Board index Flathead Power-Technical Questions, Answers, and Suggestions Shovels Breather purging

Breather purging

Post Sat Jun 09, 2007 4:19 am

Posts: 43
Location: Plymouth,Ma. USA
I have a 1980 fl that is puking large amounts of oil from breather hose that originally went to air cleaner but has since been rerouted under bike.
I checked the oil pump for sheared keys and found none.
I checked oil lines and all seem correct.
I freshened up oil pump and still have the same problem.
Scratching my head on this one.
Any thoughts??

Post Sat Jun 09, 2007 8:29 am

Posts: 32
Location: Oklahoma City OK USA
does it puke every time? Or just if it sits a couple days or longer? If only when it sits, you may need a new checkball & spring in the oil pump. The
ball's job is to hold the oil in the tank against gravity flow. The pressure
when it's running pushes it up. It may have corrosion or flat spots. If the
ball is bad, the seat it fits into may be bad also. There are ways to repair
that on this and other forums. One member has even built a tool to make this repair professionally.
If it sprays oil the whole time it is running, your chain oiler may be open.
Or if your engine is made from parts of different vintages (as my new Pan
is) there may be a passage from the oil pump into the cam chest that is
putting so much oil into the lower end your scavenge side can not keep up. Have you removed the return line & started the engine to see how the
return flow is? On a stock '80 you can remove the large cap under the seat, and see the flow. Caution, you may get oil everywhere! Pull the filter
out to perform this. Put the bike on a stand or table to sit level. Pull the cap then start it and watch. Probably get a new gasket for the cap if it's been a while since the cap was off.
Good Luck, I'm still chasing mine, too. d.rinner-okc
old harley parts are MY 401K!

Post Sat Jun 09, 2007 2:58 pm

Posts: 54
Location: NYC / NoHi, CT
check check ball and spring

no I didn't stutter.

as d.rinner intimated, your check ball may be hanging up.

hope this helps.

let us know.


Post Sun Jun 10, 2007 3:02 am

Posts: 43
Location: Plymouth,Ma. USA
Check Ball is OK
Doesn't puke at start up like when oil seeps to lower end. It has to run for 2~3 minutes and then it starts to flow out breather. As I said before keys in oil pump are good.
Bike does have a home made oil tank . Possibly vent tube is too low???

Post Tue Jun 12, 2007 10:35 pm

Posts: 1050
Location: Greenbackville, Virginia, USA
Does it still have the stock plastic breather gear? If so, replace it with a properly fitting metal breather gear. Those plastic breathers were one of the factory's attempts at saving money and are a P.O.S. G

Post Wed Jul 16, 2008 11:20 pm

Posts: 1538
You posted: "Possibly vent tube is too low???"
Maybe you could lower the oil level & re-test, Of course keeping it still at a safe level tho...
Last edited by sleeper on Wed Jul 16, 2008 11:23 pm, edited 1 time in total.

Post Wed Jul 16, 2008 11:22 pm

Posts: 1538

Post Sun Aug 03, 2008 3:28 am

Posts: 43
Location: Plymouth,Ma. USA
The problem with purging was found to be the oil tank which had been modified.Not sure what was wrong exactly because the tank needs to be cut open to inspect the tubes, Put stock tank back in and have no more problem.This bike sat on the backburner since last year but I wanted to post reply about what remedied the problem.
Thanx for the help

Post Sun Aug 03, 2008 8:46 am
Pa Site Admin

Posts: 5839
Location: Ohio USA

Aftermarket 45 tanks had a tube issue too. There are some cut open pics in the data base of those. Pa

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