SF1 won't select 5th

Great that you've now eliminated the external selector assembly. If you can get boroscope pics of the straight edge of the shift plate/drum (rather than the side-on pic you show) and can see the area directly under the plate edge (where it comes closes to the bottom of the crankcase) it will hopefully show what's blocking that last 10 degrees of rotation.

If worse comes to worse, splitting the cases is not a huge task - and if there are signs of damage from a DPO using a hammer, it may well be worth investigating. With care, you can even leave the entire top end (head and barrels) intact) and just remove the lower case. But the boroscope is your friend before going there.
 
I investigated further with the boroscope and I can get a view looking along the lower edge of the selector drum. It is difficult to get a good picture but there is no obstruction as far as I can see. This is a direct image through the camera so is reversed. There is also a small mirror attachment which allows a side on view which is the right way up. I scanned along the lower edge of the selector with this and there is no visible obstruction. The images are even worse quality due to the mirror and the lens getting dirty.

It seems like I will have to split the engine and have a look inside. I will keep you updated on my progress.

IMG_1127.JPG
 
Just thinking, could it be that shaft on which the forks are fixed is not secured by the small bolt which must be inserted in the 2nd gearshaft bearing left side? If so, and the shaft moves out ( under the coupler) it can be secured from outside by a screw an a washer without opening the engine totally.
 
I bit the bullet and split the engine. With the help of Ian another Lavada enthusiast and close neighbor we dropped the engine from the frame, turned it upside down and removed the lower crankcase. The selector mechanism remained in the lower half. The reason for the non selection of 5th was that the 5th gear selector fork was seized into the shaft or I should say rusted onto the shaft ( you can see a trace of rust on the shaft). There was a lot of rust inside the engine. I don't know why except the engine had only been briefly started once between 1990 and 2022. I assume condensation had caused rusting. Maybe these Italian bikes are not designed for the extreme Scottish weather :). So a lot of penetrating oil, a bit of heat and some careful bashing and I unstuck the fork. You can see on the shaft where it was rusted on.

Has anyone else had such a problem?

1656095072725.jpeg

1656095747440.jpeg
 
That's a good reason for pulling an engine that hasn't run in years to bits.
You may well have rust spots on the main bearing cages or the big end rollers and crankpins.
Bang

Nothing to do with Italian engines or Scottish weather.

Paul
 
one issue is the humidty but also the different alloys will have some galvanic reactions which will produce something like rust also within a bearing or two different materials. -electro chemic series of metals
 
Wow, I didn't expect that to be the reason, but clearly the engine needed to be split - definitely worth looking into it deeper to ensure you have a motor ready for a new long life.
 
If the gearbox is that rusty, which is quite unusual, the cylinders and piston rings will surely show a lot of rust pitting. Ball and roller bearings (cams, big-ends, crank mains, gearbox) will also be affected.

Absolutely no use in continuing without a total strip and overhaul. Even if the engine uses little to no oil presently, this will change quite dramatically within the next couple of hundred kms. Quite possible that an accompanying rumble will develop as well. :rolleyes:

piet
 
strongly agrtee with Piet, strip the whole thing including the top end, check everything and everywhere, its also a lot easier to start re-assembly of the gearbox into an empty lower half case, a good time to clean up the internal and external finishing as well, through carefull checking,measuring and cleaning, it is very often possible to NOT to have to spend huge amounts of cash, many items may well be within service limits given the mileage, if you see rust or pitting from rust in any bearing, then it is scrap, if the bores do not show any kind of ridge then you are laughing, but even if they do maybe a hone and new rings (always a must) would work, rings and valve springs after a valve relap, is automatic (for me) as are new gaskets and seals. It can be a problem getting a new cam chain to fit on a Breganze 750 twin, spacers to make up the thickness of the engine top cover can help, so that pretorquiung can take place, but it can still be problematical, does anyone know why? (twins only)
CLEM
 
Cosi said:
Quite fucked is the diagnosis?….
Click to expand...
Quite, with a capital "F".

Here's what can be expected to be found in the crank... can't remember if this particular rod was scrapped or if it was salvaged with further honing. Because the Breganze factory, in its infinite wisdom, fitted slightly under-sized big end rollers, damage such as this can be cleaned up to suit larger rollers, especially when over-size crank pins are to be used.

