and in the wrong position when the bearing inners are pushed together. Thanks AL and all for input. Will try and get some pics when I have the bearings - sad I know. Cheers Gaz
I recommend you don't try to have the tacho drive pinion in place while you are trying to assemble the worm gear on the camshaft with the bearings..........a recipe for a bust tacho drive. PS......No dissing intended, but I reckon you are thinking about it too much...... ....I changed both middle and pulley side bearings; plus the worm gear while the engine was still in the frame and just the fairing and belt covers off...........I hung the oil cooler up out of the way. I had both valve covers off and only needed to remove one rocker (can't recall which one) to be able to pull the camshaft out.......
AL, PS......No dissing intended, but I reckon you are thinking about it too much...... - No problem AL I know my faults, That's why I pointed it out myself before someone else did, and that's why I am 3 years on the renovation. Scared of jumping in and making a mistake, rather than learning from them, anyway enough of my psychological problems . Thanks for your help, I am in a happy place now. Cheers Gaz
