Looking at some 17 and 18 used bikes. My initial thought was to stay away from 17's with the idea that 18's might be alittle better? The bikes are in the 6K to 18K mile range. Anyway to tell if the bike has had issues with sumping?

 

Not really other than listening for noises and lack of response. Best way would be ride it in an aggressive manner and hit higher RPM, you'll get a pretty good idea.

 

You can ask for the warranty history. You can ride them and if they run good they run good. If you are worried about sumping and or Transfer, have the dealer upgrade the pump and back plate along with the Primary vent to current production. then enjoy the ride.

 

If you are talking about true sumping, that is the transfer of engine oil into the primary housing. Most of the 17-18 bikes had a transfer problem with trans fluid into the primary and Harley came up with a fix for that...It was a inner primary vent. My bike had that fix installed about a month ago and has had no noticeable transfer since.
Just ask the dealer if the new inner primary vent has been installed on the bikes your looking for.

 

The 18's were built no differently than the 17's, so don't expect a difference there. As stated, review the warranty history with the dealer for any bike you're interested in, and buy whatever fits your desire and budget. Keep in mind the vast majority of those bikes did not and will not sump, despite what the forums might indicate.

 

Maybe you just typed this incorrectly but that isn't sumping. Sumping is when the engine oil gets trapped in the engine case and will not return normally to the oil pan.

 

I would be more comfortable with a used m8 that was pretty much stock with slipons being the only mechanical mod. If you have aftermarket tuners/different cams etc, then the risk goes up. My 2017 cvo limited has been rock solid dependable for the past 2 years and has been ridden hard and often 2up for 20k miles.

 

2 simple methods to check if an M8 bike has or will sump.

1) As already stated, ask the owner for permission to take the bike’s VIN # to any dealer and ask for the service records

2) Ask the owner if you can take the bike for a 45min to 1hr test ride. Check the oil level before you leave and then check it when you return after a “healthy” ride. If the dipstick oil level from before to after is more than 2-3 dots lower, then politely RUN away from the bike.

 

Does sumping ever do permanent damage though ? I know they slow down on their own, from so much oil in the crankcase, but aren't the journals at that time getting a lot of air from the oil pump ? Or is there so much in the crankcase, it doesn't make a difference ? Plenty of oil anyway, so nothing got scored... ?

 

Yes, if a bike’s sumping is extensive and you continue riding, then you can definitely cause catastrophic damage (and not even know it til its too late). There are no engine lights that come on from sumping and since HD doesn’t want riders to know the engine temp, its easy to cause serious damage without any signs of a problem till its too late.

Sumping can be very subtle at first and for someone that has never experienced it, its doubtful they would be able to detect it, til the bike has lost serious power. At that point, the damage may already be done.

The problem is TOO much oil which causes massive friction around the crank which in turn creates enormous heat. Heat can kill an engine. I had 3 M8 engines with bearing damage that required the engines to be replaced under warranty.