Yep, using Andy's strategy of keeping the reservoir topped up after each ride so as to have an early warning of the oil seal having gone south, I noticed a nearly dry reservoir and over-flowing transmission. I did a search and came up with this thread (and great pictures - I love pictures!) http://www.nsr250.net/forums/viewtopic.php?t=1192

But being a novice, I need more, so I'm hoping some kind soul(s) will give an elaborated step-by-step on this fix - just assume you are talking to a moron and that no detail is likely to be too small to mention. I've never pulled an oil pump out before so don't really know the sequence. I imagine we start by draining the transmission oil. Do I then drain the 2t main tank? If so, how exactly is this done without getting oil all over the place? Next, how exactly do I remove the oil pump, bleed the system,? etc. Sorry to be so remedial, but with no workshop manual or prior experience, I have to ask, or not ride, and the latter is even more painful. Thanks.
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-Jim
'93 MC21

You are right,drain the 2-t tank, you could use a couple of swarf free bolts to bung the pipework.for convenience ,if you prefer ,and leave what isn't in your gearbox there!.Drain the gearbox,remove the pipes from the oil pump.Detach the pump body,the shaft ,with detached seal,is your culprit.Use a sealant to seat the seal.Reassemble the oil pump and pipework,fill the 2-t tank,if drained, there is a bleed screw on the pump,open this and wait until you get a flow .refill the gearbox( new crush washer).Empty the fuel tank,put in a litre,-Imperial or U.S.?- of pre-mix(25-1)and fire it up.

WARNING!!!!!! on further inspection of those photo`s the 2nd picture down with the seal 1/2 way down the shaft is the wrong way round!!!!
the seal should be the other way round with the flat side facing outwards!!!

hope this helps......


cheers phil

Thanks guys, do keep those tips coming. Bushman, I would not have known to start out with premix, so you saved me there. I get the idea of doing this upon reflection...but how long do I need to run it before I can just put regular gas back in safely. And Phil, you've saved me too. Being very visual, I would have followed that picture and got it backwards -wouldn't be the first time!

A couple follow-ups.
1) To keep from draining (and wasting) the 2-T oil in the tank, can I use something like vice grips to pinch off the oil feed tube or would that likely bugger the tube?
2) if I was going to actually replace the seal, does the shaft pull straight out of the pump to allow the seal to be put on?
3) I've not got in there yet (still gathering info. and courage), so maybe it would be obvious once there, but where is the bleed screw? can it be seen in the pictures from the earier thread?
4) if I start with premix as directed, will this protect me from a less than perfect bleeding job, or do I need to worry about the bleeding part as much as I am, which is a lot!?

Thanks again for the help.
_________________
-Jim
'93 MC21

Jim wrote:
...do I need to worry about the bleeding part as much as I am, which is a lot!?

Jim wrote:
...does the shaft pull straight out of the pump to allow the seal to be put on?

Yes.

Jim wrote:
...where is the bleed screw?

Sorry about the poor scans, but it should help make the bleeding process pretty obvious.
_________________
Andy.
NSR-WORLD.COM

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Andy, this helps tons! Thanks!
_________________
-Jim
'93 MC21

Use swarf free bolts to block the pipework.You can fill the tank with petrol after running the motor ,on pre-mix,!!,for a few minutes.

Thanks, Bushman, bolts it is then. Once the Manco seal arrives (thanks Fenton for the part number), I'm going in!
_________________
-Jim
'93 MC21

Take lots (and I mean lots) of photos Jim, and write the proceedure up, and I will add it to the Site if you want?
_________________
Andy.
NSR-WORLD.COM

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Hah, I'm better at writing than I am at doing this sort of thing, so we'll likely end up with a very good description of how NOT to do this fix....but with enough pictures I suppose even that can be of some use to others! So I'll give it a try.
_________________
-Jim
'93 MC21

Don't worry... by the time I've fussed over it the original write-up will probably be unrecognisable!
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Andy.
NSR-WORLD.COM

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I dont want to hi-jack this topic, but if this problem is not fixed, what happens to the bike ?
IE - if the the 2T oil drains into the gearbox, what happens when the gearbox is full ?
I have a feeling this has happened to mine. After i got the the bike back together and back from a hopeless mechanic, i checked the gearbox to find oil spewing out of the filler cap once released. So i drained it thinking that he had over filled it. But i thought, how the hell could you get this much oil into it in the first place? As i took over 1 whole litre out !
However it doesn't seem to go through alot of 2T oil.
_________________
Winning isn't everything, but loosing isn't anything

My motor was damaged,one cylinder siezed.I didn't realise what had caused it until I opened the transmission filler cap!!It's the first thing I did i.e.affixed the seal,when I bought another MC21!

Okay, I'm in the middle of replacing the seal. Can someone tell me (quickly!) whether the shaft, upon install, just gets pushed back up into the housing containing the seal, or is it supposed to screw in somehow? It has threads on the end but it doesn't seem to grab anything, and I have visions of it just falling down into the transmission. Maybe it mates with gear in transmisson and that holds it in place? please let me know ASAP before I do something I'll regret!

Thanks.
_________________
-Jim
'93 MC21

They aren't threads on the end of the shaft, it's a worm (or screw) drive, similar to the drive on a steering rack to convert the drive through 90°. The shaft just pushes into place.

Don't forget the steel washer that sits in the hole in the transmission cover to stop the drive on the bottom of the shaft from tearing into the soft alloy.
_________________
Andy.
NSR-WORLD.COM

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