Yamaha RXS100 - Crankshaft Oil seal

hjdowning · L Plate Warrior Joined: 24 Feb 2019 Karma :

I have been trying to tidy up an old RXS100 that I've had sitting in a shed for years.

I noticed the gear oil level keeps dropping, but there is no puddle of oil under the bike. Would it be fair to assume the oil is leaking into the crankcase? The bike is very smokey which would support this theory?

I have removed the crankcase cover to gain access to the oil seal.
My questions are:

https://i.imgur.com/Ys14AFa.jpg
https://i.imgur.com/v6xt4zK.jpg

Pete. · Super Spammer Joined: 22 Aug 2006 Karma :

It's certainly possible though if the seal is shot then likely the bearing is too. Does it idle an run well? If it's sucking oil then I'd expect a poor idle.

Another option is the vertical joint in the cases. This has to be perfect to keep the crank case sealed. Sometimes there will be burrs raised on the casing where some monkey has levered them apart with a screwdriver etc.

Seeing as it's a fixer-upper anyway I would order two new main bearings and two new seals and a tin of gaskacinch or yamabond etc, split the case, check the faced for raised spots and remedy as required then rebuild it.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good Very Happy

hjdowning · L Plate Warrior Joined: 24 Feb 2019 Karma :

It does idle ok, and starts very easily. A friend who also has an RXS rode it and though it seemed under powered (I wouldn't know having never ridden one in good condition)

Regarding burrs, the bike has been sitting is a shed for 10+ year and before that it was a farm run about, I don't think anyone has ever had it apart. I guess I'll soon find out.

Thank you for your help. I'll get some bearing, seals and gaskets on order.

bikenut · World Chat Champion Joined: 21 Nov 2011 Karma :

dont forget No3.

you know of cmsnl and have a manual and the flywheel removing tool, only use the proper tool for removing the flywheel and when refitting, be carefull and dont "bend" the points!
____________________
nuts about bikes

bikenut · World Chat Champion Joined: 21 Nov 2011 Karma :

Also if its been burning gearbox oil for some time, the exhaust system starting at the exhaust port will need a good clean out. Does the exhaust gas "fizz" its way out of the exhaust pipe, as if its fighting its way out under quite a bit of pressure??

As its been a farm bike, is the air filter a mud pie?
____________________
nuts about bikes

hjdowning · L Plate Warrior Joined: 24 Feb 2019 Karma :

bikenut - I have not heard of cmsnl, now looking at their website, thank you.

I have ordered a flywheel removal tool, set of oil seals, the o ring, a pair of crankshaft bearings and a gasket set from Yambits, should be delivered today.

The exhaust was very gummed up, I think i burnt most of it out with a torch before I realised it was loosing oil, maybe ill need to do it again after re assembling the engine (if I remember how it goes back together).
The air filter is clean but the foam is starting to disintegrate, so will need replacing I suppose.

bikenut · World Chat Champion Joined: 21 Nov 2011 Karma :

cmsnl is great and free!!!

You have a manual?? there may be one on here, but cmsnl complements a manual anyways.

Take your time and ENJOY.

When assembling the engine/gearbox, do dry runs and check everything but remember the gearbox may seem "tight" due to no c/case gasket, so just nip the crews for these tests, then assemble with the gasket when you are absolutely sure all stuff is in the right place, just make sure all the shims/washers/distance pieces etc.etc.etc are in the right place and gear selection happens properly.

Gear selection is easier when either the output shaft and/or input shafts are rotated slightly whilst selecting gears, just like when the engine is running and the bike rolling.
____________________
nuts about bikes

bikenut · World Chat Champion Joined: 21 Nov 2011 Karma :

you have a torque wrench for the crank and clutch nuts, but also remember that these shafts can be "locked" for nut tightening when the engine is in the frame via the gearbox and rear brake. If these nuts are nipped tight during assembly, to check and tighten them properly when the engine is in the frame, unless you make your own special tools to lock them on the bench that is.
____________________
nuts about bikes