I looked at the bike today for the first time in a week. I was puzzled by a damp patch on the floor and investigated. Oil is dripping from the the drain hole in front of the stand assembly. I opened the gearbox plug which took a bit of force and was met with an audible hiss as air rushed in or out ( not sure which ). Has anybody got an idea which seals are gone before I start stripping? Also what are the risks from topping up the oil and continuing to use it while I order seals. Thanks in anticipation.
88KE

If the oil drips from the hole in the belly it could only be the seal on the gearbox input.
Could also be the seal to release pushrod, but unlikely....then you should have problem with a slipping
clutch a long time prior to this.

As you got vakum in your gearbox, it seems like the breather cap on the top of the gearbox also needs
to be checked.

Inge K.

Thanks Inge. I guess it possible a blocked breather has caused the problem - is there a risk to the clutch plates if I keep using it. (I've never stripped one before so this side of things is a big learning curve for me).
88

I first also did think that the blocked breather could have blown the seal but then found it unlikely.
When you getting pressure behind the seal the lips would be more tight around the shaft,
and I think it would seek out at the gaiter for the clutch relase mechanism at rear before blowing the seal.

But on the other hand it could be that the seal allready was well worn, and just did get some help from
the pressure.

It might also be an idea to remove the FD to check if any oil have entered from the output shaft.

The oil would be thrown into the bellhousing before reaching the clutch, so that`s no risk.

Inge K.

At a guess I'd say a blocked breather and when the pressure builds up with heat it pushes the oil out the weakest seal. When it cools back down it sucks in some air. Same thing happens with car diffs especially muddy 4x4's . As long as you check the oil regularly and your clutch doesn't start to slip you'd be safe to keep riding until you get time to fix it.

Thanks Steve. I was thinking along those lines myself but never having spilt a gearbox off one of these I can't visualise where loose oil will go. I just want to get a couple of hundred k's outof it next week as the family are away and I'm due a couple of days off so I'd planned a small trip.
88

I must go along the lines of a blocked breather I have found this many times on engines gearbox's and axles, as pressure builds up the oil will be forced out. I saw an example with an engine once the breather was blocked with the result that the dip stick was fired out of its tube.

BIG D

Update...

I got a couple of hours to to tidy the garage and get at this coz it's been buggin me. I drained the remaining oil and its got water contamination...



After removing the battery and tray I found the top of the gearbox had quite a bit of water on it (to the top of the ridges/Fins). I pulled out the breather pipe (arrowed red) from the hole (yellow circle). It seem to be a long way in there about 50mm and was hard to remove but when I eventually got it out it appeared to be clear. It's possible a lump of crud was on the end of it.

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A couple of question to those of you more experienced please..

i) Should the pipe be that far in and should there be something to seal it around the hole?

ii) what should I use to flush the gearbox to get rid of the contaminated oil?

Thanks as always.

88

The breather pipe should have a cap on the top, similar to the one on the FD (but wider, by memory).

This is what the breather pipe should look like:
It has the same part# as the one on the FD.



Inge K.

Thanks Inge. I just measured the hole which is 6mm (I.d) and the pipe is 6.5 (o.d.). But it looks like without that metal ring the pipe has worked it's way too far into the box and been blocked.
88

88KE wrote:Thanks Inge. I just measured the hole which is 6mm (I.d) and the pipe is 6.5 (o.d.). But it looks like without that metal ring the pipe has worked it's way too far into the box and been blocked.
88

88 that hole is not the breather if you have a good look you find it just goes through the casing and into the open space behind the swingarm. don't ask why or what I have never heard any explanation for it. The breather is almost under the starter motor and you can't even see it till you remove the starter.
You very obviously have water ingression which is getting boiled of when the oil gets hot because the lubrication is failing because of the water.
If that quantity of oil has come out of the gearbox via the front seal you will have oil on the clutch.
Solution is to remove the box and clutch clean the clutch but I would replace the driven plate and check the drive and pressur plate for warps etc replace the seals in the gearbox and check the bearings and replace if suspect because the bearings won't have been getting good lubrication with that honeycomb mix.
You may get away with fresh oil for now but I would say the clutch will fail in the future.

