What octane should I be using?

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billsoll · #1 Unread post by **billsoll** » Tue Apr 05, 2005 3:58 pm

I have a 1981 Honda CB750K with 9.0:1 compression ratio. I can't find any info telling me what octane gas to use. Can anyone tell me?

#2 Unread post by **Skier** » Tue Apr 05, 2005 4:19 pm

Well, you manual should tell you. If not, there is probably a sticker under the seat that tells you all kinds of good information like required octane as well as spark plug type/gapping, timing, etc...

Failing those two, you can either head to the internet and search or do this:

Ride your bike until you hit reserve. Drop in a gallon of medium grade gas (89 octane in my area). Ride the bike around a bit and listen for detonation or pinging. It'll sound like gravel being ground up in your engine. If this happens, lightly ride your bike to the gas station and fill the rest of your tank with premium - you'll need to use premium in it. If the bike doesn't ping or knock, you can run that gallon until you hit reserve and try putting in a gallon of the cheap stuff (87 octane, here). If THAT knocks or pings, fill up with the mid grade and you can use that.

Clear as mud. I just throw in premium (91) in my bike, since it's air cooled and can get real toasty.

oldnslo · #3 Unread post by **oldnslo** » Tue Apr 05, 2005 4:29 pm

Regular should work fine. Mine has about the same comp ratio and is happy with reg. Premium fuel is a waste of money if your bike is tuned for regular. I have heard all the stories about cooler burning, more even burning, blah, blah, blah, but in the end, if it works well with the cheap stuff, then use the cheap stuff. There is no status included in premium fuel, and your bike won't go faster or last longer if you use it.

billsoll · #4 Unread post by **billsoll** » Wed Apr 06, 2005 1:08 am

Thanx for the input. I'll look under the seat today. If I don't find anything, i'll try the 1 gallon sequence starting with 89 octane.