Which NSR model is this gearbox from?

**Fri Sep 23, 2005 6:15 am » Post: #1 » Download Post**

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Jerry Lai
NSR250 [MC21SP]

**Fri Sep 23, 2005 7:01 am » Post: #2 » Download Post**

A wet clutch MC21 by the looks of it.

Need to see the gear selector shaft to be sure.

Ratios are the same thru all MC21 models and years.

**Fri Sep 23, 2005 7:25 am » Post: #3 » Download Post**

Should I get this as a spare even though I have a dry clutch NSR? Could I use the gears out of that thing?
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Jerry Lai
NSR250 [MC21SP]

**Fri Sep 23, 2005 7:50 am » Post: #4 » Download Post**

Can't say as I've ever heard of an NSR gearbox failing. I'm sure there must have been, but never heard of it, so it can't be common. How much junk space do you have in your garage?
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

**Fri Sep 23, 2005 8:37 am » Post: #5 » Download Post**

It's selling for pretty cheap (AUS$50), so I thought "why not?" if it fits. Laughing

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Jerry Lai
NSR250 [MC21SP]

**Fri Sep 23, 2005 9:33 am » Post: #6 » Download Post**

Not a bad price i got a spare as well for my R came from a bike with little miles on but mine is in bits i got the clutch Too, i paid £50 for mine but i only got it for spares incase i strip a gear or break something.. 50AU$ seems a good price and if you can afford it why not. With sods Law your almost putting a garautee on you current bike not breaking, SELL it and the day after will see your gear box in bits LOL you always break bits you dont have spares for... Razz

**Mon Sep 26, 2005 7:23 am » Post: #7 » Download Post**

When I raced and SS NSR we had an F3 box fitted. Never had a problem.

The following year changed to SP so I had to run the stock box. Went through three in a season.

The locating dogs are made of cheese and once my club foot had missed a couple of ratios the dogs round off and it's just a story of woe from then on.

**Mon Sep 26, 2005 1:48 pm » Post: #8 » Download Post**

Intresting matt, 3rd on my box at the mo just needs a tiny bit of preasure from my foot back the throttle very slightly and it jumps in ......mmmmm glad i got my spare box now, could be me but maybe itll need changing.

**Tue Sep 27, 2005 7:35 am » Post: #9 » Download Post**

The best solution is to be a bit more careful with the gear changes (unlike me), make sure that the levers etc are all in good condition with not too much slop, and good tranny oil. Then you'll probably have many years of happy cog swapping.

The F3 box is just like the RS250 and many other race boxes in that the dogs are undercut, so the gears mesh together firmly and they ain't going anywhere.

**Tue Sep 27, 2005 7:58 am » Post: #10 » Download Post**

Just what is an 'undercut'?

Heard it said lots, but never seen a picture of what it actually means...
_________________
MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

**Tue Sep 27, 2005 2:02 pm » Post: #11 » Download Post**

Undercut, means that the locating dogs are machined at an angle so that when the dogs mesh together they actually try to pull the gears together. this helps the gears locate faster and aslo resists jumping.

Errrr, a picture would probably be better, but I'm crap at drawing. Andy's a bit of a Picasso so I'll leave it to him. I'm putting an F3 box in my 300, so I suppose I could take a pic of that and a comparison shot of the NSR box. Don't hold your breath though 'cos I've just left the workshop and I ain't going back into that dark room 'til dawn.