Gearbox swap

[longandlow]

The gearbox on my sprint storm has started playing up, not selecting gear and jumping out of gear. The air shifter gives the box a hard time so it was only a matter of time. I am going to whip the motor out and change the gears, drum and forks. I have the tools covered, but what parts gaskets etc am I going to need? I don’t intend stripping the whole engine, just removing the lowers case.
Thanks in advance.

[freeridenick]

I can't see that being and easy job for you doing it like that. I assume you've looked at the service manual so your going to need some way to rest the engine on its heads and make it stable. Or use an engine stand that will rotate. Even so it's a heavy old lump.

Gaskets should just be the two engine covers if you don't take the heads off. Plus other parts like a new clutch lock nut.

[tony.mon]

I've always thought that you could pull off the lower case with the engine still in the frame if you simply turn the bike upside down.
If the cases don't separate easily you will have missed one of the crankcase bolts, there's a sneaky one above the clutch, so you need the clutch off first.
It's also going to need selector forks, I would have thought.

[longandlow]

Thanks guys.
I might try turning the bike upside down, but the engine bolts are all free so it might be just as easy to remove it. I intend to change everything in the gearbox as it's had a hard life. Just hope changing it and freshening up the clutch doesn't start the hope skip and jump issue, it launches great at the moment

[longandlow]

Well to update this post. I have now changed the complete gearbox, complete with selector forks and drum. I took the engine out in the end. What a pain that was, had to strip most of the bike down to do it. I turned the motor upside down leaving the heads etc on. Due to the chain guides being bolted to the lower case the tensioners had to be loosened, and timing reset after refitting. The gearbox swap was pretty straight forward, but again a lot had to be removed from the motor. Not a job for the novice, but it is doable with some mechanical ability and knowledge.
Found the 1st/2nd gear selector fork to be very badly worn.

[Kev L]

Well done on completing the job, here’s hoping all your hard work is rewarded when you test it

[tony.mon]

New parts, I hope.
It's not worth taking a chance on 2nd hand parts when it's that much if a faff to get it redone if the 2nd hand parts aren't good enough.

[longandlow]

I put a low millage gear cluster in, and new selector forks.

[tony.mon]

That should do it.
What times are you getting on the 1/4?

[longandlow]

Had to do a mod to the gear linkage to get the shifter to work. Ran 10.972 this weekend

[lloydie]

Well done .
I did a gearbox swap (ride in ride out in 7 hours once but I had just built the bike so everything came off easy .

[kemes]

The air shifter gives the box a hard time ...

May I ask what kind of parts have you used to build the air shifter?