Re: My first bike, a 1979 CB750L

Posted by sgtslag on May 21, 2012; 4:41pm
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/My-first-bike-a-1979-CB750L-tp4003780p4005116.html

Get yourself an impact wrench to safely (usually...) remove that drain plug.  Use a Torque Wrench, and seat it properly (28 lbs.-ft., if I remember correctly).  Get yourself a copy of the FSM from the Home Page, here; pick up a Clymer, used, for less than $10, as a supplement -- it's good, but the combination of Clymer, and the FSM, is best.

These '79K/L engines run at 250 F, two-up, at 55 MPH...  That is the thermal limit of dyno oil.  Above 250 F, they break down into carbon deposits, and sludge, inside the engine, and the transmission.  Synthetic oils will break down at 400 F.  While synthetic oils won't break down in your engine, your seals will still take a beating from the heat, drying out, becoming brittle, if your engine goes higher than 250 F.  High oil temperatures are hard on these engines.

If you plan on racing it, at all, look into adding an oil cooler (1981/2 CB650 SC Nighthawk's came OEM with an oil cooler which will bolt on, directly).  An oil cooler will keep your oil at around 210 F, no matter what, if the bike is moving.  I installed a system using a similar radiator (possibly identical, don't know) off of a CB900 Custom, with an adapter.  My oil temperature gauge shows it holds at 210 F, under all conditions where the air temperature is above 70 F (hottest ride thus far, was 90 F, with oil at 210 F, riding for 2+ hours at 60 MPH, two-up, full saddlebags, trunk, and tank bag).

I've run Shell T6 for 2+ years, no issues.  I run it in all of my engines (two cars, one truck, two motorcycles, two lawn mowers, one snowblower, and an air compressor), one oil to stock:  5W-40, ~$21/gallon at Wal-Mart.  It is available nearly everywhere.  If you need oil on the road, just get a quart of Shell T5 (if T6 is not stocked), conventional, at any gas station, and you'll be fine.  Cheers!