LCGB Forums

Jetset may well have popped through your door this morning with my latest oily rag article about Viton oil seals. By sheer coincidence, I was stripping the bottom end of my engine last night and discovered considerable damage to both main oil seals. The blame for one of the failures is related to bad fitting, where the drive side oil seal spring has popped out. Has anyone any crank-fitting advice to ensure that this doesn't re-occur, as I don't seem to be very good at fitting cranks into oil seals?

The photo shows how the drive side seal-spring sat across the lip, rather than in the groove, but the mag flange oil seal was very badly damaged, allowing the grease to escape resulting in damage to the bearing. This was a Racetour viton seal and the failure of the seal may or may not have been a fitting error.



If you wish to see this in more detail, click on the link below.

http://colchesterdvlc.co.uk/martin/images/oil_seal.jpg

Any advice on this basic requirement would be appreciated.


(BTW, the shielded drive-side bearing - with integral oil seal - did the job at keeping the gearbox oil separate from the crank, which is good)

This is a difficult one. I really don't like to jump in and say 'poor quality parts' as it is possible that the drive side one was due to a fitting issue. But on the mag side? Really difficult to cock that up. Were they fitted the correct way round? I always grease the oil seal lips and the crankshaft before fitting. I'm looking forward to others thoughts.

Paul

I always use the old seal and sit it on the new seal and tap it in. If necessary a large socket can be added. Remove the old seal before it goes in too deep and finish again with a large socket.And as previously said grease the seal and crank.

did you grease or oil the inside of the seal before putting crank in? lubricating the lip doesn't only help the seal to slip over the crank when inserted but also helps prevent the lip being ripped off when the engine is first started after rebuild especially if its a while between fitting the crank and starting the motor.
I never use racetour seals, used them once as they were readily available but had a bad experience so stick to rolph as never had problems with them before or after.

What I do To fit the crankshaft into the engine without damaging the soft rubber or lipping the seals which sometimes causes the springs to pop off.

The drive side,
I find Spinning the crank while pulling the crank in slowly with a pulling sleeve is the most effective way.

I don't grease the driveside oil-seal, insead I prefer to use fresh gear oil both on the crankshaft oilseal shoulder and on the oilseal itself.

When I'm fitting a crankshaft I find it best to spin the crankshaft and after every half turn of the drive bolt in the pulling sleeve I also jiggle the crankshaft up and down, I find this helps to slide the leading edge of the seal over the shoulder of the crankshaft.

It's only the last 6mm of pulling the crankshaft into the drive bearing that is really going to damage or effect the seal, because until this point the oil-seal is not fully in contact with the crank.

The mag side,
I grease the crank and the oils seal and locate the mag housing, next I gently push the mag housing home until I feel the slightest resistance, then once again I spin the crankshaft while applying very gentle pressure on the mag housing.

The mag housing will push on with very little pressure (thats if it's a good slide fit in the casing) that's once the seals slide over the crankshaft, which they will do as you spin the crankshaft. This is made much easier if the maghousing is a good slide fit into the engine case.

I use no heat when fitting the crank other than room temperature.

If Viton Oil-Seals are used I would not use a heat gun on the actual seals because Viton does have some serious health warnings.

I do use heat to fit the mag side bearing but I only heat the mag housing to around 100-150 C max.

I use MB's nylon seal drifts to fit both mag seals, these tools make it very easy to do right.

I fit the drive bearing by heating the casing to around 150 C and pulling it in with the bearing pulling/removing tool from Scooter restorations.

The drive seal I fit into the seal plate by hand then to make sure it's fully home I press the seal into the seal plate with a wooden block placed either side and the use of a vice.

But if you are fitting seals be very careful not to overheat or burn the seals if your using a heat gun.

Many thanks for the replies. I trust others find this advice as helpful as me.

Knowledge wrote: I trust others find this advice as helpful as me.

I sure do as I've never really been happy with the method I use and have had a few issues fitting viton seals also

Great thread