Author Topic: Gearbox rebuild  (Read 331 times)

Offline JHG1958

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Gearbox rebuild
« on: 15.02. 2020 17:57 »
Having assembled my gearbox putting the inner cover in place, I was surprised I could not turn the mainshaft by hand.  Is this normal. Or have I made a cock up around reassembly
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Online muskrat

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Re: Gearbox rebuild
« Reply #1 on: 15.02. 2020 19:11 »
G'day John.
Is the box in the frame and primary (clutch & chain) attached? If it is the mainshaft wants to turn the motor over and will not spin by hand. If the box is out of bike the main shaft should spin.
Cheers
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'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
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Offline JHG1958

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Re: Gearbox rebuild
« Reply #2 on: 15.02. 2020 20:20 »
No the box is still on the bench.  Outer is still off.  I was expecting it to turn easily
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Online muskrat

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Re: Gearbox rebuild
« Reply #3 on: 15.02. 2020 21:57 »
G'day John.
If all is good inside it should turn. How far down did you strip it and what parts/bushes/bearings were replaced? Is the quadrant indexed correctly? Could be stuck between gears.
Cheers
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Offline JHG1958

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Re: Gearbox rebuild
« Reply #4 on: 16.02. 2020 08:10 »
Hi Musky

I feared so. It was a complete strip down with new bearings and bushes.  The layshaft and main shaft turned nicely. I will take off the inner cover and see what the matter is. At least I know what I am doing today. 

Thanks for the advice. I will confess the error of my way when I have found out what I have done. At least I knew when to stop.

John
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Offline Swarfcut

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Re: Gearbox rebuild
« Reply #5 on: 16.02. 2020 10:10 »
Just a thought....

   Check the thrust washer 67-3202 (between the layshaft shoulder and first gear cog) is fitted with the internal chamfer towards the clutch side. This clears the radius where the layshaft diameter changes.

     The mainshaft is supported on ball races, the one in the inner cover provides the lateral location, so the mainshaft should never bind, unless it is too tight in the output gear sleeve. This can't be said of the layshaft, which runs in bronze bushes, both with a top hat flange.
     As you have changed these it is possible the  top hats are slightly thicker than the originals and with the inner cover tightened down the layshaft and its gears are being clamped tight. So see if the layshaft alone is binding. See if it still binds with the steel washer removed.  If all is now free, check the layshaft pinion is pressed on fully to the locating circlip. With no wiggle room here the washer or the face of the inner cover bush needs to be relieved to provide an axial running clearance for the layshaft. This washer controls the layshaft end float, which should be minimal.

 Swarfy.
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Offline JHG1958

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Re: Gearbox rebuild
« Reply #6 on: 16.02. 2020 19:30 »
Success in more ways than one. 

Somehow the gear selector had moved off neutral. Probably the main problem was too much pressure by the single retaining screw without the joint being fully closed.

When I took it apart I realised that the oil hole in the layshaft bush on the inner cover was not aligned with hole in the casing.  Close call.  Bush removed and refitted correctly. Layshaft float is fine and now nicely boxed up.  The main shaft was really tight on the bearing and I had to heat the inner cover to get it to fit easily.  I cannot put the outer cover on yet as I am getting the clutch actuator rechromed. 

Incidentally. The Haynes manual suggest putting gasket cement along with the gasket.  On advice from An engineer I have not put any on. What do others do?

Also I polished the outer cover but I see it’s starting to corrode. What people do, keep polishing or varnish?

John

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Re: Gearbox rebuild
« Reply #7 on: 19.02. 2020 09:49 »
G'day John.
Ho-ray it was a simple fix. Yes that bearing is a snug fit. I use Permatex #3 non hardening sealant on most gaskets. Most of the time the gaskets can be re-used (must be my Scottish heritage!).
Cheers
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Online Slymo

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Re: Gearbox rebuild
« Reply #8 on: 24.03. 2020 00:55 »
I used Flexoid gaskets dry on mine. Need a tighten up after a few days but dry as a bone and no problems with re use.
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