Hi all

Among other problems, I have discovered that my newly acquired MC21 is leaking copius amounts of oil from the gearbox output (sprocket) shaft seal. I'm hoping that it's simply worn and an easy replacement but being an NSR newbie I have a couple of questions:

I'm assuming the seal can simply be replaced (ie: the old one pulled out and the new one slipped over the output shaft) without removing the gearbox? Am I right?

Is a leaking seal generally indicative of other gearbox probs - worn bearings etc?

Any pointers very welcome

Cheers

Wb

It's possible that the seal's just worn out. Maybe the bike was sitting around a while. This can dry the seal out, which then goes brittle and starts to spew juice out.

Another possiblity is that the gearbox has been overhauled, and when it was refitted, the countershaft caught on the seal tensioning spring and pulled it off, or worse, tore the lip of the seal.

Either way, you can change this seal without removing even the gear oil.

Very carefully drill a couple of small holes 180 degrees apart in the seal. Thread a couple of sekf tapping screws in just deep enough to get purchase. Grab the screws with some meaty pliers and yank that puppy out.

Fitting the new seal is a simple task, just be careful sliding the seal onto the countershaft so as not to damage it. Then tap it home making sure it goes in squarely.

Job done.

Or you could use a seal puller
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1995 A kit TZ 250
1994 Rothmans NSR 300sp SOLD
1998 RM 250 freestyle/motorcross
1998 Meathanol burning CR 500 AF super retard/motorcross/sand dunes/play bike

Or you could use a seal puller

What is that ?

I just found out that I have a leaking gasket too. Was inspected at a trackday today.
_________________
Poul
"If Life Gets Boring, Risk It!"
MC21SE, KISS box
MC21SP, HRC box, racing loom

Thanks fella's

I've just got back in, but I'd already resorted to the self-tappers method mentioned by Matt - the seal came out no problem. My semi-local bike spares shop had the right size seal in stock so I'll slip it in tomorrow and hopefully that's another in the pretty long list of jobs sorted.

The kindly Racer38 has offered me a 3-way joint on loan so I'll hopefully get the poerjets hooked up as they should be tomorrow too and then I can try to figure out what's up with the carburation/intake that's causing the erratic idle and generally pretty poor running.

Cheers

Wb

kolewski wrote:Or you could use a seal puller

Or the HRC claw hammer, with screwdriver attachment

OK. I very carefully installed the replacement seal (taped the splines and lubed the lip before sliding on. No problem. Just taken it for a test ride though and sure enough it's leaking copiously from the seal again So I have a couple of questions:

1. can anyone give me the exact dimensions of the OEM honda seal? The one fitted, and therefore the one I've replaced, was a 25/45/7. Acording to the receipts I have with it, the motor was completely rebuilt less than a year ago, so I'm wondering if the builder used the wrong seal and I've simply replicated their mistake by buying a seal of the same dimensions? The 7mm wide seal seems to sit a little recessed into the hole in the engine cover, and on closer inspection of the shaft i'm thinking maybe the oil feed whole on the outside of the bearing is nicking the seal (the lip of which should maybe sit further out on the shaft if the OEM seal is wider?)

2. Should there be about .5 - 1mm of lateral (ie: in & out) play in the shaft? I can pull it out that much, but there is no sideways movement at all and its rotation is very smooth. I'm assuming therefore that this is OK, but as this is my first foray into an NSR 'box I thought I should ask.

I'd really apprciate any help/pointers at all with this as it's impossible to properly sort the carburation etc. if I can't ride the bike to check things. I can't seem to access the online parts book either so I don't know if the info is in there? I get the main screen up but nothing happens when I click the links to the different pages for any of the models? Anyone have any ideas on this? I'd really appreciate it if anyone who can access teh manual could post up the relevant page on this thread.

I have ordered a new OEM seal from Apex leisure but I'm told it could be up to a fortnight before it arrives, so if I can fix it with a generic seal that would allow me to hopefully get the thing running and riding properly before then - enjoy the sunshine and all that...

I did notice quite an improvemnet from the general tinkering and tidying I've done so far on my short run - before the oil all over my boot wiped the smile off my face ) Backing off the preload, rebound and compression adjusters so that verything wasn't set to maximum has certainly helped the handling, and it's running quite a bit better than it was too. Just need to get this seal sorted so that I can give it a sound thrashing to see how it compares with my beloved TZR250R 3XV's - very unfavourably at the moment I'm afraid to say, but I hope to be able to revise this opinion...

Plesae help me...

Wb

From the parts manual

33 91207-KV3-830 Oil seal 23x45x7
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Poul
"If Life Gets Boring, Risk It!"
MC21SE, KISS box
MC21SP, HRC box, racing loom

I'm not sure, but I think you need some java or something for the parts book to work. Try these direct links

http://workshop.nsr-world.com/11kv3lj7/2FK11KV3LJ7/Pic/F3.jpg



http://workshop.nsr-world.com/11kv3lj7/2FK11KV3LJ7/F3.html
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Poul
"If Life Gets Boring, Risk It!"
MC21SE, KISS box
MC21SP, HRC box, racing loom

Ah, so maybe the problem lies not with the depth of the seal but with the inside diameter being 2mm to big .

It didn't look particualrly oversize when i slipped it on though... Can anyone confirm that that part number is for the MC21 gearbox - or are they all the same?

Thanks for the links, pbekkerh. I have up to date Java plug-ins. I think . i wonderuif my firwall is the prob? I'll try switching it off.

Thanks again for the info.

Wb

Can anyone confirm that that part number is for the MC21 gearbox

I took it of course from the MC21 parts.
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Poul
"If Life Gets Boring, Risk It!"
MC21SE, KISS box
MC21SP, HRC box, racing loom

OK. Thanks. I thought it would be a good idea to check. It's very frustrating not being able to check through the on-line manual myself.

I'll pick up a new seal with a 23mm diameter early next week and try again...

Best wishes

Wb

It's very frustrating not being able to check through the on-line manual myself.

Its available in paper form too.
_________________
Poul
"If Life Gets Boring, Risk It!"
MC21SE, KISS box
MC21SP, HRC box, racing loom

Just a thought, but have you checked the gearbox breather pipe?
If the breather is blocked it will force the oil out no matter what seal you fit.

Not checked the breather , but will do. Cheers

Wb