Took the bike out today for a first ride of the season. Great to get out in the fresh air and check out my workmanship from winter projects.

Weird thing was when I got home and went to check to the oil level on the dipstick, I heard a definite vacuum "sucking" noise when I was unscrewing the cap.

I don't recall ever experiencing this.

Anyone ever have this happen?


SJK

 

Try it again, this time let the bike sit for a few minutes after turning it off before checking or better yet, check the oil when cold. I personally find I get a more accurate reading when cold.

You probably had some vapor lock, I know that is not the correct term but I think you will get my meaning

 

Thanks for the reply.

The bike had probably cooled off for 15 - 20 minutes when I had that vapor lock sensation occur. I checked a few hours later and it happened again, but to a lesser degree.

One modification that I made over the winter was the installation of a DK Customs external breather system. Not sure how or if that could cause it. At the moment I'm going through the Service Manual reading about 'umbrella valves' (and a warning from the MoCo about how the installation of external breathers could cause some issue with those 'umbrella valves'.

It's late...and I'm tired. I'll re-read this stuff tomorrow.


SJK

 

Try this, e-mail DK Customs explain to them about the external breather system mod, explain to them what's happening and the statement in the HD service manual. It's my understanding they have done a lot of testing on this mod. Please post their reply, a lot of the users here have done that mod and there hasn't been any problems.

 

Yeah, I was planning to reach out to DK Customs (but probably by phone) to see what they had to say.

I reached out to the group here to see if anyone had ever experienced anything similar, or knew more about crankcase venting than I did.


I'll report back with anything that might be useful after I talk to DK.


SJK

 

I’m running the external breathers as well and every once in awhile there will be a little sucking sound when pulling the dipstick out but it sounds more of just the rubber sticking then any sort of vacuum within the breather system.

letting your motor breathe will not effect the breather valves at all , Harley will say not to because of emissions nothing more.

the oil system is not a closed locked down system, it has to breathe...my guess is that you might be over filled. When it comes to oil level, it’s better to be under then over....

 

I heard back from Dwayne at DK Custom (THANKS DWAYNE!!!), sucked about 8OZ of oil out, went for a ride today and no suction noise. My usual fill up has been 2.5 quarts with the filter. Looks like from now on I'll go with 2.25 quarts.

SJK

 

Good Job!!!!

 

So I guessed right...you’d of thunked it...

 

Seems like a thanks to crusader is in order?