I better start stripping further K-Freak. That quantity of oil is what was left in the box so there's probably a bit less than half escaped or being forced out. I have a feeling this is a problem of my own making as, in my ignorance, I tried to blast away grime from the top and bottom of the box with the power washer. I've only done 200k since then so I might be lucky.

I'll pull the starter tomorrow night and check the breather if that tube's not it, then flush the box with clean oil and see if she'll hold up until I can assemble the parts needed to do a thorough job. Bloody typical that this would happen as soon as I plan a few days off with riding in mind (rant over....and breathe..)
88KE

Not a good idea to use a power washer on a bike, gets water into places where it shouldn't go.

K Freak wrote:88 that hole is not the breather if you have a good look you find it just goes through the casing and into the open space behind the swingarm. don't ask why or what I have never heard any explanation for it.

Battery breather tube.

Inge K.

I have a related problem (we are linked 88KE not just by the N11!). Gearbox oil leaks at the rubber gaiter at the back of the clutch push rod if the gear box is topped up with oil to the recommended level. It stops when the oil has reached a certain level. The gaiter has been replaced twice in the past 2 years. The breather pipe on top of the gear box is not blocked (thanks for that tip Inge). Two questions: how often should the gaiter need replacement? What is the pathway for gear box oil from the gear box to the gaiter on the clutch push rod end? Thanks in anticipation.

It`s quite normal that its oil present behind gaiter, as it ain`t any seal between the parts in front of the gaiter and the inside of the gearbox.
The gearbox oil is also lubricating the clutch release bearing, which is at the other end of the piston....
which is the first part you see when you remove the gaiter.

Probably you got a leak at the contact area between clutch actuator arm and the gaiter.
Take a look in this thread.

Inge K.

Many thanks Inge, and for the link to the earlier thread. I'll try cleaning and sealing the contact area.

A quick update: I pulled the starter motor and checked the breather - no visible blockage. I've refilled the box any will take it for spin in the next day or so to see if the leak is still there or if it was caused by steam from the contaminated oil, then drain the gearbox again.

As I was moving the coolant bottle out of the way the pipe split, perished! I'll trim back the pipe and refit tomorrow but what does everybody use instead of the crimped pipe clamps on the coolant pipes? Jubilee clips or fuel line clamps?
88

I simply use cable ties on those coolant bottle pipes.....there's no great pressure in them.

Paul.

sidecar paul wrote:I simply use cable ties on those coolant bottle pipes.....there's no great pressure in them.

Paul.

Cheers Paul, I was wondering if a cable tie would hold.
88

Put the bike back together this afternoon and took it for a good spin to get everthing hot. Not a drop under it, so it looks like its holding the oil & good to go for the few days off at least. I know from other experience the seal wont last long from here so I'll be ordering the bits to have on hand for a full strip down. After I get back.
88

sgmayhew wrote:Gearbox oil leaks at the rubber gaiter at the back of the clutch push rod if the gear box is topped up with oil to the recommended level.

To my earlier post about this I can add, that also an improperly adjusted clutch
cable can cause a leak.

Clutch cable adjustement....if the 75mm length is to far out, the actuating arm gets an awkward angle and the spring inside the gaiter gets an uneven
tension at gaiter against the sealing surface on the actuating arm.

Inge K.

You were spot on Inge. The clutch cable was too long. NOW I understand why the 75 mm length is so crucial. After cleaning the contact area and properly adjusting the cable, there has not been a trace of a leak in six days. Perhaps the gaiter will also last longer. Many thanks.

sgmayhew wrote:You were spot on Inge. The clutch cable was too long. NOW I understand why the 75 mm length is so crucial. After cleaning the contact area and properly adjusting the cable, there has not been a trace of a leak in six days. Perhaps the gaiter will also last longer. Many thanks.

Inge is a one man encyclopaedia! Good result SG.
88

sgmayhew wrote:NOW I understand why the 75 mm length is so crucial.

That`s not the real reason,...but a consequence of....when the cable is adjusted
to the correct lenght...the part of the actuator arm that is closest to the piston is at 90^o relative to the piston when the clutch lever is pulled all the way in......
and at its most effective working angle.

Inge K.