crankshaft oil seal

It looks as though my crankshaft rear oil seal has gone . Oil dripping from bellhousing drain after a short run.
What is the likelyhood of getting oil on the clutch plate
As I’m due to go to Snetterton on Sun??

I would think you will be OK for Sunday. I’m guessing it isn’t pissing out?? The flywheel is inbetween the crank shaft oil seal and the clutch, so that will act as a sheild. Wants sorting though!


Pissing out so wont be at Snetterton to cover you all in oil.
Sinclairs it is then…should I uprate the clutch?

should I uprate the clutch?

Yes, AP is working nicely for me.


I have the AP clutch as well and it is excellent. At the end of the day if you are paying someone to do the work, then while the gearbox is off you might as well get them to put a clutch in, as it will save you loads of labour if you have to have the box off again.

I mean they are going to have to take the clutch off to get the fly wheel off to then change the seal, so you should not incur ANY extra labour cahrges for fitting a new clutch.


All done and new clutch fitted…sinclairs say this oil seal failure is rare…
Anyway dont tell 'er indoors about the bill !!!
She will go off and buy some more shoes…
Looking forward to Donnington .
See you all there

It is NOT rare. It is an inherent issue with the K and ovalizing the cylinder liners. This creates pressure in the crank and that pressure has to go somewhere so it goes through the crankshaft seal.

Only way to stop it is to vent the crank.

Or fit a dry sump.

Or not get oval liners to start with

The crankcase is vented… All production K’s have PCV, this is a mandatory fitment due to EU regulations. Even with only 1% leakage past the rings (an implausibly low figure) the engine will generate 18cc of blow-by per engine cycle, multiply this by several thousand RPM and you will see how much volume the crankcase ventilation system has to deal with.

Part of the reason for crankcase seal problems is the poor fit of the seal due to machining tolerances, as the engine expands with heat the seal can lose its grip on the housing and since it relies only on the precision of fit to retain it then a significant number are spun out of/work out of the housing. A simple solution is to retain the seal with a little silicone sealant or to clamp it in with retaining bolts.


By venting crank I believe you mean the crankcase ?
if so how can this be done? as no doubt there is /are vent pipes already there.
thanks guys for advice… Now come on sign up for Donnington…

AFAIK the only venting is only internally to the head and then with the two hole that should go to the vaccuum in the TB’s.

The thing is that when you install a catch tank you normally eliminate that vaccuum and that’s the beginning of the problems.
A dry sump should restore harmony or like Dave says, try to be delicta on fitting the seals.
Better seals would help as well. I know Simon Erland’s engines have an upgraded seal.