1974 Sportster oil problem
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04-11-2015, 05:18 PM
Join Date: Sep 2014
Location: Texas
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#2
04-11-2015, 07:18 PM
This is known as "wet sumping". It is very common among IronHeads. I picked up the following from another IronHead forum; the original poster is very knowledgeable about IronHeads ...
OIL PUKING OUT ENGINE BREATHER
These seems to be a common question too. The most common causes of oil puking out the engine breather are listed below, in order of how common they are.
1. WET SUMPING
This is simply oil from the tank draining slowly back down into the crankcase while the bike is parked for any length of time. When you start the engine, the excess oil in the crankcase is fired out the breather, onto the floor, (or into your air-filter on post-79 models).
It is normal, if the bike has been parked for a week or more unused. Don't worry about it. Put a catch tray under the breather pipe before start up.
If it is too bad, you can put a new ball and spring in the check valve in the oil pump. See the workshop manual for that. Quite often though, it can just be tiny debris in the oil holding the ball valve ever so slightly off its seat.
The oil should stop puking after the engine runs a few minutes and pumps the excess oil back up into the tank.
2. OVER-FILLED OIL TANK
If the puking starts after you top you oil tank, this is probably the problem. If you fill the oil tank to the Full mark while some oil has wet-sumped down into the engine, you have too much oil in the system. The oil from the sump will be pumped back up to the tank, dribble down the vent tube to the timing cover, from where it is fired out the engine breather.
This puking will continue after initial start up until all the excess oil has been fired out, which can take a while.
The cure is to drain a quart or so out of the oil tank, run the engine for five minutes til the puking stops, then top up the oil tank to the full mark.
DO NOT be tempted to drain oil out of the sump by taking out the threaded drain plug under the front of the engine. These are notorious for stripping the threads and are very difficult to repair properly. In most cases the plug is factory installed and is not intended to ever be removed. Leave it alone.
3. WORN ENGINE
If your engine breather continues to puke oil or blow smoke after the above two things have been eliminated, your problem is most likely wear in the cylinders and heads.
Worn rings and even valve guides, can allow blowby of combustion gasses into the crankcase area, which then comes out the breather.
Usually this will be accompanied by smoke or oil coming out the exhaust pipes too.
A compression test will give some indication of top-end condition. Anything below 120psi is suspect, according to the factory manual. These bike will still run ok at even 100psi, but they will be down on power and consume oil, and blow fog out the breather pipe.[/QUOTE]
OIL PUKING OUT ENGINE BREATHER
These seems to be a common question too. The most common causes of oil puking out the engine breather are listed below, in order of how common they are.
1. WET SUMPING
This is simply oil from the tank draining slowly back down into the crankcase while the bike is parked for any length of time. When you start the engine, the excess oil in the crankcase is fired out the breather, onto the floor, (or into your air-filter on post-79 models).
It is normal, if the bike has been parked for a week or more unused. Don't worry about it. Put a catch tray under the breather pipe before start up.
If it is too bad, you can put a new ball and spring in the check valve in the oil pump. See the workshop manual for that. Quite often though, it can just be tiny debris in the oil holding the ball valve ever so slightly off its seat.
The oil should stop puking after the engine runs a few minutes and pumps the excess oil back up into the tank.
2. OVER-FILLED OIL TANK
If the puking starts after you top you oil tank, this is probably the problem. If you fill the oil tank to the Full mark while some oil has wet-sumped down into the engine, you have too much oil in the system. The oil from the sump will be pumped back up to the tank, dribble down the vent tube to the timing cover, from where it is fired out the engine breather.
This puking will continue after initial start up until all the excess oil has been fired out, which can take a while.
The cure is to drain a quart or so out of the oil tank, run the engine for five minutes til the puking stops, then top up the oil tank to the full mark.
DO NOT be tempted to drain oil out of the sump by taking out the threaded drain plug under the front of the engine. These are notorious for stripping the threads and are very difficult to repair properly. In most cases the plug is factory installed and is not intended to ever be removed. Leave it alone.
3. WORN ENGINE
If your engine breather continues to puke oil or blow smoke after the above two things have been eliminated, your problem is most likely wear in the cylinders and heads.
Worn rings and even valve guides, can allow blowby of combustion gasses into the crankcase area, which then comes out the breather.
Usually this will be accompanied by smoke or oil coming out the exhaust pipes too.
A compression test will give some indication of top-end condition. Anything below 120psi is suspect, according to the factory manual. These bike will still run ok at even 100psi, but they will be down on power and consume oil, and blow fog out the breather pipe.[/QUOTE]
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