Board index Flathead Power-Technical Questions, Answers, and Suggestions Knuckles Oil tank draining down

Oil tank draining down

Post Mon Jul 02, 2012 10:55 am

Posts: 16
Is the Oil tank draining down a normal thing on these Knuckleheads? will it lose prime on the pump when all the oil is in the crank case? this happens in about a week of setting :shock:
EL Roccky

Post Mon Jul 02, 2012 11:27 am

Posts: 391
Virtually all of them will sump at some point, but a week is on the extreme end. Many will do it if left unridden for a long period, most ridden regularly do not do it at all! So it is not normal. Sounds like time to check the seats in the pump and replace the check balls.

Post Mon Jul 02, 2012 4:53 pm

Posts: 16
I just had this motor put together by a shop that specializes in Knuckleheads, and they had to replace one gear in the pump, Maybe they did not do everything they shoud have to the pump, this motor had been sitting almost 60 years.
Thanks EL Rocky

Post Tue Jul 03, 2012 11:49 am

Posts: 152
Location: Carver, MN

And while you are inspecting the check ball and seat, don't forget the check ball spring. There is always a possibility that it is over 70 years old and has lost much of its tension.

Post Tue Jul 03, 2012 4:48 pm

Posts: 16
Thanks guys, should the spring be stretched a bit to give more tension? and yes this is the original 1936 spring, this motor even had standard .250" rollers in the mains and crank pin :o

Post Tue Jul 03, 2012 7:48 pm
Pa Site Admin

Posts: 5843
Location: Ohio USA

I would not suggest stretching the spring in order to gain tension. It will only collaspe again because spring tension is tempered in when the spring is freshly manufactured. Most spring steel is manufactured in long length and then cut to standard lengths per application.

Post Tue Jul 03, 2012 10:30 pm

Posts: 16
10-4, I will just get new manufactured springs, kinda like valve springs, old is old :lol:

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