Posts
35
Joined
10/11/2025
Location
WEST MEMPHIS, AR
US
So I just bought this 2024 Yz250 with 28 hours. The previous owner was running 100LL with Castor 927 40:1 with stock jetting with the only mod being a Pro Circuit 304 Slip On. I drained the gas and filled the tank with Honda HP2 32:1 with 93 ethanol free pump gas. I don't have a picture of the spark plug before the switch but it was dry and black before the switch. It's went from black to a brown color with this being the same plug. I plan on changing the plug the next time I ride. I've also noticed that the bike is dripping from the powervalve vent hose. It that due to the detergent and additives in the synthetic oil cleaning the oil deposits from Castor 027 in the powervalve?
Heat range looks good, but mixture slightly rich...
What part of the plug makes you say that the mixture is slightly rich? The bike only has about 1.5 hours of runtime on the new mixture. I’m wondering if my plug will look a lot better once I replace it.
The electrode looks good, but the flat surface looks rich, a new plug will give a better read.
How the bike is ridden also makes a difference.
HP2 created a lot of splooge in my experience
The Shop
Luxon 4-Post Bar Mounts
$189.95 - $239.95
Free shipping: VITALMX
DeCal Works Huge Plastic Inventory of UFO and Polisport kits.
Weird, I've had the opposite experience. The previous owner of my Cr250 was running K2 40:1 switched to HP2 32:1, and it eliminated the spooge problem I was having with my Cr250. It might have also been something to do with the bike being jetted for 32:1 but he was running a 40:1 ratio. Last two bikes I've owned the previous owners both ran 40:1 on bikes jetted for 32:1.
It's more than likely related to jetting, but I just wanted to throw it out there if you have continued issues with splooge.
This was after a new spark plug was installing with about 2 minutes of idling time warm up then 10-15 seconds of WOT. I was expecting more color did I do something wrong?
Rode it a little bit more
Plug looks OK.
How does run?
Runs good I heard that they run rich stock, but I think in my case it’s jetted pretty good for my elevation and everything.
This is the spark after about 20-30 minutes more of runtime with 75%-90% of being on the pipe. I think the spark looks good, but I will say the the insulator tip looks more brown in person compared to the pictures which I think was because of the lighting.
The electrode looks good, if you see carbon buildup on the flat surface, you may be able to go slightly leaner.
I switched to a 175 main and a 48 pilot. I like the throttle response off the bottom more, but almost felt like the bike had less top end, think it was just loaded up at first or I was afraid to stay on the pipe with the leaner jetting at first. I accidently put 2.183 gallons instead of 2 gallons at the pump when filling up my jug. I mixed my usual 8 ounces so I'm closer to a 36:1 ratio instead of my usual 32:1. Call me cheap but didn't want to waste $15 dollars of premix. Bike definitely feels like it![]()
revs faster with the leaner jetting. I wished I was running 32:1 but when I run this tank out I'll have a better picture of the leaner jetting. ![]()
That's looking good!
Concentrate on the throttle response and throttle position, especially in corners, where the throttle is partially open, to adjust the needle...
2.183 gal with 8oz of oil is 34.9 to 1 ratio. That's basically as close to 32:1 as likely any measuring error in the meniscus of the oil when you try to measure the 8 oz.. LOL to get any more precise than this you better start considering temperature effect and barometric pressure on the viscosity of the liquids at time of mixing.. hahaa In other words, any difference you feel when you go back to a "perfect" 32:1 is probably placebo or more related to the weather difference or amount of dirt on your air filter that day.
Clown in pajamas and slippers. Don't you know there's a dress code? Get some boots on your feet and dirt on your hands, son!
Or go back to your fuel injected KTM 125, haha
They are actually steel toe 😆Can't say I've ever own a KTM let alone a fuel injected one.
Pit Row
That's good to hear I was worried it might lean it out too much
Was the flat surface of the spark plug showing no color before because it was a tad to rich?
The flat surface from your original plug was black, indicating it was rich, this can also occur if the engine is cold (excessive idling, not running in power band)...
The flat surface from your new plug looks better...
This is the plug I was talking about
About 1.5 hours on the new jetting with 32:1 premix
Post a reply to: How Does My Spark Plug Look?