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Laydown gearbox removal

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Can the gearbox be removed from a 1956 Dominator 99 without having to remove the gearbox and engine as a unit ? I.e. leave the engine in position.

I am just thinking ahead as the neutral position is nigh impossible to find and when stationary second gear gets stuck and to free it I have to rock the bike forwards and back. Also the gear change is somewhat notchy. Is this a characteristic of the laydown box ? Other than that the bike is running fine and I am getting to grips in starting it. 

I dread traffic lights and T junctions as I don’t like sitting there stationary with the clutch lever held in.

George

 

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hello yes just take out the left side rear engine plate  , you have too remove rear chain and primary chain case and clutch , then turn so the box come out on the right side   with the right side engine plate in situe , then return it the same way      yours   anna j 

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Hi, from your description it sounds more like a clutch problem to me, has this problem just started?

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The laydown gearbox was regarded as probably the best in the era, known for it's slick and fast operation. Finding neutral can be a problem even on brand new bikes, but it should be reasonable easy to do on a Norton. The usual practice, as far as I know is to remove engine and gearbox as a unit. Problem is the lower bolt holding the gearbox, which is between the frame tubes on a featherbed. With some modifications, I can remove the gearbox on the Manx with engine still in frame, but that involves tilting the engine. An experienced mechanic can do most gearbox work with the gearbox in situ. But for most of us it is much easier to work with the gearbox removed. The NOC shop sells a video on gearbox servicing, which is highly recommended.

Thanks for the replies. I have not had the 99 for long and I have only done 250 miles total. The box has been problematic since my first short run of discovery.

There does seem to be a slight clutch drag - perhaps more of a sensation . I noticed last night on my return that when stationary and in gear that the bike was not totally free when pushing the bike with the clutch lever fully back. So perhaps the clutch should be investigated first before I delve into the box. When the clutch lever is fully back with the bike in gear, is it normal to feel a slight resistance or should it be totally free. I appreciate that this is an ideal or is a slight drag normal ?

George

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Further to my earlier note, I have now tied the clutch lever back , engaged first gear and lifted the rear wheel clear of the floor and the wheel is not completely free to rotate. There is to me clear evidence of some clutch drag. Not sure if this is normal though, although I would have thought that the rear wheel should be totally free.

George

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Clutch drag and difficulty in finding neutral are generally caused by either worn bearings, a worn thrust washer or the mainshaft nut becoming loose. With any of these issues,  pulling in the clutch lever just results in the clutch body moving but the plates hardly separating.

Remove the primary outer case and primary chain and then examine the clutch basket/body. Push and pull the body to check for any lateral play along the mainshaft. If there is any movement or clicking then remove the pressure plate and see if the mainshaft nut has come loose. If this is still tight but the clutch body still moves then the problem is most likely to be wear in the large sleeve gear bearing or the thrust washer on the other side of this gear. Which unfortunately means a gearbox strip to replace.

I used to service many  AMC gearboxes while they were still in the frame. But you still have to partially dismantle the primary side to get at the gearbox mainshaft. You can also remove a gearbox by loosening the rear engine plates. This in turn  allows enough space to wiggle the box about to help remove it. 

The complete engine/gearbox can be removed from the frame as a unit. You can even leave the primary drive gear and carbs in place. However, this can only be done if the top gearbox mounting bolt on the left side is shortened and reversed. 

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... the thrust washer is the one immediately to its left in the diagram. But worth changing both when / if you're in there.

Note the roller retaining plate / washer isn't mentioned in the parts book (at least not in mine) but is on the diagram. It's part number A2/319.

In reply to by anna_jeannette_dixon

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In my experience, there's a small diameter bolt at the front of the engine plate which is in  line with the lower frame rails.  I tried to remove this but did not succeed....  I found that I had to take the crank cases out in unit with the box and rear engine plates. 

Paul

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I would suggest that the first thing to do when the primary chain case cover is removed is check that the pressure plate is lifting evenly. whoever was in there last may have screwed the adjusters in different amounts.

Dick

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... so should have the worm drive clutch lifting mechanism and the mushroom headed clutch lifting component. In this clutch, all screws are fully tightened and the lifter should keep the pressure plate even.

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Should....  but you do need to have a balanced set of clutch springs.  When I got mine, I found an amusingly varied lot, junked them in favour of some new ones

 

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