1967/1969 Bonnie Rebuild Desert Sled Project

[speedrattle]

sikatri, there is one modern oil formulation that has caused problemd in the past and that is the increasing sulfur content in gear oils, which can corrode yellow metals in tbe presence of higher heat and moisture.

the older GL-4 mixes were of intermediate EP levels and *lower* concentrations of sulfur compounds. later GL-5 gear oils had much higher levels of sulfur, and corroded tje copper, brass, and bronze in older gearboxes. so tne general recommendation was to avoid GL-5.


i follow this controversy very casually and tberes lots of disagreement tbese days about whether modern GL-5s will damage old motorcycle boxes. certainly the hypoid-friendly EP additives arent necessary with the ancient straight-cut gears our stuff uses.

i think the answer here is to look at tbe label and make sure the gear oil is safe for yellow metals.

one example where a later grade is not always backwsrds-compatible

 

[Sundance]

I’m just now getting around to my T120R build again. I am going to check my valve clearances after having run the engine for about 90 miles. I see in the Clymer manual that the valve clearances for the 650 are supposed to be 0.002” (0.05mm) intake and 0.004” (0.10mm) exhaust. Then for the 750 it is supposed to be 0.008” (0.20mm) intake and 0.006” (0.15mm) exhaust. So my bike was a 650 and now has a 750 kit on it. I’m assuming that since it was originally a 650 I should use the clearances as for the 650 shown in the book? Thanks for any comments.