Technical Q and A for classic motorcycle maintenance and repair.
Editor’s note: If you’re having trouble with that old Suzuki, BSA or BMW, Keith Fellenstein is your guy. From motorcycle tuning tips to detailed motorcycle engine repair, he can draw from a wealth of experience to help guide you to success. Send questions to: Keith’s Garage, 1503 SW 42nd St., Topeka, KS 66609, or send an e-mail with “Keith’s Garage” as the subject.
Q: I just bought my first Harley-Davidson, a 1979 Sportster, after years of owning Japanese bikes. Reading the OEM service manual about changing the oil, the manual mentions the possibility of “the oil pump losing prime because of trapped air” after draining the engine oil. “After 1 minute if the oil light doesn’t go out, loosen the oil pressure switch with engine running and let 2-oz drain from the threaded connection.” After speaking to a few Harley mechanics in the area, I’ve been told not to worry about it. I just hate the thought of the engine running for a minute without proper oil pressure, and loosening the oil pressure switch is a chore. Am I making too much of a deal over it? Will the air work its way out by itself? Is there an easier way to remove the air? How about a tee between the oil pressure switch and the oil pump with a petcock? — Ted Chris/Horn, Florida
A: I can’t claim much experience with Harleys, so I’d defer to the actual Harley mechanics and the service manual in this case. You’d be surprised at how little oil is needed to keep the plain bearings happy if the engine is not pulling a load, so even though a minute without oil pressure sounds bad, if you’re not revving the engine it’s probably not as bad in practice as it sounds. MC