Author Topic: Tech Tip: 2nd gear issue  (Read 15123 times)

Offline BlackAdder

2nd gear issue
« on: Saturday, 11 March 2017, 01:53 pm »
...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
« Last Edit: Saturday, 11 March 2017, 04:22 pm by gsxbarmy »
...I accidentally Mordored my motor, is it bad...?

Offline gsxbarmy

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Re: 2nd gear issue
« Reply #1 on: Saturday, 11 March 2017, 04:23 pm »
Top write up - thanks BA! (I've stickied this as well)
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Offline T 24

Re: 2nd gear issue
« Reply #2 on: Saturday, 11 March 2017, 04:37 pm »
Thank you BA! That was all I needed to know, unfortunately a little bit too late, I studied all that by my self and ended up the same result!
I had exactly the same problem with my second gear. And what did I do:
-Undercut 2 and 6 gears (5 degree)
-New shift forks
-New, billet made Hayabusa shift shafts
I havent tested it yet, but maybe next week, and I really hope that all this helps, and I can use power again.
« Last Edit: Saturday, 11 March 2017, 07:05 pm by T 24 »

Offline grog

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Re: 2nd gear issue
« Reply #3 on: Saturday, 11 March 2017, 06:43 pm »
excellent stuff. mine is k7, hope i never need your write up but never know. brilliant post

Offline T 24

Re: 2nd gear issue
« Reply #4 on: Sunday, 12 March 2017, 03:28 am »
Test run is done. Works great. No problem to find neutral position with undercut gears. A bit cold and slippery out there..

Offline BlackAdder

Re: 2nd gear issue
« Reply #5 on: Sunday, 12 March 2017, 04:41 am »
Nice to hear that it works. My gearbox was a bit stiff on returning the pedal after upshift for some 500km but now it works as well. And I dont have any problems finding neutral either.

...that looks pretty Finnish landscape btw... :D
...I accidentally Mordored my motor, is it bad...?

Offline Dan B

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Re: 2nd gear issue
« Reply #6 on: Friday, 22 December 2017, 11:09 am »
Hey guys.

I'm having some trouble getting from first to second gear on the 14: it's very clunky all of a sudden and sometimes gets stuck im nuetral especially under high load (i like to make the most of torque when racing sports bikes off the lights).

I've tried a few different shifting techniques to make the gear changes a bit smoother as i've been on lots of different types of bikes and there's always different tricks to getting the gear changes smooth, still does it a lot of the time.
Also get a bit of bouncing and a good clunk sometimes during gear changes if i'm shifting at a constant speed (with no load).

I'm wondering if this is related to this problem? Maybe early  (or late) signs.

The bike is my commuter and i spend a lot of time in traffic getting hot then cold and even though it has only 4,000km since the last service  (33,000km total) i've been told the oil might just need changing earlier and it might help a bit.

What do you guys think?
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Offline Andre

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Re: 2nd gear issue
« Reply #7 on: Friday, 22 December 2017, 04:30 pm »
Would first look if gearshift linkage is worn and check for clutch drag. Both can happen even at relative low mileage.

Changing engine oil would be good anyway, as well as clutch fluid.

Offline seth

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Re: 2nd gear issue
« Reply #8 on: Friday, 22 December 2017, 05:01 pm »
the problem on early gsx1400 gearboxes was they would jump out of 2nd gear into a neutral. due to problem alreay shown earlier in this thread.
if your having problems changing gear as andre said check/change your engine oil and check your clutch operation as the slave cylinder can become sticky/stiff to use if corroded

seth
only a slightly modified gsx1400
oh and a standard one too

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Offline gsxbarmy

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Re: 2nd gear issue
« Reply #9 on: Friday, 22 December 2017, 05:10 pm »
Also have the gearbox sprocket cover off and check fir any build up of chain grease around the clutch push rod behind the clutch slave cylinder.

Also do you still have the original clutch line fitted? If so, this could be on the way out and fitting a braided line would definitely help as the OEM lines “balloon” (so losing pressure) as they age as the rubber goes very soft.

Early K2/K3 and some K4 models known for second gear issues, typically on those which often use all the revs in lower gears - so given you said you frequently race sports bikes from a standing start, it’s possible that you have the early signs of 2nd gear failure, but do simple checks as above first and then let’s take it from there.
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Offline T 24

Re: 2nd gear issue
« Reply #10 on: Friday, 22 December 2017, 05:42 pm »
I think it is not our "2nd gear issue"
It can be your clutch, check it carefully.
Also changing oils/oil type can help.

Are you sure you dont have such a hurry that you dont close the throttle enough?

Offline KiwiCol

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Re: 2nd gear issue
« Reply #11 on: Friday, 22 December 2017, 05:50 pm »
Bung a quickshifter on it  :whistling:
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Offline grog

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Re: 2nd gear issue
« Reply #12 on: Friday, 22 December 2017, 07:32 pm »
or buy a gsxr 1000, sounds better suited to your needs.

Offline Dan B

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Re: 2nd gear issue
« Reply #13 on: Saturday, 23 December 2017, 06:19 am »
I'll do some of these checks today and see if it helps, cheers.

And grog: i'd love a gsxr1000 but i already own a worked r6 that i bring out on the weekends, the missus will only let me own so many toys.
The 14 is better on my back for the 30min each way commute to work, plus (ignoring my previous comment) it's just a great bike to ride in general, I don't wanna go backwards.
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Offline Kiwifruit

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Re: 2nd gear issue
« Reply #14 on: Saturday, 23 December 2017, 06:13 pm »
How fair is that Dan......has the missus only got two pairs of shoes ??

Ooops gotta go......"yes dear, won't be long" :worshippy:
Another great day on the right side of the grass.😎

 

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