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Fitting A Tachometer Gear To A 1994 Monster Engine

Discussion in 'Technical Help' started by Geoffrey Lebowski, May 12, 2020.

  1. I have a 1994 Monster engine that is being used in my Spondon build.
    The 94 Monster did not have a tacho, but had the front head machined to take one with a blanking plug. A spacer was fitted in place of the tachometer worm drive gear on the camshaft.

    I have the gears to fit to the engine which I think came from a 906 Paso, and a nice period whiteface Veglia tachometer.
    My question is can you remove the spacer and substitute the worm gear on the camshaft without removing the cylinder head and the camshaft. It looks like the oil seal would need to be replaced, but I don't want to rip it out and then find I can't remove the spacer without removing the camshaft, which I'd rathe avoid if possible. IMG_0221.JPG IMG_0222.JPG
     
  2. You will definitely have to remove the camshaft. Behind the seal is a bearing, then the worm gear, then another bearing. So the gear goes between the bearings and you will have to take at least one of them out to fit it. See the attached drawing from the parts list.
    A few years ago I was fitting ST2 heads to my 907ie and had to have the horiz head machined to take the tacho drive. Fortunately the head was already off the bike which made it much easier.

    Screen Shot 2020-05-12 at 20.45.09.png
     
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  3. Thanks Derek,
    Which engine is that? I was going off the 750 Paso parts manual which seems to show the worm gear (item 41) between the seal (item 42) and the outer bearing (item 40).

    upload_2020-5-12_22-49-34.png

    In your opinion, can the camshaft be removed with the head in situ, or is it best to remove the head?
     
  4. Taking a look at the Stein Dinse parts fisches, the ‘94 Monster 900 and ‘92 900SS are both shown with the spacer/ tacho drive Outside the bearing, with oil seal and bush outside it. The only difference between the assemblies is the substitution of the spacer for gear.

    The camshafts are the same part number.

    https://www.stein-dinse.biz/eliste/index.php

    Having not taken one out, I don't know whether the bush slides out easily, or whether it needs the camshaft to be driven out of it?
     
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  5. I have done this job with the engine in-situ (750 SS)......I had to replace the actual worm gear which had broken up. It wasn't too hard, but you have to be careful.

    There is a good chance the oil seal can be picked out and then the bush can also be picked out....the shorter bush in mine slid off fairly easily, even though it seemed as though water had got in and created a rust film under the bush.

    There is a good chance the woodruff key won't be present.....

    ......Ducati stopped fitting them at some stage, but the keyway in the cam shaft will probably exist.

    Ducati relied upon the whole assembly being done up tight to stop the worm gear from slipping (it it probably why mine had broken up....ie, the silly nut not being tight enough).

    Once the reassembly is done, just make sure that silly nut is bloody tight and bloody bloody tight.

    One point I can't answer..........will the actual gearing be correct?

    AL
     
  6. It was 4 or 5 years ago when I had the 907 heads apart and I honestly can't remember now the exact location of the worm gear but I've been looking through the various parts lists I have and some of them show the spacer/gear between the bearings and on others, outside the bearings between the outer bearing and the spacer that goes under the seal - even for the same model!
    I have noticed this sort of thing before; you can't depend on the parts list for showing the location and/or orientation of some parts.
     
  7. Yes, you are correct Derek.......I just had to go back and look at the information and photos when I did mine.

    The worm gear was between the pulley side bearing and the 'middle' bearing.....although I managed to move the pulley side bearing off it's seat, because of the amount of metal particles in the bearing, I decided to take the cam out so I could replace all the bearings if necessary.

    The cam cover bearing was OK, but the pulley side and the middle one were well buggered up with metal bits, so they got changed.
     
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  8. Thanks for all your help guys.
    I managed to remove the camshaft with the head in situ.
    I removed the outer oil seal and yes there was a bearing (item 14) before the spacer (item 4). As mentioned parts manual not correct in the relative positions of components.
    Slid the closing rockers sideways and was then able to slide the cam out past the rockers by rotating it.
    Slid the spacer down and used a fine drift to carefully tap out the bearing on it's outer race.
    Was then able to remove the spacer.

    Just need a new seal, gasket and silly nut to reassemble with the tacho gear in place of the spacer. No keyways, so I'm thinking of adding some bearing fit when assembling to minimise the chance of it spinning on the shaft.

    cam tacho drive.jpg
     
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  9. Thanks for the feedback
     
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  10. Good idea using Loctite bearing fit. I did exactly the same thing, but you have to work fast finishing the assembly and getting that silly nut really tight.
     
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