second gear stuffed

[Camel]

I've undercut a few Busa 2nd, 3rd gears. Recently did a set for a K6 engine from an off-road buggy. These things hammer hard, particularly on the gears.



They also bend the shift forks...


...usually because the shift fork shafts flex so easily. I've pulled apart a box where the shaft was still flexed by partially dislocation of the shift fork pin. gently levered it to one side and it popped back in - pulled it apart, checked the shaft and it was straight!

Here's the standard shaft, look how thin they are!



Here's the tool steel shafts:



I usually replace the shift fork shafts with tool steel jobbies because they don't flex. I also check the cases because with the shafts flexing they tend to oval out their support boss holes in the cases.



A few months back I had to undercut a guys 3/4 gear dogs between heats ( an all saturday night special). The dogs were pretty bad (another buggy) and I had to take heaps of meat off. So much so that I advised him not to use it and skip the following days event. He was keen so I put it in and he had no problems. I've been trying to get him to replace the gear but he's still racing with it! I've got a photo of it somewhere, too embarrassed to post it!

Camel

[Legend]

I dont agree that you need HD shift shafts.

The shift forks do the gear shifts but are not designed to hold the gear/dogs in place while under load, when the fork is put in the positon of holding the bike in gear that is when the wear starts.

If the gears are undercut properly then they will hold themselves in place and in gear.

No matter how strong you make the shafts the week link will always be the forks.

Modifing the shift drum also helps.

Just my opinion.

Leonard.