Locked Gearbox on 1200 8v

I dropped it on the left side into thick Staffordshire mud at around 15-20mph trying to avoid other mud.

Luckily Wendy and i muddy but unhurt.


No superficial damage to the bike - levers, bars, lights, footrests etc,  but gear lever was floppy and selection downwards was very hit or miss.

The GRiSO took us 70ml towards home, then, at low speed as i changed in to 2nd in the middle of a junction, the rear wheel locked solid .

@Pete Roper wrote:
    "When you say the gearbox output shaft do you mean the selector shaft or the driveshaft? Did the wheel lock up?"

Yes the output shaft seems locked wheel only rolls about 50cm back or forwards.


@Pete Roper wrote:
   "Sounds serious, and very unusual. Gearboxes are essentially bulletproof. Can you push it with the clutch pulled in? That would indicate a problem in the clutch or engine. The small amount of movement you can get will be simply the backlash in the selector dogs in the box.

   I fear that this is going to be an 'Open it up and have a look' job."

Clutch feels good but does not free the rear wheel.  When i push the bike it stops with a clunk, not the soft spring of compression ;(.

When i bought it the left footrest was bent back 10 degrees and the the left steering stop broken off. So i think it has already been up the road on the left side in the past, but either way the fall today has finished off something in the gear selection mechanism.

Yes i beleive it will require the full Guzzi motorcycle disassembly ritual. So first i need to clear lots and lots of of space.


@Pete Roper wrote:
   "On the Cali 14 that Michael extracted the gearbox from recently there was damage to the preselector arm. In that case it was a breeze block that fell off the back of a builder's truck that bounced up and slammed into rage shift lever. The shock bent the lever but the force bent the preselector arm preventing gear changes.

With yours it sounds like something has actually broken off inside and may of got jammed between a set of gear teeth. If this is the case it'll be very bad news as one or other of the shafts, maybe both, will likely be bent. You'll need to run them up between centres on a lathe and stick a dial gauge on them to determine run out as even if they are slightly bent they're buggered!

You will need to beg, borrow or buy the gearbox splitting tools. Or make a set. But they are pretty vital for separating the cases without damage. I'd send you mine but I really can't risk loosing them and might need them at any time.

I can also supply a second hand box if you wanted, I've got lots of them from bikes I've wrecked. Might be cheaper than rebuilding though."

Useful gearbox pictures from Pete Roper

1) Selector mechanism in place
[You must be registered and logged in to see this image.]

2) Gearbox splitting tools in action.
[You must be registered and logged in to see this image.]

Question
when looking for a CARC gearbox - are there different primary or other ratios across the models and capacities?

Jon

Yes. Norge & 1200 Sport are different. GRiSO & Stelvio share the same ratio's.

Gotta look 'em up....

Look here: [You must be registered and logged in to see this link.]

Thanks beetle so reading that and plowing through other online owners books it seems there are two gearing set ups for 1200s
one for GRiSO 1200 & all Stelvio 1200 (from 2009 to NTX)
the other for Sport 1200  & Norge 1200GT

The GRiSO & Stelvio run a 26/35 primary and the Sport and Norge run a 24/35 ratio primary
This means that if the 1st to 6th gear pairs were the same the Sport and Norge are lower geared.
[You must be registered and logged in to see this image.]

But as those models have higher ratios in 5th and 6th their top gears are almost identical to the GRiSO and Stelvio
So the overall gear ratios mean that Sport and Norge have a wider spread of gears with lower 1st to 4th gears
[You must be registered and logged in to see this image.]

If i have this arse-about-face someone please correct me

So, as i wouldn't mind the first 4 gears being lower i have just bought a 2007 Sport 1200 box for £280 posted.

I hope it fits

I've got a sport box in my yellow bike. Is good.

Only the Norge has the higher 5th and 6th ratios I believe.

lcjohnny wrote:

So, as i wouldn't mind the first 4 gears being lower i have just bought a 2007 Sport 1200 box for £280 posted.

