...the problem that led me to this community in the first place...
I did write about it back at 2012 but... ...I managed to save it, so here you go:
Some of us has experienced the second gear issue, some of us has heard about it and some wonder if they have it too. I thought to briefly show whats broken from the gear box when it happens.
Im building my bikes gearbox for the second (and hopefully last) time now so I think that I know somehow the symptoms and the annoyment of the problem. In my bike (k7 model that is) it first felt like the engine would be cutting off at the peak torque range every now and then - the engine
felt like it would be cutting off and on (that is how I FELT it) and after it became worse it was quite clear that the gears were fckt. That was the first time.
The second time I knew right away what was the issue but sense the driving season was just starting I just kept riding, usually just skipping the 2nd gear and changing straight to 3rd when accelerating. Have I'd been a bit more gentle with the trhottle, I would'nt had to change also the 3rd gears driven erm, spocket.
So, 2nd and 6th gear are both engaged when you have 2nd gear on. All the power comes "thorough" 6th gears sprockets where the second gears sprockets attach (the two most left sprockets, 2nd gear engaged):
There's the 2nd and 6th driven gears, on the axle where the front sprocket attaches. The smaller sprocket "locks" to the small windows in the larger spocket. On the earlyer 1400's these where made form a bit different material and so some of them had the gearbox problem more often. In the later models it was fixed but still some got broken, along with mine. Two times.
Anyhow, whilst accelerating, especially when shifting without clutch, these parts wear and when they start to be round the 2nd gear dont lock as well anymore and starts to bounce. And now we have a problem that just gets worse every time it happens.
After the gears bounces for the first time it does some damage to the gear shifting forks (they move the gears in right positions when changing gears). The gearshifter fork bends a bit and starts to wear too. After a while it looks like this:
And one doesent have to be a rocket scientist to figure out that this makes the problem even worse. Added to this there's allso the axle where the gear shifter forks moves - it might bend as well and that leads to a situation where the second gear doesent keep engaged at all. This happens actually quite fast from the first "whattahellwasthat" moment.
Cure
Undercutting the gears.
In most cases there are no other damages to the engine exept the 2/6 gears, gearshifter forks and the tubes (referring the axels as tubes as they are not solid) where the gearshifter forks slides around. You can also use the old sprockets after they have been machined, undercutted as those in the picture above. The idea is to machine the slots in small angles so that when the gear is engaged it will hold better. Suzuki did it the first time with -92 GSXR 1100 to keep the gearbox from pulling a part. In 1400 other gears are undercutted (looks a bit like a fishtail, look at the pic below, uncut sprocket at the right)
but the 2nd gear is left alone to help in finding neutral. When you have undercutted gears (especially if you have similar than the sprocket above, it has up- and downcut, or a full "race cut", to hold the gears allso during engine brake - not that usefull or necessary on a road bike...) you might have to change to 1st gear first and then up to get neutral.
The other thing is to change the gearshifterforktubes to heavyer ones that dont bend that easily:
OEM tube at the left, APE raceparts axels (1st Gen Busa performance parts for drag strip) at the center and right, you can see the difference. They wont bend so it shoud make a difference in gear shifting and the lifespan of the shifterforks.
Interesting part is that most of 1st gen hayabusas gearparts will fit to GSX. If one wants to change gear ratios for example, you could take a look what there is for hayabusa. The whole race gearbox is a bit expensive though, but its there.
While doing your fixing, order a set of new bolts for the cases and use the torque wrench. Them bolts doesnt take loosening and tightening that well, at least multiple times. It's way cheaper and faster than having a bolt snapping in the engine halves:
...and check that the geaxbox axle bearings are in the right position (the holes line up with the retainer studs) to avoid further delays...
Good news is that you can fix all of that.
The parts needed as follows
(2nd driven gear 93,44€ if you cant get the original undercutted)
2432124F00000
(6th driven gear 109,19€ same thing with this one)
2436124F20000
Gear shifter forks 82,52€ / piece, two needed
2521124F10000
The third gear shifter fork 83,37€ one needed
2523124F20000
And if you want to go all-in:
Billet shift shafts:
Billet Shift Shaft Kit Suzuki Hayabusa 1999-2016 (APE Raceparts TSSH1300 or Brock's Performance)
Heavy duty driven axle:
Hayabusa Billet H/Duty Output Shaft (nova 002 or Robinson industries)
and your transmission should be bomb proof after those.
Hope this helps somebody.
Cheers,
BA
