Removing Gearbox

Oakland850 · Dec 26, 2012

Hi Everyone - hope you all had a great Christmas! One question - I have to remove the gearbox from my 1974 850 to re-build. Do you have to remove the entire primary case ( meaning inner and outer) or can you just remove the outer, clutch. primary chain and drive chain? Also, Do you have to remove the center-stand for clearance? Thanks guys! :?:

nortonspeed · Dec 26, 2012

Yes you will have to remove the complete primary case. Centre stand can stay though.

swooshdave · Dec 26, 2012

Doesn't he have to loosen the engine too?

nortonspeed · Dec 27, 2012

swooshdave said:
Doesn't he have to loosen the engine too?

Indeed he will have to tilt the engine backwards (over the top engine/cradle bolt) to clear the bottom cradle gap to gain access for the gearbox shell.

Oakland850 · Dec 27, 2012

Thanks for your advice - So I guess since the engine has to be tilted, removing the exhuast as a first step is required. Also, if I wanted to make my own engine sprocket puller, does anyone know what length and Whitworth thread bolts are required for the sproket? The real tool part number is 064297 as per the shop manual. :?:

L.A.B. · Dec 27, 2012

Oakland850 said:
Also, if I wanted to make my own engine sprocket puller, does anyone know what length and Whitworth thread bolts are required for the sproket? The real tool part number is 064297 as per the shop manual.

The engine sprocket extractor thread should be 5/16" UNF, not Whitworth. The bolt length will ultimately depend on the thickness extractor 'plate' or 'beam' used, the bolts supplied as part of my 064297 extractor are 4 inches long.

Hobot · Dec 27, 2012

Definitely put some good heat on the crank sprocket before trying to apply full torque on the puller as I've had two pullers break when I didn't, one a wimpy steering wheel puller and the other a big fat robust puller built similar to the factory over built kind. Steering wheel puller broke on tightening, the other just snapped while looking at it waiting for heat to hit. No I didn't hit puller with flame.

On Peel Combat with the low breather baffle removed to TS case, all I had to do was tip g-box forward CW to slip it right out. On Trixie Combat with the low baffle in place, I had to remove stuff to tip engine forward to clear the baffle to remove gb. I've done this bike on center stand or hung by sky hook, and bike didn't fall in half.

DogT · Dec 27, 2012

Didn't I see someone use the foot peg where it mounts on the z plate as a puller for the sprocket? Or was that for something else?

Dave
69S

Madnorton · Dec 30, 2012

May come without tipping the engine on a pre-MKIII. Mine, on my MKIII came out easier than expected though it makes good sense to loosen the engine mountings and re-tighten checking isolastics and alignment as you re-assemble.

acotrel · Dec 30, 2012

If I have to pull a big sprocket off a taper, I usually tighten the puller up until it has some stretch in it then give the centre bolt one sharp tap with a hammer. I don't use heat unless I suspect some idiot has used loctite on the taper.

DogT · Dec 30, 2012

For me the heat from a heat gun works pretty good. At least the last time, I put some tension on the puller, gave it about 3 minutes of heat and it popped right off, and it was my installation, no locktite. No whacking on the end of the crank either. But it had been off within the last year too.

Dave
69S

rwalker28 · Dec 31, 2012

Does anyone have a drawing of how to modify the cradle so one doesn't have to tear the bike apart to remove the gearbox? '74 Cdo in particular.

dero · Dec 31, 2012

I would like that info too , if anybody has it .

bwolfie · Dec 31, 2012

Upper left corner, this is the alloy cradle I made, you will see an area that has been notched out. This allows the transmission enough clearance to be removed. I think it is about an inch worth.

Here is how the opening looked before for reference.

dero · Dec 31, 2012

Thank you .

rwalker28 · Dec 31, 2012

Nice, thank you very much.

Removing Gearbox

Oakland850

nortonspeed

Guest

swooshdave

nortonspeed

Guest

Oakland850

L.A.B.

Moderator

Hobot

DogT

Madnorton

acotrel

DogT

rwalker28

dero

bwolfie

dero

rwalker28

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