Parts to fix CB77 upshift 1st to 2nd gear?

[hefyjefy]

I am considering pulling the engine and trying to fix the upshift 1st to 2nd problem, which has gotten worse recently. Does anyone have information on which parts are likely to need replacement and whether they are available?
I am hoping that I can fix this without disassembling the whole motor I gather that its possible.
Geoff

[hefyjefy]

I am guessing this is the culprit can anyone confirm?

[tore]

I would suggest the bushing (no 17) - most likely:
https://images.cmsnl.com/img/partslists ... 8_c314.gif

Or maybe the forks (no 2):
https://images.cmsnl.com/img/partslists ... 9_f85e.gif

Apart from the drum suggested in the previous post.

[hefyjefy]

Yes I see, thank you!
Geoff

[sky.fred]

You need to be careful when buying drums and forks, because there are two models: one for classic boxes XXXXX - 268 - XXX and the other for rotary boxes XXXXX - 259 - XXX, which comes from the C72/C77.
Some sites may sell parts for rotary boxes without knowing it, as this is a little-known part that was reserved for the Japanese market, but can be found in old stocks.
viewtopic.php?f=22&t=7643370&start=56

[hefyjefy]

Once again thank you, this could get interesting...
Geoff

[Tim Allman]

This is a chronic problem with these engines. Item 14 in the image https://images.cmsnl.com/img/partslists ... 8_c314.gif has three variants, each with a different offset. If you have the original ones you will see that they are flat with a bit of machining. The others are offset by about 1mm and 2mm.

I fixed this problem by replacing the originals with the maximum offset ones (23943-259-305) on the mainshaft only. I suspect that they wear with use as the 1st to 2nd shifts are the most common and they are often 'hard'. It may also be that a small amount of wear on the mainshaft tapered bushing could also loosen things up. Since they are not very expensive I suggest buying both offsets but only two of each.

I doubt that the drum is a problem but you might look at the forks. If they are bent they can gently be straightened. If the pads are worn down I have heard that building them up with a welder and grinding them flat is possible but I have never seen it done.