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.
The great oil question
Q: What type and brand of oil should I use in my 1992 Honda Nighthawk? It has 15,000 miles on it. Do I have to be concerned about using a certain kind of oil for a wet clutch? — Vaughn Giddens/Northeast Texas
A: Here’s a question with no answer that pleases everyone. Every brand of oil has its cheerleaders. The only thing I will say is that for a vintage bike with a wet clutch you should stay away from modern oils with friction modifiers. They will usually be identified as those oils with a very low winter (W) weight, i.e., 0w-40. The friction modifiers will make your clutch slip. Another topic for endless discussion is the amount of zinc dialkyldithiophosphate (ZDDP) added to the oil. This additive helps lubricate high pressure contact zones like flat tappets and camshafts. Unfortunately, phosphorus is poisonous to catalytic converters, so modern oil formulations contain less than oils formulated before catalytic converters came into widespread use. If you’re stuck using an oil with low ZDDP percentage you can always use an additive. Be careful though: Too much ZDDP is almost as bad as too little. MC