flitecontrol - I have to say, I've never been a big believer in reading a spark plug. My gut always told me they don't change in color quick enough to be clear enough on what's truly going on with a combustion event. Which is what led me to buying the wideband AFR for my Scamp. I had to replace the whole exhaust on that LA 360 anyway. So when I did, I bought headers, 2.5 inch pipes, ran that through a X-Pipe and Borla mufflers. I had a bung mounted on each exhaust bank. Boy, what an eye opener for me. I had been having the most difficult time cranking the Scamp prior to the new exhaust and gauge because I kept flooding it.
However, upon installing the AFR gauge, I found out quickly, that I was having a hard time starting the Scamp because … I wasn't giving it nearly enough gas! I wasn't flooding it at all! I learned that if there's one thing an LA V8 just loves, and that is GAS. I swear, it seems like I could fill the cylinders with gas and the sucker would fire right up. If it weren't for the AFR gauge, there's no telling just how --itty the car would crank and drive. And how poorly it would be carbureted. I would probably be in a constant state of aggravation with that car. An AFR gauge is a gift from God. Now the Scamp fires right up, and all except for one lean stumble off-idle, (which is a downleg booster Edelbrock trait), the car feels like it is fuel injected, and will melt the tires. That's why when I got the Rebel, I just knew I would have to put the AFR gauge on it. I had a local trustworthy shop do an alignment on the Scamp. And the tech came back and said, "there's one thing about it … that Scamp sure runs good." Had a Scamp load of friends ride with me to lunch one day and wanted to feel the power. One of them commented, "I didn't think it was going to pull like that." And the rest were all in agreement. I have learned a lot about Edelbrock carbs and tuning with an AFR gauge! Anywho…
If you were going 55 - 60 mph uphill, it stands to reason that main jet was largely involved in that. One thing I can note is that once the main jet is involved, the AFR tends to drop very linearly from the point the main jet first gets involved until the throttle is pinned. With a pinned throttle at 55 to 60 mph on the stock main (and all other stock stuff like filter and airbox), the AFRs will hit the 9 to 9.5 level (as shown on my plot). But if you weren't pinned it could have easily been 12.5 or higher … even to slightly above 14.7. There are lots of throttle inputs on the Rebel that run the AFR to a perfect condition. But what's a perfect condition? Depends on who you ask. The engine, the environment, me, you, will all have differing opinions. I like the fact that there are conditions the Rebel goes extremely lean. As long as it runs good. And I like the fact that the stock carb has the ability to completely satisfy both cylinders at max rpm and WOT. I was not expecting it, but the carburetion on the Rebel is able to quickly swing from super lean, to super rich. It can cover a lot of AFR ground.
As for why yours were so white? Dunno, never a big believer in that. Maybe your ride prior to your chop got the spark plugs really white and then your chop pull didn't change their color that quick (just speculation). I have not a clue. But one thing I can tell you, this AFR gauge doesn't lie. Will my tuning make much difference? Meh … maybe not. We've only 234 cc to work with. But any improvement in 65+ mph performance I'll take, especially if it will use a skosh less fuel in doing so.
2016 Honda Rebel 250 - The "Piglet."
AFR sensor equipped and downsized to a 0.105" main jet.
The only changes so far.
Bought on 6/29/19 with 44 miles.