transmission fluid?

Motor Oil, 10 W 40. Says so on the dipstick/fill port.

You could use 20 W 50, but it's not really needed.

Your transmission is lubricated with your engine oil, as they share the same case.

There is no "Transmission Fluid" on the older Honda air cooled engines except possibly the 400/450 and 750 automatics.

The engine is a wet sump oil bath and uses the same oil to lubricate the transmission. Tranny fluid mixed with oil will thin it out. Summers here, so unless you live in Alaska, change your oil to 20w-50 for better lubrication under hotter conditions.

Your motorcycle (CB650 Custom, 4 cylinder) doesn't have seperate engine and transmission fluid reservoirs. They are housed within the same cases and share the same oil. In most cases, you should use 10W-40 multigrade type SF or SG. Depending on where and how you ride, you might use 10W-30 (moderate temps) or 10W-50 multigrade (desert-like temps).

Your motorcycle uses engine oil to lube the trans. It is a single case set-up, possibly w/2 drain plugs, I can't remember, it's been years since I worked on 1. Read your owners manual & invest in a Clymer or Haynes manual. But MOTOR OIL ONLY.

PS: When in doubt go to a Honda dealer, not an auto-parts store.

Former Honda MC Tech

Use 10w 30 i have found that it is the best in the hondas. DO NOT USE ANY TRANSMISSION FLUID.

Use 10w-40 and change frequently.

dextron 1 or 2