Well it does and should hold pressure, you just have to a make a judgement call for the moment at hand. If the pressure fell off in 30 seconds, that really would be bad. If the pressure never fell off, that would be Great. You have to look at readings and judge if they are the reason for the ROOT cause for you original problem.
As long as the pump can overwhelmingly delivery more pressure and volume to overcome any leakdown, then I would not consider it the cause for your bike issue. Since liquids don't compress, a static pressure drop with that small volume of fuel (1/4" hose 12" long), can't be more than a few of CC's over the course of 15 minutes.
Yes, going from 60 psi to 10 psi over 15 minutes certainly does mean there is some leakdown present. Can it be improved? I am sure it can. But is it the reason why your having a problem with the bike running poorly, probably not. To be on the safe side of the judgement call, I would run a dynamic gauge pressure test with the bike running. If it stays at the proper value (* see below) while giving it throttle, I would look elsewhere for your problem at hand.
Now once you find your root problem and correct it, and you want to make things perfect, I am sure you could improve the leakdown in the fuel system.
***One very important note: Before going any further, read this thread below starting at entry point #18. I was under the belief that all our FI systems ran at about 60 psi. It appears they do not on the early year bikes. I would confirm (per service manual) what the psi really should be for your exact bike. On the late bikes, it is 60 psi but it seems from reading this thread below that the early models are not the same.***
My back cylinder just quit working!!! - Harley Davidson Community
