New to Harley and currently have an 08' Nightster 1200. I have read/heard from numerous people that they run their oil low to avoid blow by of dirty air back into the crank case. I will be setting up an external breather system...But, how low do you all run your oil? I have heard people say they run with .5qt less than recommended. Any advice?

 

I run mine half way up the dipstick when measured warm

 

I run mine at the full mark, this is my 5th Sportster and I have never had a issue running the oil level there. If your getting alot of oil blow by, I doubt its from running the correct amount of oil.

 

Blow-by has nothing to do with the level of oil in the tank. If you have the tank too full, then you can get overflow from the tank itself.
Generally keep it half-way up the dipstick when warm.

 

I run mine 3/4 of the way up and never had a problem.

 

Yep, I accidently overfilled the oil and it overflowed the tank on my 1200C. I siphoned off the excess.

 

With my experience I disagree with some saying levels don't cause excessive blow by. If I run mine with the oil filled up to the full mark, my slobber box will fill up berry quickly if I'm running her hard and then it's down my pipes. I run mine a little above half on the safe mark and don't have the issue. Maybe its just mine but a buddy told me to try it and it works for me. Now long fast runs, I'll still make a little mess but not nearly as much.

 

Thanks for the replies. Going to do the oil soon on it and had seen different opinions. I’ll see how it does halfway up the dip stick.

 

I would say you may have other issues causing that. Bad umbrella valves maybe. My bike is 110 HP. I can put the level on the full mark and do 7400 rpm runs and wont have hardly any oil on the filter of my external breather. Know others that are the same.

 

I don't run mine low at all. I run it where the manual says to, which is anywhere between the add oil mark and the midway to full mark. Of course, HD in their normal confusing way states that the best place to run the oil level is NOT at the full mark, but below it.
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Information directly from the Harley Manual.


"If oil is at or below the lower mark, add only enough oil to bring the level to a point between the two arrows on the dipstick."

"Do not overfill the oil tank. Doing so can result in oil carryover to the air cleaner leading to equipment damage and/or equipment malfunction."

"Refer to table 25 . Always use the proper grade of oil for the lowest expected air temperature before the next scheduled oil change."



Also, to reduce the amount of "blow-by" run the viscosity oil recommended in your manual for the temps you are riding in.







External Breather Systems LINK