Topic: CB750K Transmission Oil Change

[David Beecham]

I recently purchased a '74 CB750K. Bike starts, runs, shifts and drives fine. Along with some other maintenance items, I want to change the transmission oil. Is that a recommended maintenance item? I ask because transmission oil change is not covered in my SHOP MANUAL. How do you drain and refill the transmission oil?

[Flyin900]

Oh boy.

Your oil in the motor is the only oil the bikes uses. It lubricates all internal components such as the wet clutch, transmission and motor.
Since you have the shop manual spend time reading over the general areas covered for regular maintenance.

[Stev-o]

Hey David...welcome to the forum.  Click here for the info you asked about. 
Nearly everything you wonder about can be found on the website!

http://www.sohc4.com/tech/cb750-faq/

The real question should be what is the best oil to use?!

[David Beecham]

Thanks for the link. Good stuff. The previous owner told me that the trans oil was separate....

For oil I generally use Rotella 15-40 or Castrol Semi Synthetic 20-50, both are JASO MA2. Any reason not to use the Castrol?

[Stev-o]

Thanks for the link. Good stuff. The previous owner told me that the trans oil was separate....

For oil I generally use Rotella 15-40 or Castrol Semi Synthetic 20-50, both are JASO MA2. Any reason not to use the Castrol?

Never believe a seller!   

I use Rotella and avoid synthetic since this has a wet clutch [could cause slipping] and minor weeping at gaskets.

Can you post a pic of your bike?

[newday777]

Thanks for the link. Good stuff. The previous owner told me that the trans oil was separate....

For oil I generally use Rotella 15-40 or Castrol Semi Synthetic 20-50, both are JASO MA2. Any reason not to use the Castrol?

Welcome aboard David and to the 750.
The Rotella will run fine in your 750 if you aren't riding it hard and fast in high heat.
I generally run 20w50 Honda oil in the heat of summer and cooler temps run the Rotella for easier start ups.

[David Beecham]

Pic attached

[grcamna2]

Welcome to the forum David.That's a Very beautiful CB750 !  Do you know if that bike has been restored once? or is original,a 'Survivor'? I run the Rotella T4 15/40 myself year-round,works good for me.

[Kevnz]

That is one very nice looking bike. Love that colour, 1974 only, I believe.

[disco]

Love the funky purple colour. We never got that one here in Australia. Very nice looking machine.

[newday777]

Pic attached

Great looking in Boss Maroon. (Funky purple in AU!)
And yes 1 year only color.
I have the 75 1 year Planet Blue(in the USA market.... European markets had Planet Blue with small stripe on the K2 available)

[74CB750K4]

Definitely a nice one!! My dad ordered one in that color in 1974 and could never get one and stumbled upon the flake orange instead and took what he could get since they were so popular.

[Stev-o]

Pic attached

Great looking bike!  [my K4 was originally Boss Maroon]

Where did you find it?

[TwoTired]

My 74 CB550 was Boss Maroon when I got it.  It's brown now, as the sun bleached out all the red pigment.

Cheers,

[Mantree]

I can conferm that the transmition and engine share the same oil.

[PeWe]

About oil for CB750
Make a Google search like
sohc forums + Spectro

Several hits on that.
Example:
http://forums.sohc4.net/index.php?topic=119643.msg1754367#msg1754367

About synthetic. My K6 use synthetic of good brand, Redline 20W-50. No clutch problem due to the oil despite 90-100whp.
 
A stock engine has less need of that kind of oil.

Using car oil one way to get clutch slip with anti friction additives car oils have.

Motorcycle oil for wet clutch the safe card.

Spectro 20W-50 mineral recommended on this forum. One member (ofreen)  has a very longed lived bike without restore on that oil. That's why I tried it after reading the zinc values as well.

You will feel when using an OK oil.
Find neutral when hot engine is standing still idling.

About zinc additives. Some are made for cars and have anti friction stuff in it too.

[70CB750]

Pic attached

Welcome!   Great looking bike.

[MauiK3]

Very nice bike.
Try to find a good shop manual, it will really help you.