Splitting 500cc crankcase

[Lyndoneil]

I want to inspect my Alpino gearbox,  according to the workshop manual I need to remove the cylinder head, pistons and barrels, which if its possible I would sooner not do, because of needing new gaskets,, new little end gudgin pin clips, possibly damage to the piston rings. etc
Is it possible to split the crankcase on one of these without removing the barrels etc?

 

[Thomas aus LAU]

Yes it works, even if this method is unusual.
I have already done this twice successfully in old 750 engines.

To make the work easier, you can hang the motor with the upper screws in an empty frame and turn it over. Alternatively, you can build a motor holder that holds the reversed motor.

Loosen the primary chain tensioner beforehand. You have to clean the sealing surfaces very well and you should use a good housing sealant (e.g. Loctite). As a precaution, I would replace the outer oil seals if they are not already new.

It made sense to change the spring of the selector drum mechanism if it is the original one.

You have to be careful, that the gear shaft locking pin doesn't fall out and that all half rings are in the right place to secure the bearings.

Please do not use force when uniting the housings. Even light blows with the rubber mallet are ok.
Before tightening the nuts crosswise, please check whether the selector shaft can turn = shift in all gears and whether the output pinion rotates accordingly.

Good luck.

Best Thomas aus LAU

 

[Paul Marx]

Er Thomas, there is no primary chain on a 500.

I haven't done muche to a 500 engine in donkeys years.
Take off all side casings of course.
Check parts lists or workshop manual to make sure that there's no hidden nuts on the top side, under the starter motor notably.

Turn engine over on the bench, take off all nuts and lift bottom case off.

Drain the oil first.
You don't need any sort of engine stand, do it on your work bench or on the floor.

Paul

 

[Thomas aus LAU]

Er Thomas, there is no primary chain on a 500.
Paul

Correct Paul, other things schould be ok ;-)

Took the english words from the 750 Laverdaparadies-page. So the mistake occurred.

Thomas aus LAU

 

[Dellortoman]

I split my Jota engine without taking the head and barrels off. But I did it the right way up rather than upside down. Lifted the top half of by putting the lifting sling under the ends of the crankshaft. The only time I turned the lump over was to get at the crankcase nuts on the underside.

The reason for doing it that way is that the gearbox remains unmolested in the bottom case, with all the shifting gear intact (shift drum, selector forks, etc.). It's a whole lot easier to strip and reassemble the gearbox in the bottom case rather than upside down in the top case. I presume the 500 has a similar gearbox design.