I have a slight problem with my scooter. It is a 2002 model Yamaha majesty 125cc 4 stroke engine with 18500 miles on the clock. I noticed engine oil seeping down the side of the engine (where the plastic cover is for the belt).
I checked the oil and it was slightly low, but nothing unusual. An AA patrol came out and found oil was entering the air filter housing, which he drained off. It seemed to be coming through the breather hose. There was about a pint of oil there.
He noticed at the end of the breather hose was a screw that comes out and drains any excess oil in the hose which seemed to have over flowed.
He suggested that the engine is worn. This cannot be the case because there is no smoke from the engine under heavy acceleration. Also, the engine oil has been changed very frequently.
This has only occurred after using the bike at high speed i.e. almost full throttle along the carriageway for about 30 miles.
Can anyone suggest what this may be, and should I be worried about this?
Your help will be appreciated.
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I'd guess either you oil is over filled or the AA man was right about wear. If your bores/rings are worn then combustion pressure gets in the crankcase and the only way out is via the breather.
Dribbles from the pipe is normal - but a PINT!
Blowby doesn't usually cause smokey exhausts - thats valve stem seals.
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I may have overfilled the oil slightly over the two years I have owned it. But what I am unsure about is the fact that when the oil escaped through the breather, on checking the oil the level drops below the maximum mark slightly. Shouldn?t it just stick at the maximum level?
Also, will slight overfilling cause any lasting damage? If I continue to top up only to the maximum mark and never over fill, should this problem occur again if it is an overfilling problem?
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If you're losing oil through the breather then the level must drop.
Overfilling can be harmful if the level is high enough for things like the crank to contact the oil and churn it up. It ends up frothy and the oil pump can't pump it round.
How often do you do these flatout, wide open throttle 30 mile runs?
I can see things getting a bit hot on a poor old 125.
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I go almost full throttle about once or twice a week. Of course, the engine is always warm at higher speeds.
Now that the engine oil level has dropped, which seems to have gone through the breather, it seems to be a little lower than the max level on the dip stick. Should I top it up, or let it stay and see if the level reduces any more?
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I'd top it up to max and then keep an eye on it.
Make sure you're checking it as recommended in the handbook. Bikes and scoots vary - some say when cold, some say after 1 minute running. Usually on a level rather than tipped over on a sidestand.
However, if you check it the same each time, it should show if you're losing oil or not.
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It turns out that the AA technician was wrong. On scooters, it has a tube that runs down that is similar to the breather but it isn't. It is an environmental thing to have the tube closed and hence it overflowed. It should have been emptied once in a while at service
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I have a similar tube to this on my Honda CB125 twin. Every once in a while you have to pinch the end of the tube to open it and drain out any oil.
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