Hi,

Currently undertaking an engine and gearbox rebuild over the winter months on my 650cc 126 engine and box. I can't for the life of me undo to nuts on the end of the input and output drive. I have tried locking the gears as suggested in the manual and the shafts put up quite a bit of resistance when I try and undo the nuts, but then the shaft eventually turns. It's incredibly frustrating and I am completely stuck as to what to do. Any ideas?

Sometimes a short sharp force will loosen the nuts especially if you have the swaged type locking nuts. So you could try locking the gears then get either a ring spanner or socket and T-bar on the nut then give it a quick clout with a mallet in the right direction. It has worked for me when sometimes applying all the force you can muster has failed.

....and maybe a careful application of blowtorch heat for a minute or so, just in case someone has Loctited it?

Thanks guys. Finally managed to do it then hit another snag which I eventually managed to overcome. Gearbox now fully stripped and refurb kit purchased.

Can anyone advise on whether to replace the bearings or not? Visual inspection doesn't show any obvious wear and they appear to rotate smoothly enough. First and reverse gears are badly worn suggesting that the box has done a fair few miles so I was going to change them as a matter of course. However, in my Haynes manual it says if you replace the bearing at the selector end of the output shaft it will upset the the position of the pinion in relation to the crown wheel? Surely replacing like for like, albeit new for worn shouldn't matter?

Jamie

There are two sets available
Polish and Italian
I bought Polish and they weren't suitable for a frigging lawnmower
You get what you pay for

worth knowing thanks Andrew. Having examined my existing ones they appear to be Polish. I assume that if I replace them with Italian I won't have any snags. Did you replace the bearing at the selector end of the output shaft? If so did you make any adjustments with regards to it upsetting the the position of the pinion in relation to the crown wheel as it states in the Haynes manual?

Jamie