I've been riding for over 50 years and only recently learned I was missing out on something! No it isn't necessary. Even if we were to purge what oil can be got out, there will still be some trapped around the engine/trans/primary. Check the FSM and see the numbers for dry and wet fills - the difference between them is the oil we cannot get out without stripping and cleaning. So purging is futile IMHO!

 

124,000 miles on the current motor in my bike and have never "purged" the oil. I just change the oil and filter at 2,500 miles (half of a 5K service).

Would my engine last longer if I did the purge? I guess I'll never know now.

 

 

I have done it a few times. My oil filter is right up front and I leave it off and put a funnel under it and wait for the new looking oil to start coming out. As mentioned, probably a complete waste of time. But......

 

You should ALWAYS purge, else you will leave at least an entire litre of old oil in the system, thats 33% of the total oil.
Youtube Delboys garage harley oil change and watch the whole thing, he pumps out a whole litre out of it.

 

I`m gonna throw the BS flag on this one...

Disassemble one of these engines and see how much oil is in the crankcases, a few ounces, and maybe a few ounces in the oil lines.
An insignificant amount.
Purging the oil is a waste of oil and time.

 

Just watch the video, or this one instead, a whole quart of filthy black old oil.


Would you pour a pint of beer into a glass with 7oz of week old beer at the bottom? If you would then that would explain it.

 

FWIW your motor keeps around 16 oz of oil in it when you change the oil.
The reason you are getting a quart out is because of the new oil mixing with the old until it runs clear.
You can scavenge/purge the oil if it makes you happy or you can leave the old in to mix with the new.
I know of some bikes with more than 100k on them that have never been purged so I don't think it's as big a deal as you are trying to make it out to be.

 

Maybe not a big deal but doing a full oil change could be the difference between rebuilding an engine at 100k and rebuilding an engine at 125k, just for a few extra minutes doing things right.
When you change the oil in your car, do you go ahead and put 1 quart of the old oil back into the engine to save oil?
A motorcycle engine is no different, in fact much more critical due to higher temps and a wet clutch.

 

I purge on my EVO, mainly because it's easy, takes all of 1 minute extra time and no mess with the filter under the bike, so why not.

Now with the filter under the bike, the lines to and from the 10 row oil filter, I get about 3/4 a quart of dirty oil out, very little mixing, it changes color abruptly,
also makes me feel warm and fuzzy, and my beer taste better.

Now, do I do it on my other two bikes, hell no, I get pissed at the mess it makes just changing the oil filter with it's dumbass location, not as much oil left in the system as the EVO, and they're not on the return side.