Transmission Oil Maintenance

Water in the transmission oil.

I have taken in a couple of Trials motorcycles that have had or show signs of overheating the engine.

As a result and/or part of the overheating issue the rubber seal between the water pump and the transmission failed letting coolant from the bikes cooling system leak into the transmission oil. Rubber does not like to be overheated; it loses its flexibility, sealing ability and can even crack over time.

This was more of a problem in the past, seems like bikes in the late 90's and early 2000's needed a water pump seal change after about a year of riding. Seal materials have improved over the years and I haven't seen a water pump seal fail in awhile, but they still do fail, looking for this problem should be part of your bikes normal maintenance.

A Trials motorcycle should have the transmission oil changed on a regular basis, this could be several times a season up to monthly depending on how much riding and the type of riding you are doing with your bike. Changing transmission oil, regularly, helps with clutch action, longevity and wear of all parts in the trans. It flushes contamination from the transmission lessening the chances of contaminants setting into or on bearings, bushing, gears, etc., in the transmission.

The other reason for changing the transmission oil regularly is to see the color of the oil to determine if a water pump seal has failed.
Water in the oil will turn the oil a dirty milk color, the more water in the oil the whiter the oil will be draining from your transmission. The color of used oil coming from the trans should be dark in color, it's not unusual to see some very small metal sparkles in the used oil, that is why the oil is being changed, to dump the bad stuff out of the transmission.

If your transmission oil is light in color it may be time for a water pump seal change, this is a simple maintenance process, changing out a cheap part will save hundreds of dollars in damage due to an engine overheating due to loss of coolant in the radiator. Also as stated above water in the oil is a contaminant causing damage to all of the parts being lubricated by the transmission oil.

If you have questions about your bikes transmission oil or changing out your water pump seal contact Steve at Thumbs up Trials