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Dneprmatic gearbox missing 4th gear


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#1 smoothmachines

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Posted 18 February 2017 - 10:48 AM

Hi, how on earth does my gearbox misses the 4th gear?
It is not adjustable and i´d very much like to keep the semi-automatic clutch feature.
1-2-3 and reverse, all go normally.
But then when shifting into 4th, nothing, or more like neutral.
Then shift down, to 3rd, no problem.
Has someone taken out the whole power plant and has been stealing gears out of my box?
Could it be worn forks or something?
I do have a complete, well working 4 speeds gearbox without reverse, are the gears the same?
My engine is a Dnepr 650CC MT9
Thanks!

#2 Solly

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Posted 18 February 2017 - 10:53 PM

Does it feel like it actually latches in ( detents index ) or the shifter just doesnt move anymore?? Could be the selector plate has cracked or the shift fork has an issue. Either way disassembly will probably be necessary. Not as hard as it seems.

#3 jim.mt10

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Posted 19 February 2017 - 05:55 AM

I would take a quick look inside the gearbox before running too much
in case a woodriff key has fallen out and is in there somewhere.
  Good luck
    Jim

#4 luca.stere

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Posted 19 February 2017 - 10:09 AM

View Postjim.mt10, on 19 February 2017 - 05:55 AM, said:

I would take a quick look inside the gearbox before running too much
in case a woodriff key has fallen out and is in there somewhere.
  Good luck
Jim

The third gear is running, so it is not a woodruff key.

#5 jim.mt10

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Posted 19 February 2017 - 02:42 PM

Good point, Luca.
   Jim

#6 smoothmachines

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Posted 21 February 2017 - 01:29 PM

That´s good, chewing a woodruff key with the gears is a dumb thing to do. I guess i will have to take it apart. I have a MT9 in a Ural 650 frame and the Dneprmatic box, the assy is very long så i will have to hoist the complete power plant out of the frame, and then come back. Lucky i am to have an extra 4 speed box...

#7 razorlight

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Posted 21 February 2017 - 03:52 PM

I had a 3rd gear selection problem with my K650. I took the gearbox off and opened it up. Turned out to be a worn shift fork. Working fine now.
1970 Dnepr K650 and sidecar
England

#8 smoothmachines

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Posted 22 February 2017 - 09:28 AM

The box is a MT804 btw. I´ve read about worn forks, thank you Razorlight, it said that as the movement is very small, 5mm, it would not take much of wear to render the shifting impossible.
The box is anyway leaking and i will even check overall wear. Fork set costs 35 euros or 40$, as well as for the bearings,  and there are many other components that could be worn. A NOS box is 360 Euros, could be a better choice if many parts are worn and not easy to fabricate at the shop...

#9 Solly

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Posted 01 March 2017 - 10:17 PM

Seeing as how you said the unit is leaking. If you decide to repair it. Dont assume its leaking from a seal. Mine turned out to have a spot of porosity near the shift shaft boss.

#10 harleych

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Posted 02 March 2017 - 01:24 AM

Any way need open the box. Don,t  mix fork shaft and second shaft looks the same....they are different lenght.

#11 smoothmachines

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Posted 02 March 2017 - 08:35 AM

Leaking through pores, that seems to happen now and then, poor metallurgy. Did you repair that?

#12 Solly

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Posted 02 March 2017 - 11:03 PM

Yes. Though it was considered a challenge by the welder that heli arc it. Because of the thickness of the wall and causing a collateral problem with the bore that the shift shaft travelled through.

#13 sallen

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Posted 03 March 2017 - 08:52 PM

Had the same problem with my Dnepr, shifter plate pin for forth gear broke off.
You're going to have to open the transmission.

#14 Serious Black

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Posted 08 March 2017 - 09:55 AM

Brit owners seal porous castings by painting them on the inside with epoxy based paint.
The devil is in the detail.

#15 Solly

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Posted 10 March 2017 - 10:17 PM

Not sure if epoxy paint would hold up in long run to standard Gl 5 gear lube or any non synthetic gear lube. Given the amount of sulphur in it.The test of time would be intetesting.It does eventually soften and lift on a garage shop floor if in continuos contact.




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