This week Nick Prince talks us through a few tips to consider when fitting seals in his \’Something for the weekend\’ series. He also falls foul to Mrs Prince\’s wrath after stealing her hairdryer.
I\’ve found with the introduction of viton seals and with scooter shops doing their own version of the drive side oil seal plate it has actually thrown up its own challenges.
Firstly you have to heat the crank casing, with a flame to no more than spit temperature (if you spit on it and it sizzles) once its this hot its ready to take the bearing.
Tip: store your bearings in the freezer- because it helps them to contract.
If you look at the engine casing in this picture you can see the main bearing has a seal in the bearing. If you use sealed bearings then only leave in the seal that faces the crank. Remove the one from sprocket side of the bearing with a screwdriver so that it is free to be lubricated by the oil in the gear box.
This is where you can be caught out with Indian crankcases as the MB drive side oil seal plates I use are superior quality to any standard ones. These are made of steel and have little chance of warping unlike the standard aluminium one which can warp and lead to gearbox oil passing through into the crankcase.
However the new MB drive plates are thinner than the standard ones and when you tighten up the drive side plate the bolts can bottom out and give the impression that the drive side plate is fully home. To combat this I screw the bolts in, then do a visual check of the length of the bolts and if they haven\’t gone all the way home they stand slightly proud. Usually I find it tends to be only one bolt that stands proud.
So remove the \’proud\’ bolts, clean out the bolt hole making sure there\’s no debris in there, (for example old Loctite) replace the bolts and if they still do not go \’home\’ see how much thread is proud.
Take the bolts out and wind a nut on to the bolt, then trim a wee bit off the end of the bolt with a saw, linisher or grinder, then unscrew the nut – this tidies the thread up where you have cut a bit off. Clean up the end afterwards with a file.
Replace the bolts and they should now go all the way \’home\’. Do a visual check to make sure. I know it poses the question “how much can I trim off a bolt before it becomes unsafe?” If you measure the length of the thread on the bolt it should be 12mm before trimming and I personally have gone as low as 10mm and never had any problems.
Now its time to put the oil seal plate on, I don’t use any sealant but I know others prefer to so its your choice. Put the gasket on, then the drive side plate on, put Loctite on your bolts (use the weakest type), remembering the corresponding hole for each one, make sure you get any trimmed bolts in the right holes! Now your drive side plate should be in place.
Look at this picture of different cranks and the different tapers where the drive side seal fits. This can tear or damage the seal, depending on the taper and certainly on a viton seal, which are not quite as flexible as Rolf seals, so a specialist piece of equipment required – a hairdryer!
Warm the seal with the hairdryer , get the seal quite warm as this makes it more flexible, then place a bit of grease or two-stroke oil on the drive side of the crank where the seal sits. Put the crank in the crank casing, turn the crank backwards and forwards slightly, then apply a crank puller and pull the crank in slowly, gently rocking the crank backwards and forwards until the crank is \’home\’. You will feel when it is home and you can do a visual check as well.
Then apply your mag housing gasket using a gasket sealer of your choice. Then heat the mag housing seal once again using the hairdryer.
Danger!
Warning you need to ask permission of the hairdryers owner prior to use, as when the workshop one broke down and permission was not sought I received a very angry phone call. I\’m in the dog house again!
Words and photos: Nick Prince
Crankshaft Puller Tool
Nick mentions using a crankshaft puller in his article. It just so happens that Casa Performance have a new tool out that they developed from one of my ideas for doing just that job, so here\’s a SLUK exclusive first showing of what it is and how it works in the video below.
VIDEO: New RLC Lambretta crankshaft fitting tool
You can buy this double-use tool (it also fits seals to the CasaCase) at your local Casa Performance dealer, or you can buy the nattily-named X231b direct from Rimini Lambretta Centre here for £26.20 (€30).
The tool works like the Innocenti one and we\’ll be doing a full feature on it in the future.
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