Disaster!

[Laverda Dave]

The CB250RSA went for it's MOT today, the test centre was 2 miles away. This was the first time I had ridden the finished bike.All went well, I noticed on the way there the carb needed some fine tuning but I thought I'd do that tomorrow.
I arrived home, parked up, had a cuppa and went back outside to the bike, disaster! A huge pool of oil was sitting underneath the engine and directly below the front chain sprocket.
When I put the bike on the bench and pull the cover off and chain sprocket I found the inner lip of the seal had been ripped as in the photo.
Does anyone have any idea what could cause this, the seal is a DS pattern part and the shaft was checked for any damage during cleaning and reassembly. It didn't leak previously either.
I guess this is going to be an engine out and lower crankcase half removal to replace the seal as it has an outer lip to sit in the cases.
I used Hondabond HT on the case halves, is this easy to remove, any special solvent required? The instructions only advise on application, not removal!

[mike the bike]

Disastrous as it sounds, there's no real damage done,  just a major embuggerance. If it's anything like the 400four, the bottom crankcase can be loosened enough to replace it.   Engine has to come out though.
Bad luck it happened while the sun is shining.

[hairygit]

So sorry for you, what a total pain in the butt! I assume genuine part is just not available now?

[Laverda Dave]

Hairy, I bought DS parts because I've used his pattern seals before with no issues.  What do they say, you pay your money and take your choice! I aways use genuine head gaskets, its going to be the same with seals from now on!
Mike, I'm hoping I can open the cases but unlike the 400 this engine has two balance shafts, one in the top case and one in the lower case, hopefully though I can open them enough to change the seal. Its removing the old Hondabond that will be the real issue, it sets like concrete, and I don't know how to remove it.
I'm amazed the seal didn't rip on the way to the MOT, it definitely went on the way back home.  I've just drained the oil, there was about 1 litre left, it shows how much oil pressure there is behind the seal. I'm so lucky I didn't go straight out for a ride, the engine would have siezed.

I was hoping to have posted photos of the finished bike today, not a photo of a ripped seal!

I'm off to the pub!

[Spitfire]

What a pain, but as you say it could have been worse if you had gone for a long ride.

Cheers

Dennis

[Nurse Julie]

That really is a shame. I bet you are gutted and I suppose it could happen to any of us regardless of whether the seal is genuine or pattern. The upside I suppose is that you have other bikes to ride so can still get out and about. Chin up.

[K2-K6]

What a pain after all the work to get it restored.

Similar task recently on a 750 crank seal in Australia on here,  successfully changed it without splitting cases. The seal locating extension that places it in the cases is ordinarily rubber and not supported by steel form internally so it's possible with care and lubrication to get them in without stripping the motor. Depends if you consider it worthwhile to try it.

They are not usually subjected to oil system pressure,  just crankcase internal low level variance. Shouldn't have been caused by that if venting is all ok.

[royhall]

Blimey what rotten luck, that's pattern parts for you.

Not usually recommended but worth a go at changing it in situ. I managed to change a lipped crank seal a while back after being told it was impossible.

Drilled two small holes in the seal (very carefully) then screwed in two self tappers. Used a small lever bar on the screws and unbelievably it popped right out. I coated the new one with Vaseline and tapped it in using a mallet and correct size socket as a drift. It went in fairly easily as well. At the worst your going to waste a new seal, at best it will go in well. Your going to have to strip the engine anyway so you may as well try. Just be careful with that drill.

Don't push anything down the centre of the seal, as even a tiny scratch on the shaft will cause premature failure of the new seal.

Good luck with it, must be heartbreaking. It's things like this that result in bikes being dumped under a cover in the back of the garage.

[Green1]

Things far more minor then that have caused me to abandon bikes for years at a time.

[Rob62]

Buy a seal without the outer-lip and press it in.... take care over the splines

[Nurse Julie]

If it were mine, I would be asking myself how did the damage occur?. It almost looks like something has hit it or caught it to cause the damage to the metal ring.

[UK Pete]

Bloody annoying but certainly worth trying to change in situ as described in other posts
pete

[Rob62]

Looking closely at that photo it looks as if the seal isn’t fully onto the shaft?.....like the shaft isn’t protruding far enough. Surely that can’t be the case...

[K2-K6]

Looking closely at that photo it looks as if the seal isn’t fully onto the shaft?.....like the shaft isn’t protruding far enough. Surely that can’t be the case...

I kept looking at that too Rob, I can't see from that angle in the photo enough detail to form an opinion.

Is the oil seal running on the shaft surface? or is that a sleeve that could be out of position? And can the shaft move in / out at all so that the rotating sprocket touched the face of the seal?

I know the sprocket is pulled up to the outside locator ring with two bolts usually,  but when fitted can you push the shaft in and out?

Edit; just a thought to check the sprocket bolts to make sure they can't touch the seal by being too long and protruding out the back of the sprocket if the holes aren't blind.

[Trigger]

I have been studying the pic for some time, something had caught it. Not sure about the sprocket bolts that K2 K6 has mentioned but, it needs investigating because you don't want it to happen again.