Undercutting gears?

[Biggles08]

I have a problem with my gearbox after my last race at manfeild. I was finding it difficult to engage 2nd to 3rd and 3rd to 4th. I have had the Gearbox stripped and it appears the dog gears that engage each other from 2-3 to 5th have rounded a bit at the edge. After talking to a few people in the know it seems this is a common problem with the 07 ZX6R.

My Questions:
1) who can I talk to who has had experience with undercutting gears that could talk to a machinist mate of mine before he attempts to do it (preferably with this model bike too)?

2) once they have been rounded on the edges, can they be saved by undercutting them or do you NEED to start with new gears?

I have a few ideas of how to fix this but wanted a bit of feedback from you lot :-)

Cheers
Biggles08

[Motu]

Keystone gears were a rough bodge up that is now factory issue.

[speedpro]

I have a friend who has done a few plus made his own gears. Is it really a problem with the gears crapping out on those or is it just yours? Undercutting is good but it does have it's drawbacks as well. It wasn't caused by how you use the box?

[SixPackBack]

How does your machinist mate intend to under cut the gears? being hardened he will be limited to either grinding, spark eroding or wire eroding. Any other method of maching is likely to end in tears....your tears Biggles!

Who can you talk to?.....try Precision engineering in albany, they may not have been involved in undercutting but I know they have a gear hob and get involved with performance gears etc, if they cannot help they will know who can.

HDTboy will also provide guidance having been involved with two smokers ZX6

[t3mp0r4ry nzr]

message Jay Lawerance (jay racer or sumthing) on here about it. He MAY have done it to the zx6r. He did do it to the r6.
spark eroding rings a bell. best get the info from the source though aye.

[Biggles08]

How does your machinist mate intend to under cut the gears? being hardened he will be limited to either grinding, spark eroding or wire eroding. Any other method of maching is likely to end in tears....your tears Biggles!

Who can you talk to?.....try Precision engineering in albany, they may not have been involved in undercutting but I know they have a gear hob and get involved with performance gears etc, if they cannot help they will know who can.

HDTboy will also provide guidance having been involved with two smokers ZX6

I have talked to Jay L about it and he has done a couple (or rather had done) of gearboxes. One was done by an air grinder and only a touch was taken off... I know they are hardened and need to be done the right way. I've talked to a few people about it and it seems a fairly cloudy subject actually.

I'm going to buy new dog gears anyway but I would like to have a crack at undercutting the old ones to see if its any better. Apparently it is a commone fault with ZX6R's....as far as my shifting goes I'm giving the gearbox death...but hey, thats racing!

[Biggles08]

I have a friend who has done a few plus made his own gears. Is it really a problem with the gears crapping out on those or is it just yours? Undercutting is good but it does have it's drawbacks as well. It wasn't caused by how you use the box?

As per my reply to sixpackback...yes it is because I'm hammering them but I don't see that changing so I need to try something else...I've heard undercutting gets rid of a lot of the problems.

[SixPackBack]

I have talked to Jay L about it and he has done a couple (or rather had done) of gearboxes. One was done by an air grinder and only a touch was taken off... I know they are hardened and need to be done the right way. I've talked to a few people about it and it seems a fairly cloudy subject actually.

I'm going to buy new dog gears anyway but I would like to have a crack at undercutting the old ones to see if its any better. Apparently it is a commone fault with ZX6R's....as far as my shifting goes I'm giving the gearbox death...but hey, thats racing!

An air grinder?......what a fooken animal.
Nothing cloudy Biggles, you need only establish three parameters:

• The amount of material removal.
• The profile of material removal.
• Method of material removal.

Do some homework bro.

[Laava]

I had Tjebbe Bruin do 2nd gear for me on me ol' 450 Honda. Is he Precision Eng?

[Deano]

message Jay Lawerance (jay racer or sumthing) on here about it. He MAY have done it to the zx6r. He did do it to the r6.
spark eroding rings a bell. best get the info from the source though aye.

Ditto..................

[SARGE]

How does your machinist mate intend to under cut the gears? being hardened he will be limited to either grinding, spark eroding or wire eroding. Any other method of maching is likely to end in tears....your tears Biggles!

AH Gears in Penrose behind the stadium can do it

[F5 Dave]

An air grinder?......what a fooken animal.. .

I think you'll find that was far away from home base trying to make an ill-conceived roadbike gearbox cope with racing the next day after untold problems. Needs must.

[Ixion]

Keystone gears were a rough bodge up that is now factory issue.

Meh. Keystone gears are for Keystone Kops. Just weld the gear wheel to the shaft. Problem sorted once and for all.

[TripleZee Dyno]

I have a problem with my gearbox after my last race at manfeild. I was finding it difficult to engage 2nd to 3rd and 3rd to 4th. I have had the Gearbox stripped and it appears the dog gears that engage each other from 2-3 to 5th have rounded a bit at the edge. After talking to a few people in the know it seems this is a common problem with the 07 ZX6R.

My Questions:
1) who can I talk to who has had experience with undercutting gears that could talk to a machinist mate of mine before he attempts to do it (preferably with this model bike too)?

2) once they have been rounded on the edges, can they be saved by undercutting them or do you NEED to start with new gears?

I have a few ideas of how to fix this but wanted a bit of feedback from you lot :-)

Cheers
Biggles08

My only experience with undercut gears is fitting them.
But generally speaking undercutting is done so that the gears lock into engagement when under load. ie if the trans pops out of gear when you give it a handful, or when you shut the throttle. It can also help with engagement because the undercut "pulls" the dogs into engagement when under load.
Too much undercut and it can make shifting difficult for the same reasons.
I havent seen a ZX6R box but I have repaired a few transmissions over the years and I havent come across a gearbox yet that couldnt be improved or made less worse, with careful assy ie shimming, checking engagments (blueprinting for want of a better word) etc.
Check the stock gearbox and you may find it is already undercut.
If you are having trouble getting into the next gear worn dogs dont help especially if you are powershifting or not using the clutch or generally thrashing it. Basically the dogs end up sliding over each other instead of engaging if the power comes on too quickly. Factorypro shift kit can help here. They work by rotating the shift drum a bit quicker than stock and get the gearchange done quicker.
Whatever you do, you need to start with new dogs.
If its a common problem whats the common solution? or do people just keep chucking parts at it?
Good luck

[R1madness]

I have a problem with my gearbox after my last race at manfeild. I was finding it difficult to engage 2nd to 3rd and 3rd to 4th. I have had the Gearbox stripped and it appears the dog gears that engage each other from 2-3 to 5th have rounded a bit at the edge. After talking to a few people in the know it seems this is a common problem with the 07 ZX6R.


Cheers
Biggles08

Did you read the "clutchless gear changes" thread? This is a common problem with every bike thaat has clutchless gear changes on a regular basis.... not just ZX6s.