1991 Electra Glide Evo smoking at idle
HDF Community Team
Joined: Dec 2005
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From: NC USA
Do a compression test as mentioned before you take anything apart. Could save you some labor later on.
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3rd Gear
Joined: May 2026
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From: Denmark
The odometer shows 50,000 miles, but I honestly do not know how many times it has rolled over. Unfortunately, there is no service history available for the bike, so I am starting from scratch with the maintenance.
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3rd Gear
Joined: May 2026
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From: Denmark
I also suspect the valve guide seals could be the issue.
However, the carb seems to be tuned well; the spark plugs are not black or fouled. Over the last 300 miles I have averaged about 45 MPG, which I think is very decent for a bike this age.
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3rd Gear
Joined: May 2026
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From: Denmark
Yes that is correct, my bike has a hose with a small filter located under the transmission connected to that fitting. No oil mist entering the air cleaner.
HDF Community Team
Joined: Dec 2005
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From: NC USA
Remove the filter that is connected to the crankcase. They will stop up very easily and will not allow the engine to breathe.
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3rd Gear
Joined: May 2026
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From: Denmark
I have actually thought about that. I tested the breather filter by blowing through it and there is very little resistance, so I do not think it is causing any backpressure issues right now. However, I have been considering if that filter is even necessary since the hose is pointing downwards anyway.
Club Member
Joined: Apr 2011
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From: SE Louisiana
I'd take a look at the breather gear, it may have broken teeth and not turning.
Does it have adjustable pushrods?
Does it have adjustable pushrods?
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From: Honah Lee
I have actually thought about that. I tested the breather filter by blowing through it and there is very little resistance, so I do not think it is causing any backpressure issues right now. However, I have been considering if that filter is even necessary since the hose is pointing downwards anyway.
Put a dual range vacuum/pressure gage on that vent hose at idle briefly. See any bounce towards zero pressure
If you don't have a gage, you may still be able to fill a slight very brief vacuum especially if your geared rotary breather valve or it's bore is worn.
Fill or see any vacuum? That why the later Harley when they did away with the spinning geared breather vent valve in the cam chest and simplified it by put the one way poppet valves in the rocker boxes needed those one way out poppet valves.
That's why modified vents to the outside have a filter.
The later design poppet valves are one way out. Modifications from them to the outside probably still need a filter since the rubber valve ones may eventually fail. As designed, the hose from then is in the filtered air filter box area.
Even if you had a more modern head vent poppet valves, they shouldn't cause too much oil vapor in vent line unless engine has excess blowby from wear.
Last edited by Jackie Paper; Today at 08:00 AM.
HDF Community Team
Joined: Dec 2005
Posts: 5,394
Likes: 2,596
From: NC USA
I have actually thought about that. I tested the breather filter by blowing through it and there is very little resistance, so I do not think it is causing any backpressure issues right now. However, I have been considering if that filter is even necessary since the hose is pointing downwards anyway.