Interesting unintended fix - 2002 Yamaha 225 dirt bike

OVERKILL

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A friend of ours, after saying for years he wasn't going to sell it (we had asked him about buying it many times), decided to finally get rid of his 2002 Yamaha 225 dirt bike. We had bought my middle child a Honda 80 years ago that ended up breaking and never getting fixed (sold it "as is" to a guy on FB Marketplace, simply didn't have the time or motivation to dig into it) so when the opportunity presented early last year to buy this much newer one with a well-known history, we jumped on it. I bought a 4-wheeler from him ages ago that has been a great bike (belongs to my eldest now). He gave us a good deal, and of course, in the interest of full disclosure, told us that it smoked a bit, and demonstrated by firing it up and giving it a few revs, where it behaved as described. We were fine with that, given the price, and we knew it ran well otherwise.

So, we get it home. My son eventually takes it out to his girlfriend's and they take it to their camp. He drives it quite a bit. Still smokes. Owner had been running the Canadian Tire ATV 10W-40 in it, and sent a bottle along with the bike. He goes up there for several weekends in a row, bike always smokes a bit, like we were told, but otherwise runs great and he's getting great use of it, so everybody is happy.

I send Dave from @High Performance Lubricants a message about what he'd recommend I order for the bike, wanting to switch it to HPL, and he tells me that he'd just run the Super Car 0W-40 in it, which I already have on hand. I was like "seriously, you don't think there's anything more appropriate?" He replies "nope, it'll be perfect for it". So, I give my son a few quarts and he picks up an OE filter from the dealer on his way out there for the weekend.

A couple weeks later, he's out at his GF's and he and her dad do the oil changes on his ATV and my son's dirt bike in advance of heading back up to the camp. Out comes the CT 10W-40 ATV oil, in goes the HPL Super Car 0W-40. They take the bikes back up to the camp, son drives around on the dirt bike for a while and then notices that it's no longer smoking. At all. Bike sits overnight, fires back up the next day, no smoke.

When he gets home I asked him how the bike is working and if he got around to doing the oil change yet? He tells me that yes, they did it before going up and that it is running well. Then he casually mentions that it stopped smoking after the oil change and I was like, wait, what, seriously? So he relays the above to me. I asked him "are you sure, like it doesn't just smoke less?" and he replies "no, it completely stopped". So I tell him to send me a video the next time he's out there, which he does:


I message Dave, he laughs and basically just says "that's pretty cool". We speculate a bit on what the mechanism might be that stopped the smoking, but we aren't really sure. Bike comes home for the winter and I see it with my own eyes. It doesn't smoke, even after sitting for a few months, nothing. Absolutely wild!
 
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WTH is in that oil to have such a dramatic and quick effect?
Ive never seen a transformation like that before just from an oil change. I agree, this is wild.
Yeah, it's a puzzling situation. The hilarious part is of course that this wasn't an additive/wizard, this is just oil.
 
That's great news! As always, a quality oil can prevent such problems. And as in this case, sometimes fixes them. I guess the implication here is that the oil ring was somehow stuck or contaminated and that the use of HPL was a cure.

Air cooled engines really should use a quality synthetic oil of adequate viscosity. Temps can easily get out of control. My old XR600R was much the same. It smoked when I purchased it. I took it apart and the oil ring was full of carbon. I switched to syn and re-ringed. Prob solved. Lasted for decades!
 
The only thing that I can think of is that the previous owner didn’t run it hard enough and long enough. Your son probably runs it much harder and going to GFs house often means it’s used often.

So perhaps the oil rings were already in the process of getting back to normal and a high quality oil helped to seal the deal? Pun intended 😉
That's great news! As always, a quality oil can prevent such problems. And as in this case, sometimes fixes them. I guess the implication here is that the oil ring was somehow stuck or contaminated and that the use of HPL was a cure.

Air cooled engines really should use a quality synthetic oil of adequate viscosity. Temps can easily get out of control. My old XR600R was much the same. It smoked when I purchased it. I took it apart and the oil ring was full of carbon. I switched to syn and re-ringed. Prob solved. Lasted for decades!
I plan on getting some pics of the oil filter when he does the next oil change on it, I'm curious to see if we'll have carbon, presumably liberated from the ring pack, that would indicate this being the source of the problem, and the oil removing that, the solution. If not, then I think it's back to the drawing board as to what happened.
 
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