Proper oil weight for motorcycle

Messages
488
Location
Ohio
I have recently bought myself two motorcycles and I am sick of paying outrageous prices for oil changes at the shop and have a few questions before I get started DIY. First bike is a 1980 Kawasaki KZ 1000 ltd which is air cooled. The clymer manual states proper oil weight anywhere from 10w40 to 20w50. (currently being run on over priced 20w50 motorcycle oil) What are the pros and cons of using each weight? I live in Ohio so I'm not dealing with any wicked high temperatures. Right now I'm looking at Delvac 15w40, but a little voice in my head says that might be a bit too thin. Second bike is a 1984 honda magna 700cc liquid cooled. Sticker on bike says to use 10w40, but was wondering if I could use 15w40 delvac without hurting her. She has 45k on her already. Appreciate in advance all help and insight.
 
Messages
12,385
Location
Northern CA
Both bikes will thrive on 15W-40 HDEO If the mfr says 10W-40 is OK, 15W-40 HDEO is an improvement. That is assuming you aren't doing a lot of riding with the starting engine temp below about 15F.
 
Messages
4,009
Location
Calgary Canada
 Originally Posted By: XS650
Both bikes will thrive on 15W-40 HDEO If the mfr says 10W-40 is OK, 15W-40 HDEO is an improvement. That is assuming you aren't doing a lot of riding with the stating engine temp below about 15F.
+1
 
Messages
6,388
Location
Washington St.
It is likely that your owner's manual gives a list of acceptable oil viscosities and the temperatures they can be used at. You can probably find where someone has uploaded pdf files of the owner's manual for each bike and you can view those oil lists. In any case, 15W-40 HDEO is a huge improvement over 10W-40 which always was a poor oil. I don't know why the Japanese motorcycle makers like 10W-40 so much, but I always avoid automobile 10W-40 and avoid any oil that has a price like motorcycle-labeled 10W-40. Use the 15W-40 or syn 5W-40, or in very hot weather use 20W-50 or syn xW-50, especially for an air cooled engine.
 
Messages
179
Location
Phoenix AZ
For any older Japanese Bike where clearances we pretty "big" by todays standards I would use 20w 50 year round ...I dont think u want to ride in 25 degree weather. I had a 77 KZ 650 That I rode to 45k before I was hit on it...got a solid diet of Castrol 20w 50...all there was back then
 
Messages
1,357
Location
California, USA
We currently use Shell Rotella T syn 5W-40 in Japanese bikes. When Delo 400 was reformulated with Moly, we started getting a bit of clutch slippage.
 
Messages
6,388
Location
Washington St.
My motorcycle mechanic works on all makes of bikes and says that the only oil he's seen that is sure to cause wet clutch slippage is Castrol Syntec. I agree with the use of any 5W-40 or 15W-40 dual-rated CJ-4/SM diesel engine oil. Or, use a 20W-50 that is either labeled for motorcycles or not proscribed for motorcycles. For example, Mobil 20W-50 "racing" oil is listed on its data sheet as not suitable for wet clutches. I prefer the xW-50 oils for air cooled engines. I also prefer a synthetic 50 wt. for the air cooled engines if they get very hot, either very hard, hot, heavy runs or lots of idling time with poor airflow. My air cooled Suzuki calls for Suzuki-branded 10W-40 oil, but also allows 20W-50 for temperatures from +14°F up, and 15W-40 from +4°F and up over 104°F. It runs great on Schaeffer #705 syn-blend 20W-50.
 
Messages
197
Location
Hartford, Ohio
 Originally Posted By: Ken2
My air cooled Suzuki calls for Suzuki-branded 10W-40 oil, but also allows 20W-50 for temperatures from +14°F up, and 15W-40 from +4°F and up over 104°F.It runs great on Schaeffer #705 syn-blend 20W-50
+1 on the Schaeffer #705. Our Harleys thrive on it too. (;
 
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