Undercut tranny

bnf96fireblade · 11-06-2009, 2:15 AM

Hey,
I am in the throws of replacing the tranny in my 96 900rr. In preparation for this I purchased a "97" 900rr tranny off of ebay for a couple hundred bucks. I sent the newer tranny in to have it undercut so I don't have the same problem with 2nd gear popping out again.

So I get the undercut tranny back and start tearing into the bike. I finally get the motor out today and split the cases... are you kidding me!? The tranny I just spent 300 bucks to have undercut is apparently not from a 1997 CBR 900rr. I compared it to the one in the manual, and it seemed right. Now that I have my tranny out to compare I can see that it is similar, but not the same! I have no idea what bike this tranny came from. The shafts are the same diameter, but not the same length. I may try to transfer all the goodies onto the shafts from my bike and see if it all meshes. Will this work, I don't know... any ideas?

bladeracer · 11-06-2009, 2:32 AM

Quote:

Originally Posted by bnf96fireblade

Hey,
I am in the throws of replacing the tranny in my 96 900rr. In preparation for this I purchased a "97" 900rr tranny off of ebay for a couple hundred bucks. I sent the newer tranny in to have it undercut so I don't have the same problem with 2nd gear popping out again.

So I get the undercut tranny back and start tearing into the bike. I finally get the motor out today and split the cases... are you kidding me!? The tranny I just spent 300 bucks to have undercut is apparently not from a 1997 CBR 900rr. I compared it to the one in the manual, and it seemed right. Now that I have my tranny out to compare I can see that it is similar, but not the same! I have no idea what bike this tranny came from. The shafts are the same diameter, but not the same length. I may try to transfer all the goodies onto the shafts from my bike and see if it all meshes. Will this work, I don't know... any ideas?

Can you show us the differences with pictures perhaps?
Do the shafts drop in at all or are the bearings not in the same positions?
Did the place that undercut it have any idea what it's out of?
Was the seller selling other parts that could identify what the bike was?

bnf96fireblade · 11-06-2009, 2:07 PM

I can shoot some pics.
The mainshaft is shorter than the original, but the bearings are all the same size. The gears have different amounts of teeth on them, so I've been looking at parts fisches to see if I can find what it is. It is definitely a honda, and maybe even a cbr at that.
The place that undercut it is back east, and I'm out west.
Unfortunatley I bought it back in Aug, but haven't torn the bike down 'til now since the weather is getting bad. I tried contacting the guy through ebay, but he doesn't currently have anything for sale, so I don't know how active he'll be.

bnf96fireblade · 11-06-2009, 4:31 PM

I think I may have found what it is. The parts fiche on bikebandit may have a typo, and if so it looks like it is from a 2003 CBR 600rr. I will still upload photos 'n' stuff for everyone as I may have a nice undercut tranny from a 2003 600rr for sale.

BurtonF166 · 11-06-2009, 4:33 PM

....what does that mean, an undercut tranny?

Teach me!!

bladeracer · 11-06-2009, 4:35 PM

Quote:

Originally Posted by BurtonF166

....what does that mean, an undercut tranny?

Teach me!!

It means the dogs are cut back so that under load they pull the gear cluster together.
APE - Transmissions

BurtonF166 · 11-06-2009, 4:37 PM

New bikes are coming with undercut gears, thats useful. Why not earlier?

Were bikes not powerful enough to cause it to slip?

bladeracer · 11-06-2009, 4:40 PM

Quote:

Originally Posted by BurtonF166

New bikes are coming with undercut gears, thats useful. Why not earlier?

Were bikes not powerful enough to cause it to slip?

Just cost I'd guess.
Unless you're working it hard or you're hopeless at shifting then it's not necessary.
Nowadays it's probably considerably easier and cheaper to undercut the dogs from the factory than it used to be.

BurtonF166 · 11-06-2009, 4:41 PM

Are they aluminum?

bladeracer · 11-06-2009, 4:47 PM

Quote:

Originally Posted by BurtonF166

Are they aluminum?

No, steel. Probably 4140 at a guess.

BurtonF166 · 11-06-2009, 6:47 PM

Wow, healthy carbon content. Sure is a pain to machine steel.

bnf96fireblade · 11-06-2009, 8:39 PM

Hey, I'm back! Yes they were undercut by RC's Performance, sorry Larry, and they are in fact from a 2003 CBR600rr. I counted all the teeth on all the gears, and they all match up with the 03 600rr. Photos are still coming.

Larry, can I swap all the gears onto the main and countershaft on my bike? I hate to have wasted the money undercutting gears I cannot use.
Thanks

bnf96fireblade · 11-06-2009, 9:03 PM

Here are the photos. The one on top is from what looks like a 2003 600rr and the one on the bottom is from my bike, a 96 900rr. These are the mainshafts. The large bearings are different and 6th gear (2nd one in from the right) is wider on mine. Other than that, quite similar. Oh yeah, my shaft is longer.

bladeracer · 11-07-2009, 2:43 AM

Wow! I can see how you made the mistake, they look the very similar.
There's only one way to know if you can use it and that's to try it and see.
It doesn't look possible to me though.

bnf96fireblade · 11-07-2009, 10:33 AM

I'm going to try swapping the cut gears to my shafts tomorrow and see what happens.

bnf96fireblade · 11-10-2009, 1:08 AM

They won't fit, so it is going up for sale!