Oil Cap blowing off

[Bmarchant]

Hey Guys,
I've read the threads on this, but some of the information (photos) is missing.
http://www.bigdogbiker.com/forums/help-wanted/15306-oil-cap-blowing-off-2.html

My 2003 Chopper started blowing the oil cap off. RAYWOOD had a photo of a vent hose to check, but the photo is now missing. I noticed he said the tank is vented. Can't find where?

The fittings on the top of the manifold and carb are for the head venting used on twin cams and the 05 and new BD's. Your 04 should have the breathers on the two mounting bolts on each head. I would check these to see if they are clogged or if they are not venting if they are still run to the carb backing plate. Still doesn't make sense as the tank is vented so trace the vented oil line and see if it's pinched or pluges. It exits out the bottom of the tank and flows into the motor on the side of the oil pump.
I have a picture of the hose routing somewhere in my gallery.





Here it is, you have pressure building up in your motor somewhere and it's probably the vent line (B) is plugged:

Anybody know what hose Ray was pointing to? Or where the vent to the tank is? (oil tank, I'm guessing).

Thanks,

Bmarchant

UPDATE: My oil cap was very loose. You could just lift it off with no effort at all. So I bought a HD oil cap with a temp gauge, and its now staying on. I've gone out twice now and got on it, came back and its fine. Its also fixed the noise I was hearing from my engine last week where it sounded like a whistling sound was coming from my engine.

My guess is, the whistling sound was the pressure leaking through the oil cap with it that loose. Sounds like these bike run under a slight pressure in the oil system.

 

[NYchopper]

What is the part number for the Harley oil cap? Mine has popped off a couple of times. They don't fit real tight. Thanks.

 

[tommy666]

Check behind your air cleaner too. Something as simple as a gasket/o-ring out of alignment will cause the crank-case to build pressure....Happened to me twice on my harley.

 

[Bmarchant]

Check behind your air cleaner too. Something as simple as a gasket/o-ring out of alignment will cause the crank-case to build pressure....Happened to me twice on my harley.

Excellent, didn't know that one.

I've got the Harley part number at home, I'll post it tonight. Works great.

 

[Kdub]

Check behind your air cleaner too. Something as simple as a gasket/o-ring out of alignment will cause the crank-case to build pressure....Happened to me twice on my harley.

What happened when the crank built pressure?

 

[tommy666]

Oil cap blows off or something even worse.

 

[Kdub]

Hmm my buddies bike lost top end power and started blowing oil out of somewhere. Wonder if this may be the case.

 

[tommy666]

could be. I just competed the 95" build and was out on a maiden voyage. Needless to say, hot oil squirting up your pants leg @ 110 mph doesn't feel good.

 

[Kdub]

Hmm. His oil cap was still on but I think it was threaded. I'll have to take another look. Thanks for the info.

 

[silver09]

Crankcase pressure will cause alot of different issues i deal with that alot on turbocharged cars the main problem is oil leaks . Make sure it can get rid of the pressure.