I recently had the heads on my 2014 Street Glide Special ported, polished, and decked .010". The bike also has Fueling 574 cams and cam chest plate, that were installed prior to the top end rebuild. After the work, I’ve started the motor twice and let it run until fully warmed up.

Here’s the issue: I’m getting a lot of pressure in the lower end. When I remove the oil fill cap, there’s a noticeable pressure release. If I leave the cap loose while running, it bounces around from the pressure.

Questions:

• Should I keep running it to allow the new piston rings to seat?
• Could something else be causing this?
• For reference, it does have new breathers installed.

I plan to run a compression test after the motor cools down. Any advice or insight would be appreciated!

 

While a compression test is great as an initial test, a leakdown test would be a better test for troubleshooting an over pressure issue.

 

Just my opinion but I would drive it reasonable to seat the rings.

If done right, rings will seat with in minutes of running.

I know Reasonable and Right have different meanings to everone.

Harley's owners manual recommended will work.

It more a guide line so if something was missed, it doesn't come apart at 100mph like some drive these bikes.

Not really anything to do with seating anything.

It's normal for the crankcase to be pressure pushes. That two large pistons pushing a full stroke of air out.

Now if there is excess blow by, a compression test will show that. Be sure motor is warm and throttle body is wide open.

A leak down really is just to find were the issue is if compression is low.

 

Hey, what do you know, I agree with Jackie...

Ride the motorcycle.

Do a compression test after you get some miles on it if it is using oil or performing poorly.

No need for a leakdown test unless you know there is low compression, a leakdown test will tell you where the compression is being lost (rings or valves), other than that it tells you no more than a compression check, maybe a bit less...

There is no reason to take the oil filler cap off when the engine is running, that is not telling you anything.

 

The oil reason I took the oil cap off after running it for about 10 mins, is that I could hear pressure coming out of it, which was new to me.

Thank you, I will ride it around a bit and see how it does.

 

Rocker box gaskets installed in the right direction? If facing the wrong way they can block the breathers.

 

Breather bolts unrestricted? You should be able top feel the crankcase pressure puff out of the breather bolts.

 

what type of ring??? some have quirks and diff break in
a major reason why you get blow by is not doing the cylinders correctly
1. coon *** way is throwing a set of rings in an old bore even though scuffed up.
2. taper is too much
3. rings installed incorrectly (i picked up a shovel for a song and a dance from a dude who installed the rings upside down and it smoked more than before the work, he was afraid and sold it)
4. IMPROPER HONE!! you will be surprised at how fast a set of rings are destroyed like a rasp on an oak board.

 

Did you use new stamped steel breathers? Were they assembled correctly?

Leaving the dipstick loose is not a good idea. The system needs to be closed for the breathers to work.

If you hear a hiss opening the dipstick, is it blowing out or sucking in?

 

All, quick update.. I found the problem, I assembled the breather incorrectly. I have since corrected the breather and now the motor is running great. Time for a tune!