Recommended fuel for a '80 cb750

[Whats_up_DOHC]

Hi everyone, quick question here, what is the recommended fuel type for a '80 cb750?

I looked up in my Haynes manual as well as the original honda manual but couldn't find any information concerning fuel.

I usually fill it up with ordinary gas, but I heard people say that high octane fuel is more appropriate for this engine.
What do you think?

 

[dirtdigger]

premium fuel is not required for these. They are only in the 9:1 compression ratio range. 89 octane range is our middle grade around here. I would not go with anything lower than a mid grade fuel.

 

[cafeken]

i run 93 in all my bike's

 

[dirtdigger]

You of course can run higher octane but it is not necessary in the sohc or dohc motors. The compression is low enough on the stock motors not to warrant the premium fuel but it wont hurt anything obviously.

 

[Whats_up_DOHC]

All right folks, thanks for the info

Cya!

 

[Sterbo]

I've heard from most people that the ethanol infused crap is harmful to these motors. Carbs, lines, tank... TRUE or FALSE? I try and find stations where there is 100% gasoline because running fuel that was around when these bikes were built is best. minus lead. Thoughts?

 

[Whats_up_DOHC]

Good question, fuel at most gas station can contain up to 10% ethanol, if it is harmful for the bike then we're screwed!

 

[dirtdigger]

We have to contend with ethanol around here too. In small amounts you will never know the difference. The problem with ethanol is it is an alcohol. It absorbs moisture and is corrosive to plain metal. You also get less power from the same amount of ethanol as you do with straight gasoline and it tends to run leaner with the same jetting. When I was an auto tech I did see issues from ethanol. Corroded fuel tanks and fuel rails, fuel pump failures, vapor locking. GM actually had to update there intake gasket material on the newer motors to cure a gasket failure on E85 vehicles. Generally you are safe with up to 10% but no higher...and I wouldn't leave it in the gas tank or in the carb float bowls for extended periods of time.