I presently own a 125cc motorcycle with a 4 stroke engine. It has covered 21,000 miles to date in two years and I am having a slight problem. When I take the bike for a journey of high speed (i.e. 60mph plus), if I travel around 100 miles the bike breathes excessively and engine oil comes out through the breather hose. If I travel 120 miles at high speed, the oil goes from full to just above the min mark on the dip stick. However, around town riding and short bursts of riding at 60mph (i.e. for 20 miles) does not exhibit this problem and has used no oil to date with this type of riding.
I am worried because I have looked after this bike with very frequent oil changes and services with out fail, and hope this does not mean the end of this wonderfully reliable bike. I have never thrashed the bike from cold, and there is no smoke from the engine at all.
Your comments would be much appreciated.
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Please, someone must have some information. Any info would be appreciated!
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if I travel around 100 miles the bike breathes excessively and engine oil comes out through the breather hose.
Is it oil, or just oil vapour from where the oil is so hot after a long journey? If it is oil, and the breather pipe is in line with the back wheel, I would be very careful when going round corners or roundabouts. Beleive me, I'm speaking from experience of a few years ago when the rotary disc valve oil seal let go on my Yamaha FS1E and blew most of the contents of the gearbox out the pipe and over the back wheel. No mirrors so I didn't notice the commotion going on behind me. ie, loads of smoke bellowing outthe exhaust followed by grazed knees and elbows when I came off the bike on a roundabout.
Have you tried a different brand / viscosity of oil?
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It is oil coming out. It is interesting that I can manage about 50 miles of relatively high speed (from Brighton to Eastbourne and back) without this problem at all, with zero oil consumption. However, if I try the M23 and M25 to London and back at very high speed (for the bike anyway), I loose a lot of oil which comes out through the breather.
If I am to try a different oil, what would be suggested. I have always used a 10w40 semi sythetic since new and have had no problem of this before.
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I doubt it is a worn motor. I have oil changes every 1000 miles, it emits no smoke at all, uses no oil in town or journeys below 50 miles all round and the exhaust is not sooty at all.
I am very confused by this problem.
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If I am to try a different oil, what would be suggested.
What does the manual / dealer recommend? Is it different to what you're currently using?
I have always used a 10w40 semi sythetic since new.
Without knowing for sure, I would have thought using synthetic oil in a small motorbike engine would be an unnecessary expense. Most people I know with small bikes use mineral oil.
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Normally, I would expect this heavy breathing to be blowing past the rings, and pressurising the crancase.
It may be that your long journey, allows the engine to get hot so that the tolelerances expand and allow slightly less than perfect cylinder sealing.
Does it still do this on cold / rainy days?
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Only general advice. If you do a lot of short trips the breathers may be partially blocked allowing some crankcase pressurisation (check Haynes manual for location of all breather systems). Some bikes IIRC have complicated breathers that open and shut with crank revolution.
Check engine compression with a gauge when hot.
Sorry to be vague. A new piston and rings may be all that is needed if the bore is plated.
--
I wasna fu but just had plenty.
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I read the haynes manual for scooters and there is no information about the breather system. It says to empty the breather as a matter of maintainance, and that is all. Perhaps it is just a thing with scooters, that at high speed (8000rpm), they just breath and for that reason there is a breather pipe with space behind the air filter to keep the material until emptied.
My garage checked compression, and it is fine. When I open the oil cap when the engine is running, no air comes out. My mechanic in Brighton (Gerry Ingram) says all bike breath like this, and assured me it is not a worn engine.
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