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1974 3 1/2, gearbox issues

Posted: 24 Jun 2025 15:34
by OlyMoto
I've fetched a mostly complete and running '74 3 1/2, with known gearbox issues. I asked about this bike a while back prior to purchasing, not knowing any real details of the gearbox and inquiring about parts availability. Given it sounds like most anything could be addressed and the price was right, it now sits in the garage awaiting next steps. Since the engine needs to come out to address the gearbox issue, I'm considering a full resto on it.

RE the gearbox issue - perhaps it will be obvious once opened up, but given there's a significant gap in my knowledge of such things, I thought I'd query the MM brain trust here now that I've ridden it and can provide a much clearer description of the issue.

In short - it's near impossible to keep the bike in third gear. It shifts into it, and if you baby the throttle and are essentially putting zero load on things, it will stay there long enough to shift to 4th. Mostly though, you need to shift from 2nd to 4th right away as 3rd is useless.

It does not permanently pop out, i.e. into a false neutral. Rather, it will rapidly go in/out of third gear every couple of seconds. I only did this a couple of times, not wanting to cause further damage - but perhaps that description narrows down potential issues?

Thanks in advance. I'll document the repair and eventual restoration as it take place.

Image

Re: 1974 3 1/2, gearbox issues

Posted: 24 Jun 2025 15:53
by MickeyMoto
Don't ride it until fixed. If a part is broken, if it breaks it will lock the rear wheel. The gearbox is not hard. Look at the selector forks, inspect the teeth and also check the bushes. I had a gearbox where the bushes were worn. Still changed gear ok. The selector mechanism can be a problem on reassembly.

Re: 1974 3 1/2, gearbox issues

Posted: 25 Jun 2025 09:53
by George 350
Early motors had weak (aluminium?) selector forks. These wear and can give symptoms like you describe.
Cure is later model selector forks, or complete fork and drum assembly. Part numbers from parts book will guide you to what is and isn't interchangeable, but ask first if in any doubt.

As has been said, please fix it before you ride it again.

There are other weak areas on the first motors too. Big end bolts and rocker pillar studs were improved on later models so be very careful on tightening these.
Hope that this helps,
George

Re: 1974 3 1/2, gearbox issues

Posted: 25 Jun 2025 10:36
by George 350
WARNING!
If/when you strip it, DO NOT remove the spring hook plate from the crankcases unless you have access to the special tool to realign it properly. If not correctly aligned, you might not get all the gears, or you might be able to change up but not down. Get it wrong and it does mean a full strip down to reset it. I have got the T-shirt for this!
The Cagiva era manual does have a lot more info on this item regarding alignment, but without the tool ( or an old cutaway case half) it can be very difficult to get right.
Regards,
George

Re: 1974 3 1/2, gearbox issues

Posted: 25 Jun 2025 12:34
by Morini Jen
The special tool George referred to is Morini Special Tool 008. Attached are some images from 'The Blue Book' which can be downloaded from the Club Library if you are a member.

Changing the subject briefly... Obviously the gearbox issues are your priority, but if you are still looking for some top quality side panels, the ones I have for sale are the correct ones for your bike.

viewtopic.php?f=5&t=8068

Good luck.

Re: 1974 3 1/2, gearbox issues

Posted: 25 Jun 2025 16:40
by OlyMoto
Thanks all for the great info! Much appreciated.
Morini Jen wrote: 25 Jun 2025 12:34 The special tool George referred to is Morini Special Tool 008. Attached are some images from 'The Blue Book' which can be downloaded from the Club Library if you are a member.
Yep, I'm a member and have a printed manual on the way as well.

Is this special tool still available anywhere, either for purchase, rental or loan?

Re: 1974 3 1/2, gearbox issues

Posted: 25 Jun 2025 16:58
by Steve Brown
I bought mine from Soren in Denmark. (there should be an accent above the O in his name) His version is a simplified but good, simple plate rather than a cut away crankcase. Hopefully he can be contacted via a search on here, or look for his youtube videos, he has done a few very useful videos about Morini head scratchers.

Re: 1974 3 1/2, gearbox issues

Posted: 25 Jun 2025 17:43
by OlyMoto
Steve Brown wrote: 25 Jun 2025 16:58 I bought mine from Soren in Denmark. (there should be an accent above the O in his name) His version is a simplified but good, simple plate rather than a cut away crankcase. Hopefully he can be contacted via a search on here, or look for his youtube videos, he has done a few very useful videos about Morini head scratchers.
Thanks for the tip! I found his YT channel and an email contact there. Link for others searching:

https://www.youtube.com/@Sir1HH

Re: 1974 3 1/2, gearbox issues

Posted: 25 Jun 2025 18:24
by George 350
I wonder, if Soren has a drawing, that could be converted and made by 3D printing? It doesn't have to be too strong, just have holes in the right places.
This would help people like the original poster who is unlikely to have much in the way of local support get the tool much more easily.
Just a thought.
George.

Re: 1974 3 1/2, gearbox issues

Posted: 25 Jun 2025 20:08
by OlyMoto
George 350 wrote: 25 Jun 2025 18:24 I wonder, if Soren has a drawing, that could be converted and made by 3D printing? It doesn't have to be too strong, just have holes in the right places.
This would help people like the original poster who is unlikely to have much in the way of local support get the tool much more easily.
Just a thought.
George.
I'll ask him assuming he replies, George.

And, if anyone does have one they could part with for a bit - I've a very talented friend who could duplicate it and 3D print one for me. He's done far more difficult designs. We'd share the design files if anyone is so inclined to loan one out, and I'd be happy to pay shipping to and from if anyone is willing.

Will

Re: 1974 3 1/2, gearbox issues

Posted: 25 Jun 2025 20:36
by Morini Jen
Hey there George 350 and OlyMoto...

That's the spirit!.. :D

People helping each other out.. I love it!

Forza Morini!