Difficult 3rd to 4th gear change

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robint
Posts: 103
Joined: 09 May 2006 12:58
Location: Essex, UK

Difficult 3rd to 4th gear change

Post by robint »

Out for a short bimble yesterday and had difficulty going from 3rd to 4th - sometimes.... No problem with going down the box from 4th to 3rd or any other changes and no sign of clutch slip or drag, felt as it has always done. Engine running fine, no odd noises. Any suggestions, presumably will need a strip down (winter project???) to find out what is going on internally.
robint
(Morini, Enfield, Deauville, SLK and home to support)
BumbleBee
Posts: 140
Joined: 13 Jun 2017 21:10
Location: Reading

Re: Difficult 3rd to 4th gear change

Post by BumbleBee »

Some resistance in the mechanism that only does those gears would be the thing for those symptoms. e.g something impeding one of the dog units from sliding on it's shaft or impeding the selector forks moving along the slots in the selector drum. Or similar for the pawls. So that's gunge, wear, burrs, etc even rust if the bike hasn't been used for a while. Although I've also heard people give similar symptoms, not necessarily Morinis, but it turns out to be parts of the external shift mechanism rubbing/hitting casings or the frame, or itself, due to gradual changes/wear and tear sneaking up on them. You would think it would be the same movement in every gear but if the findings of some are to be believed then maybe it's not the same when going between 3-4 ?
huub
Posts: 194
Joined: 24 Jul 2006 15:11

Re: Difficult 3rd to 4th gear change

Post by huub »

pretty typical of gearbox damage , how old is the engine?
early 350 engines had alloy selector forks , which tend to wear out.
robint
Posts: 103
Joined: 09 May 2006 12:58
Location: Essex, UK

Re: Difficult 3rd to 4th gear change

Post by robint »

1978 UK all its life (and part of mine for 37 years!) with 24K miles. Had work done at NLM many years ago to repair the crankcases after finding a previous owner had obviously had chain issues and repaired it with plastic metal and dirty grease....... Never sure everything was realigned correctly, but no problems (not knife thru butter but OK!!) for the last 13K miles till yesterday.

Are gearbox internals readily available from Medina?
robint
(Morini, Enfield, Deauville, SLK and home to support)
mbmm350s
Posts: 666
Joined: 22 Jun 2018 10:18
Location: Reading UK
Location: Berkshire UK

Re: Difficult 3rd to 4th gear change

Post by mbmm350s »

Hi,

can you check if the gearchange with correct revs it should work fine without disengaging the clutch.

Other factors that could affect the smoothness of gearchange probably
you already checked these but certainly worth a double check before stripping engine.

Chain tension and chain wear especially tight spots, or misalignment.
Not so much with air cooled Morinis but type of oil can affect the smoothness
Sport and rear set linkages, loose or bad angles
Or with sports the front linkage on the spline pushed in too far.

Change of boots? Yours that is?

Mark
MickeyMoto
Posts: 2415
Joined: 22 Nov 2008 17:41
Location: Even further oop North

Re: Difficult 3rd to 4th gear change

Post by MickeyMoto »

Drain the oil and look for bits of metal. If it is broken I would not ride it. A gearbox lockup will not be pretty. Worth checking everything else first. May even be a bearing collapsing. Easy to change, but what damage has it caused to the rest of the gearbox? When I stripped my engine I changed all the roller bearings for new SKF ones. It cost £50 including the crankshaft one.

I think you need to ascertain what is wrong before you call Doug.
3potjohn
Posts: 1243
Joined: 02 Jun 2007 13:58
Location: Devon

Re: Difficult 3rd to 4th gear change

Post by 3potjohn »

A couple of handy Morini Gearbox videos on youtube. I recently had my motor apart and used a stout cardboard box with three holes to accommodate the left side of the crankcase and shafts as I do not have a decent engine frame. I also ran a little penetrating oil around the two dowels between the cases to help ease them apart but they were not too furred up.
As said the bearings are relatively cheap. I heartily recommend the use of jubilee clips or similar on the gearbox shafts to hold things in place as you remove them. I have experienced a problem going from first to second missing the change but in that instance my linkage was just touching the casing, this on a later 350. I also know that if you put second gear on backwards it last six years.
Photograph everything!
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