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28
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10/11/2025
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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
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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.
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