Board index Flathead Power-Technical Questions, Answers, and Suggestions Big Twin Flatties Wet-Sumping revisited.

Wet-Sumping revisited.

Moderators: Curt!, Pa

Post Sun Jan 12, 2014 9:45 pm

Posts: 470
Location: Six miles East of Cheney, Wa.
Just a thought. I pulled the cap off the one check valve towards the rear of the bike, on my oil pump, and it just didn't look like the cap could be putting much pressure on the spring....the spring sure seemed to be a bit short to my eyes. I know that there isn't supposed to be much pressure on that a pound and a half or so, but still.....

So, I stretched the spring a bit, just enough that I'm sure it's being compressed when the cap is on/tight, and not just bouncing around in there, short of being compressed.

Since I'll be starting and running the bike on a regular basis now, I don't think I'll know if it's still wet-sumping or not...won't know if that made a difference. Took about two months last time. But I'm just wondering how many bikes wet-sump because the check ball spring is too short, or has lost tension. ???

Once again...just a thought!


Post Wed Jan 22, 2014 1:19 pm

Posts: 150
Location: Carver, MN

Let's see, a 60+ year old spring loose some tension, what are the chances? Stretching it may be a reasonable stop gap measure, but for a spring that retails for about a buck you might consider treating your ride to a new one. :D

Post Wed Jan 22, 2014 7:22 pm

Posts: 470
Location: Six miles East of Cheney, Wa.
I won't consider...I'll just do it! It's funny that the person who rebuilt it, didn't put a new one in...or maybe it is new. We'll never know.

Now I read somewhere that that check valve, the one furthest back, to the rear of the pump, is sometimes disabled. ? (purposely) No, I wouldn't consider doing that, but did hear that somewhere. Something to do with bleeding off pressure at low rpm. ? Or not.



Post Thu Jan 23, 2014 6:40 pm

Posts: 1642
Location: Interlaken, NY USA

No, you wouldn't want to disable any of the check valves, but on the later larger pump with the centrifugal bypass valve, the bypass feature is sometimes disabled. That's done by blocking off the passage at the gasket surface. These motors really don't need to bleed off oil at low speeds directly to the cam case. That's a holdover to the days before effective oi rings were used.

Post Thu Jan 23, 2014 7:07 pm

Posts: 2677
Location: Los Angeles, CA
Stretching the spring can cause more damage than good. It could make it take too much pressure to open creating a loss of oil.

Post Thu Jan 23, 2014 8:03 pm

Posts: 470
Location: Six miles East of Cheney, Wa.
That's possible, but I didn't stretch it much, just enough to make sure it was under tension. It looked to me like it was possible that it was short.


Post Fri Jan 24, 2014 7:43 am

Posts: 1605
What's the cost of a new spring?
Shoot, a man could have a good weekend in Dallas with all that stuff...

Post Fri Jan 24, 2014 9:48 am

Posts: 1642
Location: Interlaken, NY USA

I wouldn't worry about stretching the spring, if follows directly after the pump output, which can easily reach 25 psi. The ball WILL open. The low pressure readings normally seen on a hot bike are the hot oil pissin' away through roller bearings, loose seal at cam cover, etc. That pump will open the ball valve, after that, well, the story doesn't change.
Of course, I'm sure a new spring is cheap, suit yourself. :-)

Post Sat Jan 25, 2014 11:13 pm

Posts: 1605
I'd replace a small, essential part like that as a matter if course, never out the old one back in
Shoot, a man could have a good weekend in Dallas with all that stuff...

Post Tue Feb 25, 2014 10:37 pm

Posts: 32
My WL is a wet sumping nightmare!!!!! Within one week I end up with oil all over the floor. To date I have done the following
Replaced the Springs
Replaced the Balls
Replaced the balls again but this time with whizz bang rubber ones from Germany
Purchased and used a Burnishing tool

and it still wet sumps!!!!!!

I need to either buy a new pump or put a tap in the line

Post Wed Mar 05, 2014 7:16 pm

Posts: 470
Location: Six miles East of Cheney, Wa.
Strange as it may seem....Due to circumstances beyond my control, up until today, I hadn't started up the Little Mistress since January 26. That day, after running it a bit, I stretched that spring, and changed the oil to straight 50wt. Or I might have done that before that, but the 26th was the last time it ran.

For the engine's first few start ups (fresh rebuilt engine) I had some light oil in it. Some 10-40 I believe, or something like that. It was wet sumping like crazy.

After sitting for over a month, fired her up today and it hadn't wet-sumped at all. The only variables were stretching the spring, and changing to a heavy oil.

I tend to think that the spring, and therefore the ball, was not under any pressure. I think the spring was short. It looked short. The heavier oil might have played a part, but over a month should have been enough time for even it to slip past the ball. ??? But I really don't know.

Something to think about.


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