Gearbox problems

[Baldini]

Haven't seen one break there before. They usually go at 90degree bend. Everything else in order?

 

KB

[Richard]

Everything else is ok (I hope....). sorry about the poor position of the bits in the photo. the broken section is sat as though it would be attached to the spring, the bend to the right is the bend for bracing on the selector arm.

[belfastguzzi]

... position of the bits in the photo. the broken section is sat as though it would be attached to the spring, the bend to the right is the bend for bracing on the selector arm.

At first I thought that was what you intended, but surely it's not right? That bend to the right must be the bend of the broken spring coil. Turn it through 180 degrees.

Like this:

[Richard]

Nope. the broken end fits perfectly. That's what confused me somewhat. I have come to the conclusion that this is not a stock spring. This would also explain why it didn't break in the normal place.

 

Edit:

My mistake, I put the end the wrong way round for the photo!!! This however doesn't explain why it broke in the non standard way......

[belfastguzzi]

I really don't think so.

The bend must be the coil bend. Is that not the 'hook' end that is pointing up towards the camera?

Did you compare it directly against the new spring to see if the short, sharp angled hook bend at the end was the same, or as you seem to be saying, different, on both?

 

Edit: ok – I see your edit.

 

As for non-standard break, well it may be a bit of a lottery as to where exactly it breaks. The thing is that it broke in the section that is stressed when the coil binds. Often the other end of that section breaks – it is stretched more for the sharp bend – but I guess it could break at either bend (at either end of the short section).

I'd still be suspicious that it wasn't a loose enough fit around the boss, somehow there wasn't enough space to allow the full movement that that bit of wire is forced to make.

 

I'd be lookiing carefully at that boss again – size and shape.

 

On the other hand, maybe there are batches of bad springs with weak wire? ?

[Flatland Dan]

I think Belfast may be right about a batch of springs made from weak wire, because when my spring broke, it was in an identical spot. And for sealant at the mating surfaces, I used Detroit bellhousing gasket sealer. We have torn apart bellhousings after half a million miles and the sealant was still pliable and not leaking.

[Jim in NZ]

Hi folks, I have the same problem as Richard. My bike stuck in first gear last weekend and stranded me 200 km from home. The shift return spring has broken, about in the middle if you imagine the whole spring stretched out straight.

 

My bike is an '04 Coppa Italia. I have done 21,000-odd km from new, and this is the first breakage. The spring boss is 15mm diameter, and the spring coils are 16.8mm inside diameter, so from opinions in previous threads on this subject, I thought I was safe! The only sign of binding on the spring boss is very near the right-angle bend, but not on the coil that actually broke. Bad spring????

 

The poor sods who were having this problem repeatedly should have built up some experience with these springs by now. My question is, has MG learnt how to make the OE springs properly now, or is there an aftermarket spring which has proven to be better? Perhaps larger diameter coils would be safer.

 

If there is a consensus on an aftermarket spring, a website or email address would be helpful please.

 

This website is a marvellous resource - my grateful thanks to everyone who freely contributes their knowledge. I don't think it would be realistic for me to own a Guzzi more than 3 hrs from the nearest dealer if it were not for your help.

 

Cheers,

Jim.

[MickM]

Hey Jim, my opinion only but I don't think it's the fault of the spring but rather the set-up. You need to eliminate all potential stress risers at contact points and also stop the spring from twisting. This is how I did mine - http://www.v11lemans.com/forums/index.php?...ost&p=37565 Several other guys report a similar approach and I'm pretty confident that it's a comprehensive fix. Good luck .... once you fix the few quirks they're a wonderful bike.

[Jim in NZ]

Thanks Mick. Just waiting for new spring from MI (NZ importers unable to supply, despite MG service bulletin last year on this subject). When I can reassemble the shift mechanism, I will look at the sideways twist that you mention.

I agree it's basically a superb machine, including the fact that you can remove the side of the gearbox to do this job. On most bikes you would have to remove the engine/gearbox and split the crankcases. (We'll just quietly forget that on most bikes you wouldn't have to!)

Cheers,

Jim.

[Dan M]

Hey Jim, my opinion only but I don't think it's the fault of the spring but rather the set-up. You need to eliminate all potential stress risers at contact points and also stop the spring from twisting. This is how I did mine - http://www.v11lemans.com/forums/index.php?...ost&p=37565 Several other guys report a similar approach and I'm pretty confident that it's a comprehensive fix. Good luck .... once you fix the few quirks they're a wonderful bike.

 

 

You are correct Mick, another bit of insurance is to put a slight bend in the long end of the spring to relax the tension. The spring is there to locate the pawl against the pins but does not need to have heavy tension. If you carefully bend the long end back some so the spring is not wound as tight on the upshift, you will greatly reduce stress on the spring. Lessening the tension and polishing all of the contact points on the pawl improves the shift feel and quickens the return as well.

[Zooter]

 

Hey Jim, my opinion only but I don't think it's the fault of the spring but rather the set-up. You need to eliminate all potential stress risers at contact points and also stop the spring from twisting. This is how I did mine - http://www.v11lemans.com/forums/index.php?...ost&p=37565 Several other guys report a similar approach and I'm pretty confident that it's a comprehensive fix. Good luck .... once you fix the few quirks they're a wonderful bike.

You are correct Mick, another bit of insurance is to put a slight bend in the long end of the spring to relax the tension. The spring is there to locate the pawl against the pins but does not need to have heavy tension. If you carefully bend the long end back some so the spring is not wound as tight on the upshift, you will greatly reduce stress on the spring. Lessening the tension and polishing all of the contact points on the pawl improves the shift feel and quickens the return as well.

I have read a few in agreement with adding the 1.5mm shim washers and profiling the pawl to the spring hook. But monkeying with the spring tension is a new one. Without having parts in hand I can't tell if the spring is spread or compressed to bend it for less tension when working.

[docc]

Hmmmm, bending springs. This is surely a black art.

[Zooter]

I know little of metallurgy, but surely bending/unbending spring steel will harden the bent/straightened section.

[docc]

AKA "work hardening?"

 

Worries me that would produce brittleness, fatigue, and failure.

[Zooter]

Precisely, to get it into shape it is cold rolled, after that it may be annealed, or otherwise re-treated for springyness. What I learned of metallurgy wouldn't have filled 5 pages, a long long time ago and never covered spring making.

 

Cold working after the fact can only be bad, but perhaps far less bad than the failing mode of the original!