Granted, this was a very rusted example, but, there's generally not much difference inside the bearings between lightly or heavily rusted.

pietLH rod.JPGPICT2341.JPG
 
CLEMTOG said:
strongly agrtee with Piet, strip the whole thing including the top end, check everything and everywhere, its also a lot easier to start re-assembly of the gearbox into an empty lower half case, a good time to clean up the internal and external finishing as well, through carefull checking,measuring and cleaning, it is very often possible to NOT to have to spend huge amounts of cash, many items may well be within service limits given the mileage, if you see rust or pitting from rust in any bearing, then it is scrap, if the bores do not show any kind of ridge then you are laughing, but even if they do maybe a hone and new rings (always a must) would work, rings and valve springs after a valve relap, is automatic (for me) as are new gaskets and seals. It can be a problem getting a new cam chain to fit on a Breganze 750 twin, spacers to make up the thickness of the engine top cover can help, so that pretorquiung can take place, but it can still be problematical, does anyone know why? (twins only)
CLEM
Click to expand...
I quite agree with me as well Clem.

Paul
 
Well, thanks for all the advice and portents of doom. I have cleaned up the spindle and selector forks and reassembled the gear clusters in the lower crankcases. The gears now select perfectly, which is good.

I haven't decided how to proceed apart from cleaning what I can and replacing seals and any of the gearbox bearings which seem worn. My main concern would be the big ends but they presumably have a good supply of high pressure oil so hopefully will be OK.
I will keep you all informed.

Thanks again. Colin
 
ColinJ said:
Well, thanks for all the advice and portents of doom. I have cleaned up the spindle and selector forks and reassembled the gear clusters in the lower crankcases. The gears now select perfectly, which is good.

I haven't decided how to proceed apart from cleaning what I can and replacing seals and any of the gearbox bearings which seem worn. My main concern would be the big ends but they presumably have a good supply of high pressure oil so hopefully will be OK.
I will keep you all informed.

Thanks again. Colin
Click to expand...
If the big ends and main bearings, along with crank pins are pitted, you can throw oil or ketchup at them. They don't have a supply of high pressure oil, it's a no pressure all bearing engine.
Nothing to do with portending doom, just healthy mechanical practice.

Paul
 
Hi Guys, it is me again with my rusty engine. I am not sure what to do about the rest of the engine but I have started by replacing the gearbox bearings and I have another problem. I can't get the 5th gear bearing off the main shaft. There is no room for a puller to get a grip. I am contemplating trying to weld a ring onto the outside of the bearing and then use a puller. I might try heating it up a bit.

Any thoughts on how to remove the bearing?

Thanks Colin
 
yes, you need a knife edged split bearing puller, cheap as kits to buy at shows, does various sizes, not much cop but its a job that doesnt get done very often by home mechancs, so works out well, sometimes called a bearing splitter.
EG Ebay item number 393420043154. (I didnt check the spec of the splitter or bearing to see if this kit works on your gearbox stuff, it was to give you an idea of what is needed)
a little worrying that you needed to to ask that question. Never attempt a rebuild of this nature if you dont posses the right tools or havent borrowed them from ILOC.
CLEM
 
CLEMTOG said:
yes, you need a knife edged split bearing puller, cheap as kits to buy at shows, does various sizes, not much cop but its a job that doesnt get done very often by home mechancs, so works out well, sometimes called a bearing splitter.
EG Ebay item number 393420043154. (I didnt check the spec of the splitter or bearing to see if this kit works on your gearbox stuff, it was to give you an idea of what is needed)
a little worrying that you needed to to ask that question. Never attempt a rebuild of this nature if you dont posses the right tools or havent borrowed them from ILOC.
CLEM
Click to expand...
CLEM, Thanks for putting me on the right track. I worry all the time about my mechanical abilities especially since the SF1 went from a working bike that sounded great but wouldn't select 5th gear to pile of bits with dubious bearings throughout. Anyway I shall plod on with your help.

Thanks again Colin
 
You must log in or register to reply here.
Back
Top