02 YZF R1 Transmission (2nd) | GTAMotorcycle.com

02 YZF R1 Transmission (2nd)

R

Rider94

Member
Hi everyone,

My 2nd gear is starting to get the ol’ Yamaha slip. I know that it is from the dogs being worn down over time and also that this is a very common issue with this particular bike. JW if anyone has gone through this experience and how much time I may have before needing to gut the tranny open and replace 2/6 gears & potentially the fork. I can take (2nd gear) twists in 1st and 3rd and not kill the throttle in 2nd as well to be safe and to try and slow down the process. I also know that there are many variables that can effect the rate of this issue. Just looking for anyone’s stories who can relate... cheers.

65,000 km on her btw
 
I've had second gear spin loose on it's shaft on a Suzuki TS185 (it's only press fit on the shaft), I've had a bent shifter fork on a Montesa 360VA, but only the Suzuki exhibited the symptoms you describe of actually slipping while still in gear and still shifting without problems, are there any photos anywhere showing an example of the damage that happens when this happens to an R1?
 
It's not a matter of a press-fit part slipping on a shaft. It's that the sharp edges of the engagement dogs (and the slots in the adjacent gear that the engagement dogs go into) have been worn rounded in combination with the shift fork being slightly bent so that the gear is no longer being pushed far enough into the adjacent gear to hold it engaged. The forces of the rounded engagement dogs try to force the gear out of engagement when drive torque is applied.

Usually what happens is that the initial bit of rounding happens over a very long time through normal wear, then at some point someone misses a shift leading to grinding and much faster wear, then it very quickly gets worse and worse. Once it starts "slipping" (i.e. grinding), those engagement dogs are not long for this world.

You can ride the bike pretty much as long as you want by skipping second gear (do a double upshift from 1st).

On a 17 year old high-ish mileage bike that isn't really a collector's piece (and which doesn't have a cartridge gearbox!) the significant labour involved to fix this opens the question of whether to pay to fix it or to part out the bike and get something else. Are the parts available from Yamaha?
 
If that's what is happening on him there must be a lot of metal shavings floating around in the oil.
 
Yup. And in the oil filter, and sitting on the bottom of the pan, and in the oil pump inlet screen.

I use magnetic drain plugs to minimize the amount of this stuff that the oil pump has to deal with.
 
Trials said:
If that's what is happening on him there must be a lot of metal shavings floating around in the oil.
Click to expand...
IIRC to solve the problem, people would undercut the dogs on second gear so they would naturally be pulled together (slight ramps). I'm not sure if you could just buy them this way or if every time a fresh set of dogs were machined. The downside is shifting out of second with much load on the transmission isn't going to happen.
 
Serious tear-down even to check it unless you attempt a borescope inspection.
 
Brian P said:
Yup. And in the oil filter, and sitting on the bottom of the pan, and in the oil pump inlet screen.

I use magnetic drain plugs to minimize the amount of this stuff that the oil pump has to deal with.
Click to expand...
that is ******* brilliant lol.
Can you just get them anywhere?
 
Brian P said:
It's not a matter of a press-fit part slipping on a shaft. It's that the sharp edges of the engagement dogs (and the slots in the adjacent gear that the engagement dogs go into) have been worn rounded in combination with the shift fork being slightly bent so that the gear is no longer being pushed far enough into the adjacent gear to hold it engaged. The forces of the rounded engagement dogs try to force the gear out of engagement when drive torque is applied.

Usually what happens is that the initial bit of rounding happens over a very long time through normal wear, then at some point someone misses a shift leading to grinding and much faster wear, then it very quickly gets worse and worse. Once it starts "slipping" (i.e. grinding), those engagement dogs are not long for this world.

You can ride the bike pretty much as long as you want by skipping second gear (do a double upshift from 1st).

On a 17 year old high-ish mileage bike that isn't really a collector's piece (and which doesn't have a cartridge gearbox!) the significant labour involved to fix this opens the question of whether to pay to fix it or to part out the bike and get something else. Are the parts available from Yamaha?
Click to expand...

I’m not sure if the parts are available from Yamaha. Haven’t looked into it that far yet. I imagine they would be since this is such a common theme with these bikes, I believe they added more teeth on the gears in later models. Also if I were to do it myself I don’t think it would cost me too much $. Just a lot of time and headaches.

Thanks for the response.


Sent from my iPhone using GTAMotorcycle.com mobile app
 
bigpoppa said:
that is ******* brilliant lol.
Can you just get them anywhere?
Click to expand...
Some bikes already have magnets on the drain plugs, super easy to retrofit on some.
doesn't work on bronze though & shift forks are often bronze cast.
 
Drain your oil into a clear glass container, hold it up to sunlight after it settles for a while, look for sparkles,
sparklers in your motor oil are bad :(
 
Just to clarify.... The teeth of the gears are not the issue. It is the engagement "dogs"
You won't find any metal in the oil, as this wear is happens over time is a "compression" of the metal and not "fragmenting"
 
The engagement dogs and/or the slots that those engage with, are one-piece with one or more of the gears on the shaft. It's generally going to affect two parts - whichever one has the engagement dogs, and whichever adjacent piece that they engage with.
 
Below is a picture of a worn second gear from a YZF600R.
Since the dogs are slightly rounded, there is a force on the second gear that tries to push it into neutral.
This puts a lot of force on the second gear shift fork and can damage (small indent) in the shift drum.

This is a great document that explains the issue and how to fix it:
http://www.frederickbecker.com/How_To/Second_Gear/DIY_2nd_Gear_Fix_RevB.pdf
 

Attachments

  • YZF600R_worn_second_Gear.jpg
    YZF600R_worn_second_Gear.jpg
    145.7 KB · Views: 13
These are the brass parts, shifter forks:
Fork_detail_1.JPG


Once bent or worn away they will no longer move the gears to the exact position necessary. If you find brass bits in your transmission oil this is where it came from.
 
I think you're gonna want your shift forks made out of something A LOT harder than brass.
If you find yellow metals (brass , bronze) it will be a bush or bearing.

I have never seen a shift fork made of anything but steel. Hardened steel.
 
bitzz said:
I think you're gonna want your shift forks made out of something A LOT harder than brass.
If you find yellow metals (brass , bronze) it will be a bush or bearing.

I have never seen a shift fork made of anything but steel. Hardened steel.
Click to expand...
Correct, brass was an incorrect term, should have read bronze, although brass is a major component in bronze.
No they are not normally cast in steel, they ride in direct contact to steel gears and slide on steel shafts, totally makes sense to cast them out of a bearing material (alloys that contain copper)

Forks.JPG
 
Last edited:
after you have replaced the gears, install a quick shifter, they save alot of wear and tear on transmission parts
 
After 2nd gear went on my CBR600 track bike, I installed the Factory Pro shift kit and it made all gear changes fell very solid and quick.
 
You must log in or register to reply here.

Back
Top Bottom