I hope it fits

Hang on! If it's a 2007 Sport it'll be a gearbox from a 2V bike. Sorry, won't work. The 2V models still used the venerable twin plate clutch with a deep, wide input boss on the shaft and a different shaft and sealing system in the front case of the box.

Sorry. If it's from a 2V bike it's useless to you. You need one from an 8V model.

[You must be registered and logged in to see this image.]
Thanks Pete.
Actually they quote this bike as a 2008 pictures above

What years of Sport at are the 4v head?

2008 onwards. But here at least there were some 2008 plated 2V's as well.

2V input shaft. Note boss for twin plate clutch and shock absorber assembly on input shaft.

[You must be registered and logged in to see this image.]

8V input shaft. No boss, just splined shaft and a surface below the splines on which the seal runs and absence of a shock absorber.

[You must be registered and logged in to see this image.]

So picture 1 on my post
Looks like a 4 valve input shaft?

Didn't see the pics before. Yup. That looks like the correct unit. Phew!

Another giveaway is the colour. I think all the 2V sports had silver cases for engine, gearbox and bevelbox.

It turned out the gearbox was from a 2009 1200 sport and fitted straight on.

Gearchange is crisper (for a Guzzi) than the old box and the lower gearing makes a difference in 1st and 2nd, it is more lively off the line and i prefer that. Just got some cosmetic sfuff to do now.

UPDATE

@Pete Roper wrote:"With yours it sounds like something has actually broken off inside and may of got jammed between a set of gear teeth."

Yep you are right

I took the old box apart today - i did it with a copper hammer and a brass drift rather than properly, as (correctly it turns out) i reasoned that most of the useful parts would be beyond safe or sensible use.

It appears that the forced change of falling to the left at 10-15mph tore the "fixing pin" GUO5234931 that centres the selector mechanism out of the gearbox casting.
After which it bounced around the gearbox and suffered a bit of informal "machining" between the gears.

Looking at the depth of the gouges and cuts in the pin i surmise that most of the gears and shafts are probably cracked, stressed or bent and not re-usable.

Where the "fixing pin" should be
[You must be registered and logged in to see this image.]


My gear box no longer has a pin there
[You must be registered and logged in to see this image.]


Where the fixing pin ended up
[You must be registered and logged in to see this image.]


An informally "machined"  "fixing pin"
[You must be registered and logged in to see this image.]

This gearbox whined in 4th before it locked up but if anyone wants any of the gearbox as spares please say or I will scrap them at the end of January.

Nice bit of detective work Jon & thanks for posting

.....I get the uncertainty of the whizzy bits especially as it locked out, & as it's a big bit of metal; but since my V65 gearbox was happy after completely chewing through a couple of broken washers without any apparent problems (yet ...!), I wonder if it's OK.......either way it'll likely be a 'we'll never know' question.

Well it may be good in parts. But as Pete said i would need to check the shafts for truth between centres and  given the way that the pin had been sliced between the gears i would like to x-ray the gears for cracks.

But another point is that that gearbox always whined in 4th. Really loudly at times other riders could hear it,  it was almost like a siren lol

A very odd failure. Given how reliable they are and the number of scrapped 8V's out there due to the flat tappet issue a replacement should be cheap and easy enough to source.

(Edit.) Just re-read the entire thread and see you got a replacement box.

Nice work Jon. Truly impressive seeing you work through this with some help here.
Hope you plan to keep her and stay in the ghetto.

Hi John
Had a bit of bad luck with my GRiSO, firstly a failed ecu then this.
I think that has weakend my emotional bond with her.
As both incidents occured with Wendy on the back - and she realises how messy the locked gearbox could have been..... She no longer trusts it.

Therefore when i finish tidying up some bits on it and get a new rear tyre I will be selling it on

But i intend to stay around the ghetto.