Montesa 348 gear selection

[Joseph]

Hello,

New to the site and my fairly recently acquired 1976 Montesa cota 348 MRR.

I am having problems selecting the gears. With the bike running and moving, going through the gearbox sequence from 1st to 6th gear is quite difficult with a very stiff selector lever, gears not engaging correctly and quite a few neutrals in between. Changing back down from 6th to 1st is better but probably because it is easier to apply downwards pressure on the lever.

All the gears are there, it is just difficult getting them. I have tried adjusting the concentric nut on the selector mechanism until I have got the best lever movement possible but it is still problematic. The circular slotted ratchet mechanism also works cleanly and is the correct way round.

I am thinking the problem lies in the gearbox itself but just wanted to check if there was anything else I could check before I open the case up and all that entails.

All advice much appreciated in advance. Joe.

 

[b40rt]

https://www.trialscentral.com/forums/topic/30515-cota-348-h…

have you looked through these ?

[barnesy]

Hi Joe,

I've just finished rebuilding my 348 and there's a couple of things I'd try before splitting the engine.

Put in new selector pawls and a shift return spring as they are inexpensive and your current pawls are probably chipped.

Take out the detent plunger on the right side of the engine and check the detent spring is free and not gummed up.

I'd also take the selector mechanism off and try the gearbox selection with a mole wrench on the selector drum to see what

the gearbox is like, then you can isolate whether its the selector mechanism or not

I'd also put in fresh gearbox and clutch oil, morris golden film works well in the clutch, you need old style oils not synthetic stuff.

Hope that helps

Cheers

Guy

 

[Joseph]

Thanks for your reply's fella's,

Good advice, thanks, I will check those things out as soon as I get time and report back. Joe

[Joseph]

Hello Guy, 

This evening I checked the detent plunger on the right hand side of the engine, this was fine and working well.

Next took off the clutch case and removed the selector ratchet mechanism and plates etc all which seems ok but with a little age related slack mostly caused by some wear in the selector lever shaft bush in the clutch outer case.

I took your advice and connected some mole grips onto the selector drum shaft splines and went up and down the gears while gently rocking the clutch or rear wheel: the shaft was quite stiff and difficult to move to select the lower gears 1st, 2nd and 3rd, whereas 4th 5th and 6th were definitely easier with shifting back down the range being more precise.

Interesting to note that the difficulties in movement with the selector mechanism removed were as replicated when they were connected and worked through the shift lever.

This has more or less confirmed my suspicion that the problem is within the gearbox somewhere but unfortunately it is not a place I am familiar with.

Where to go from here? The bike is great and having apparently not being started or ridden for years it now starts, runs and pulls really well but I am a bit reluctant to open the gearbox up. But I like things to be right and ultimately it may be the only way to see what is causing the problem and get the bike right again.

Thanks for your advice anyway, it's much appreciated. Joe

[barnesy]

Hi Joe,

It looks like you've done all you can without splitting the cases, if you decide to go ahead and split the cases I'd say its a finiky rather than hard job take lots of photos and make a note of what order the shims in the gearbox are. With my bike it ran well but was noisy compared to other 348's I'd seen at trials it turned out to be the rod/big end bearings that were worn. I replaced the gearbox bearings and main bearings while it was apart these are relatively cheap and available from inmotion (other supplier are available..).

I'd never split an engine before so was a bit daunted when I started but the bikes runs great now so I'm glad I persevered with it, there's lots of info on these forums and feel free to reach out if you need any info/tips.

Cheers

Guy

 

 

 

[Joseph]

Thanks Guy, 

You have given me some inspirarion to get the job sorted as while at the moment the engine on the bike is good, the gearbox lets it down making it a bit difficult to ride.  

I will give it a go in due course, thanks again.

Cheers, Joe

[NFC]

On 4/5/2021 at 11:56 AM, barnesy said:

Hi Joe,

It looks like you've done all you can without splitting the cases, if you decide to go ahead and split the cases I'd say its a finiky rather than hard job take lots of photos and make a note of what order the shims in the gearbox are. With my bike it ran well but was noisy compared to other 348's I'd seen at trials it turned out to be the rod/big end bearings that were worn. I replaced the gearbox bearings and main bearings while it was apart these are relatively cheap and available from inmotion (other supplier are available..).

I'd never split an engine before so was a bit daunted when I started but the bikes runs great now so I'm glad I persevered with it, there's lots of info on these forums and feel free to reach out if you need any info/tips.

Cheers

Guy

 

 

 

Hi Barnesy,

I have a problem with my kick start shaft on my 348.

 

Yesterday went to start the bike and when I kick it it moves forward. I’m sure it was in Neutral. Than I’ve kick it again and it turned free and moved to the out side.

This problem never happened to me on other cotas.
Do I need to split the cases??

 I will appreciate any help as I live in a country that classic cotas are very rare.

Thank you 🙏 

[barnesy]

Hi NFC,

Unfortunately I think you will have to split the cases as the kickstart shaft is held in place by a circlip on the other side of 

the case and this looks to have dislodged. The kickstart shaft locates in a bronze bush in the other case and this can wear (as mine had) which may have contributed to the shaft dislodging.

Sorry to be the bearer of bad news...