I've only been able to find 87 octane ethanol free fuel where I live. I want to stick with ethanol free fuel so, is 87 octane good enough to prevent detonation during hot weather riding? Or should I add and octane booster chemical?
Should be fine stock compression is only 9.5:1 depending if you have the timing mod or nor.
For storage I run 87 ethanol free (clear) gas in my 1380 with 10.5-1 compression. It runs fine for short around town warm up rides. Long rides, hot weather I run 91 E10 gas, no problem....the E10 only plays havoc when I store my bike....I then drain the tank and go back to 87 clear gas if the bike sits for 2 weeks or more.
With a stock FJ, the owners manual specifies using regular 87 gas. You should be fine.
Stock FJ factory jetting runs lean, when you get a chance remove the #37.5 pilot jets and put in #40 or #42.5 pilot jets and bump your mains from #110 to 115 or 117.5.
Your bike will run cooler in the hot summer thin air high altitude Colorado locales.
Cheers
Pat
Hi Pat,
After I bought the bike last spring I overhauled the carbs and installed a dynojet stage 3 Kit with 120 main jets and 144 pilot jets then tuned the carbs accordingly. Bike runs good as far as I can tell but don't have anything to compare it to. I havent checked plug color yet...
Would you suggest reverting to your recommendations?
Regarding octane I was running 91 on hot days and never had any pinging and wasnt sure if E free 87 was ok.
Hey John, Dynojet has their own proprietary jet sizes so disregard my Mikuni jet sizes.
I thought you had stock jetting. I think your Dynojet jetting should be fine.
Storing your bike with 87 octane ethanol free gas is fine. Short rides are fine.
On a hot summer day @ 5,500' the air density in Lakewood is low, meaning air flow for our engine cooling cooling is less, so in my opinion, I would avoid riding in summer stop and go traffic with 87 octane gas. Perhaps I'm being overly cautious.
Other folks can chime in....
If you want to do a plug reading, be sure to disconnect and cap off, the vacuum advance, pop in fresh plugs then ride to get the plugs to the proper color.
With the vacuum advance connected, you will find your plugs are white.... not an accurate color reading.
More info on the vacuum advance: https://fjowners.com/index.php?topic=11690.0
Cheers Pat
I never had any issue running 87, or even 85 octane in my 1200.
I rarely ever ran 91 in it. Never noticed any difference in the way it ran with regular fuel or higher octane fuel, even in the summertime.
5600-feet here in Aurora.
Compression is a bunch lower at altitude, so you can run lower octane fuels. :good2:
I always stored it with "Ethanol-Free" fuel though........Makes a difference.
Thanks Alan!