GS750 77-79 Possible to open the gearbox whitout removing the topend/cylinder?

[gsman]

Hi!

I have a engine that maybe need some attention when it comes
to the gearbox as it feels like it has a lot of freeplay in the gears.
As it is lot of secondhand complete gearsets availabline on Ebay
I was just wondering if it is possible to just lift the bottom half
on the gearbox off the rest of engine leaving the topend in place
and by that save time dismantling some of the rest.

I have some time ago had the engine in bits and pieces
and as I have already a good topend in place I asking if
this is possible.

To me it seems that the only issue doing it this way
could bee engaging the camchain sliders into the bottom end.
I know this because when I last time assembled the bottomcases,
I just mounted the crankshaft and gearaxles in the upperhalf
enginecase and finally with the upper enginecase upsidedown
lovered the bottom half in place closing it before mounting the bottompan and
the rest of engine.

Some of you have doing this or or other work on the gears
whithout removing the topend/cylinderjugs?


In advance,
Thanks.

gsman

[Agemax]

you can do it, but you will have to remove camshafts and camchain guides, then refit them after the cases are back together.

[gsman]

But will I get to the 8mm camchain tensioner sleevebolt in the down back of the cylinder using a long socket extension
as it seems to be blocked when the cylinder is mounted?

[Agemax]

you dont need to remove the rear blade, just the front one that locates into a guide, which is bolted to the bottom crankcase.
the rear blade is bolted to the top case.

[Guest]

It's pretty hard to imagine how the amount of lash in the gears could be increased much by wear, considering the amount that is already in there from the engaging dogs. Unless you have a known good one to compare to you may be imagining a problem that isn't there. Excess drivetrain lash is usually related to chain wear or worn/rotted cush hub rubbers. If the gears are worn enough to cause more lash I'd think you'd be hearing some loud noises.

I'm not sure exactly what you mean by 'free play'.

On some motors you can get somewhat of a look at the gears by removing the sump.

[gsman]

Yes,it is definitely a liitle noisy,the bearings when checked last time box was opened and
was feeling smooth,no roughness.Can the bearings for the counter and driveshaft then be very noise when
they are feeling smooth?
The freeplay that I talk about
is when I hold the clutch axle with one hand and when any gear
selected and try to move the engine drive sprocket back and forth.
I hear a very clear "click-clack" sound when doing it so.
From other bikes doing this test the feel have been very direct
by when selecting a gear there have been no back and forth
lash movement and no clicking sound either.

Some opinions on this?

gsman

[tkent02]

Ride it.

[londonboards]

I was worried about that once. Even made a vid about it. But it's normal. Pretty indestructible all round. I'm holding the sprocket with my knee:

[TeamDar]

The narrator is mistaken about what gear he is engaging. He says first gear when he engages second. And says second gear when he engages first. The backlash is normal due to the dogs and slot engagement. Normal for a constant mesh gearbox. Dar

[geol]

Dar, The gears reverse function when the engine is upside down I think. BTW: Good catch... most folks just notice the slop and not the direction shift drum rotated.

[gsman]

Thanks for all the input on this topic.
Think my brain is sorted about the gears function
and noise for now.

gsman