Scooterotica

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

After 35 years, I should be good at this, but I'm not. Any advice on this basic requirement would be appreciated

all I do, and I know its going to sound like a cliche, is to use plenty of lubricant and slide the crank in slowly. Same for the mag housing.

Chris

^^^^^

What he said, but I do use a nice smear of grease and have found bits of pipe, etc. of the right diameter to drift the seals in without damaging them. Also, I always make sure the seal is warm. Not with heat but warmed in my hands as they seem a bit more supple when warm. Do you have the proper seal drifts Martin? As for the crank, again grease on both surfaces and easy does it with rotating the crank as I slide it in (Ohoooer, Matron)

Hi.I always use vasoline on the seal lips as this disperses once the engine gets hot.I then warm up the centre of drive side bearing with a hot air gun,crank should slide in nicely but remember to rotate at the same time.I do have a pulling sleeve that I use with the centre sprocket bolt to hold the crank in place to check clearances between drive side plate and crank web.

Dean

I made a sleeve which fitted over the end of the shaft (this was not a Lammy, but the idea could be applied)
You need to recess the inside to suit the shaft, but leave a small, thin lip which sits over the working surface the seal sits on. The seal slides up then off the end on to the working surface.
The outer surface is as polished as you can make it and tapers down to the outside, so the seal drops on and is only gradually deflected.
If possible, arrange it so it can be fixed with a bolt or stud so you don't have to faff with it moving.
If access is really tricky, you can make a knocker onerer - a big piece of tube with a flange to push squarely on the seal. This can be made to act as a stop too.

Plenty of rubber friendly lube.

I hope this doesn't all sound a bit more complicated than it is, but I did have access to a lathe and big chunks of metal.
Try a night school? Ask a mate?

In extremis, I have used a sheet of very thin plastic sheet, like an overhead projector film, wrapped round the shaft. You have to be very careful not to slice the edge of the seal though, which is why I made a few of the metal ones.

A lot of people rub their fingers round the lip of the seal, according to the bloke at the seal makers I was taken to, this is a no-no.

OK, there are some good tips here.

The idea of warming the seal with a hot-air gun (or hair dryer) prior to installing the crank is very sensible, but I also like the idea of the tapered sleeve to ease the crank into the seal. Fortunately, I have a small lathe and I could probably knock-up a sleeve out of ali. Ooo, I like making tools.

Keep them coming.

I am no expert, but if anything the lips of some of the modern seals seem less rigid than I remember the Rolf branded ones were, perhaps allowing the spring to be more easily displaced?

Also, does the strength/tension of the spring have anything to do with it?

I also put seals onto crank first and leave over night ..this helps with installing them too.

Dean

Some good advise here for you, I am not sure about heating the seal I would have thought it would soften it and let the spring pop out easier. You could smearing heavy grease or Vaseline into the seal to hold the spring in. Thanks for the bits.

grease or oil the seal and keep rotating the crank as you pull it into place then as you push down the mag flange.