Correct Combustion? Your Thoughts
Grand HDF Member
Joined: Sep 2022
Posts: 4,418
Likes: 3,823
From: Florida
Just friendly banter Tom Tom.. gotta read the room. CV carbs have a great reputation and check the box. I was only saying my team is better than your team with a smirk of jest. The green smiley guy was the clue!
Last edited by Rains2much; Apr 8, 2026 at 05:51 AM.
Seasoned HDF Member
Joined: Jul 2014
Posts: 8,590
Likes: 3,361
From: Cental, MI
Even our Race gas shows more color than that... is it Methanol??
Last edited by t150vej; Apr 8, 2026 at 11:43 AM.
Grand HDF Member
Joined: Sep 2022
Posts: 4,418
Likes: 3,823
From: Florida
here’s some from my Softail.
the pics I previously posted I grabbed from the internet to show an exaggerated line to convey the timing mark. It’s harder to see from a pic of my personal plugs from this post
Last edited by Rains2much; Apr 8, 2026 at 12:45 PM.
Intermediate
Joined: Nov 2025
Posts: 36
Likes: 13
From: florida
Does different octanes cause different plug reads? If Im running 90, which I do, does 87 or 84 have a different read? Higher octane means a hotter burn which would look like a lean condition. Am I miss understanding this? Thanks
HD Forum Stories
The Best of Harley-Davidson for Lifelong Riders
7 Surprising Harley-Davidson Products that Are Not Motorcycles
Verdad Gallardo
8 Best Harley-Davidson Motorcycles Ever
Pouria Savadkouei
10 Worst Harley-Davidson Motorcycles Ever
Pouria Savadkouei
Killer Custom's Jail Break Is The Breakout That Refused to Blend In
Verdad Gallardo
Crazy Bunderbike Build Looks Amazing, But Is It Impossible to Ride?
Verdad Gallardo
Harley-Davidson Reveals Super Cool Cafe Racer Concept
Verdad Gallardo
Engraved Rebellion: Inside Bundnerbike's Glam Rock II
Verdad Gallardo
10 Motorcycles You Should Never Buy
Joe Kucinski
10 Things Harley-Davidson Needs to Fix in 2026
Verdad Gallardo
Grand HDF Member
Joined: Sep 2022
Posts: 4,418
Likes: 3,823
From: Florida
High octang does not cause your combustion chamber to burn more hot. It does not cause by itself for you to make more power.. it’s actually the opposite. What high octang does is detonate at a higher temperature. What that means is when you run high compression, you can run more timing to make the power that should be there with high compression without the detonation. The lowest octane that allows you to run the highest advance timing usually makes the most power.
When guys start pulling timing out, it’s because the compression is high and they want to make sure it does not detonate. They start going backwards from just having lower compression and running more advance timing. Everything is compromises and trade-offs. In Ohio in the late 90s almost every gas station had at least one pump of 100 or even 110 octane gas and it was ethanol free. Those are the glory days lol.
‘’Back in the day my shovel would run on turbo blue the 110 stuff, my plugs would be grey, almost no sign of any tan. But it was right. The timing and tune were on, the mph and no ping would prove that to me. Street gas of 93 is kinda going that way. Old better ethanol free gas was the traditional tan.
Last edited by Rains2much; Apr 8, 2026 at 02:44 PM.
Seasoned HDF Member
Joined: Jul 2014
Posts: 8,590
Likes: 3,361
From: Cental, MI
Note; ethanol is Much Higher Octane Rating than Gasoline...so... Stands to Reason, more Alkyhol in yer gas = Higher Octane..Exactly the opposite of More Power, or Hotter!!
All Octane does, is resist burn...ie, Resist Pre-ignition...Spark Knock!!!
All Octane does, is resist burn...ie, Resist Pre-ignition...Spark Knock!!!
