1975 3 1/2 Sport

[Morinimatt]

Hello

I am posting in the projects as this is a project for me. My dad passed away a few months ago, i got left his 1975 3 /12 sport.

It was his dream bike but broke down every time he rode it. He had it 10 years before passing away but im not sure what maintenance he did to it.

So far i have rebuilt the carbs and i gave the fuel tank a swill out and filled with 98 ron. It fire up straight away but instantly began screaming like the throttle was stuck wide open even though its not (i have attached a video) the second time i started it it ticked over nicely for around 30 seconds before it started revving up again.

I really need some advice on how to sort it. Im pretty mechanical but carbs are something ive never worked with, i assume theres a problem with the air fuel ratio but like i said im stuck.

I also dont know the condition of the timing belt so dont want to be having to start it too much till ive checked that out. Cheers Matt


https://flic.kr/s/aHBqjACiCd

[morini_tom]

Hi Matt,

Firstly sorry for your loss.

Initial question on the carbs- are the slides in the correct way round as it’s possible to fit them backwards. Cable should enter the carb top on the engine side of the card and then rim un straight down to where it hooks into the slide, again, on the engine side do the carb.

Next, are the throttle cables hanging up? If they pull out of the carb top or twistgrip housing they can sit on top of the adjuster rather than in it. There should be some initial slack in the throttle cables.

Finally, ensure you’ve got no air leaks. Split rubber manifolds between the carb and engine, or if you still have the original metal intake manifolds then leaks from any of the joints is possible.if you can get the engine idling, spray some coldstart or similar in the vicinity of the manifolds and if you have an air leak it’ll get sucked in and you’ll get a momentary change in engine speed.

Regarding the belt, yes definitely change it. It’s easy to do and cheap enough.

Check out Paul Compton’s videos on YouTube (search Paul compton Morini)- you’ll find a lot of useful how to videos which he’s done over the years.

Morinis are very reliable and rewarding when sorted. There’s a wealth of knowledge in the club to help with that. Whereabouts are you based? We’ve got members and sections dotted all over.

Tom

[norbert]

To me that sounds a lot like air leaks concerning the rubber manifold head-carburator. Test it like Tom says with breake cleaner spray or something like this. When it is running at high revs at idle try to press the carbs towards the head or just moving their position a bit. When revs are changing, doing this > air leaks.

[Morinimatt]

Thank you for your replies i will definitely look into those bits. Could it also have anything to do with the setup of the carbs? As im struggling to find a source of info to get them ideally set up.

[Daddy Dom]

Here be carb settings.
https://www.motomoriniclub.nl/carb.html

[Morinimatt]

Hi everyone

Thankyou all for your help so far I think i sourced my carb issues to the rubbers which i found from a gentleman in ireland.

Next up is the fuses, from what i can find they are ceramic continental fuses? But i have no idea ive never seen these before im guessing its the reason i have no tach or lights etc. If anyone has some info it would be greatly appreciated.

Thanks

20231028_095000.jpg (377.25 KiB) Viewed 11402 times

[Morinimatt]

Also based in West Yorkshire so if anyone knows where is a good local source for parts etc that would be a great help

[morini_tom]

Sadly local decent automotive factors are becoming a thing of the past. Nowhere near me so I bought my last lot of fuses from EBay.

If you search for ‘automotive bullet fuse’ you’ll find what you need.

The fuses in the fuse holder should be tight. Often these go sloppy over time which doesn’t help with electrical gremlins. You can bend them a little to restore some spring, but when they get to that stage I tend to take the whole fusebox apart as if they are loose there then normally the rivet joints behind the spades are also loose or corroded too.

Best solution is to disassemble the whole fusebox by drilling the rivets out, cleaning up, then re riveting (or bolting with appropriate locking nuts and epoxy to stop them coming undone) and if you really want belt and braces, soldering the joined terminals too.

With the above job done properly now you’ll probably never have to think about it or check electrical conductivity in there again

[dunk 1]

My local Halfords used to have them when I last needed some - it was the easiest option where I live- they still have them to order in - type in continental fuses
Duncan

[Morinimatt]

Thanks for your help, ended up getting same (but in a different metal) and i have working ancillaries now.

Just get her running right and new tyres and shes ready for a ride.

[Morinimatt]

Im back! Update is dads Morini was in storage with a friend while i was building my house, im now on with the rebuild, cam belt and oil change is done.

Spent this weekend stripping and ultrasonic cleaning the carbs, catalogging whats knackered and beginning to order everything.

Im going to try and eliminate all possible issues, had a stubborn carb trumpet which i put into the vice with soft jaws it just crumbled like a piece of stale bread.

If i can firgure out how to upload photos (its saying they're too high mb to upload?) Ill do that as i go cheers

Matt

[Morinimatt]

Worked it out

[morini_tom]

The crumbling carb trumpets on the early carbs is sadly quite common. They are made of zamak or similar which seems to corrode and crumble over time almost without fail. My advice is to replace them with the plastic trumpets from the later carbs- a straight swap- before the engine ingests a wayward chunk.

[Morinimatt]

I have got them on my order list, it mustve happened on one previously as the other already has a plastic one