I've been needlessly wasting money on "91 premium" for my stock 70s Yamaha's. Thank you all for the education, I am going to do "87 regular" going forward.

Msavitt, I think markt was saying what will work, not necessarily what you should do.  One big downside to 87 octane in USA, it all has 10% ethanol, which I believe was touched on, this topic.  Also was mentioned about stability of the fuel.  If 87 sits for a while it will decrease octane.  And the ethanol will wreak havoc on your carb, if you let it sit for any prolonged period of time.  As was also mentioned about the wire on efi sleds, 10% ethanol fuel will run leaner than straight gasoline, so you might have to bump your main jet and a clip position on the needle to be safe.

Darinm, do you still got the ts185?  That was one of my first bikes, loved that thing.  I rode it everywhere, no care that it had zero license or insurance.  I also didn't have a driver's license, but oh well.  Lol.  Probably put a 1000 miles on that bike.  Rear sprocket was so shot the chain would skip, but I just kept sending it.

The only ethanol free gasoline available at gas stations near me is 87.

Markt, i've never seen that, but I don't travel much either.  We get offered 91 octane no ethanol in mn, at least what i can find.  And it specifically says on the pump for old vehicles or recreational use.  Maybe Minnesota mandates it.

Knutco11, still have the TS185, it's a great bike and surprisingly different from the Yamaha 175 of the same year. Their stock chain was just terrible, I was lucky enough to find a low milage bike and the chain was already worn out.

MarkT I feel you on that, hard to find non-ethanol anywhere in California.

Sorry Schu I missed your response. Yes as no for dependability; Much like motorcycles split into more specific categories in the 70s, snowmobile design hit a fork in the road too. A modern trail sled will typically hit 5-10k miles before needing anything major outside of standard oil changes and what not. So yes a lot better than the 70's, just like Yamahas newest trail or dual sport machines have an incredible lifespan, like the 26,000 mile valve check for the WR250R. I'd expect my '72 CT2 to be problem free for more hours than a 2024 YZ250 used in race conditions.

The "mountain" segment of snowmobiles is much like the racing segment of motorcycles, performance and low weight at the cost of longevity. On the Suzuki/Kawasaki RM100/KX100 I believe they specify something like 7 hours per piston and rings in racing conditions, and for trail riding people push them quite a bit further, yet nothing like a dedicated dual sport or trail bike. Thankfully snowmobiles aren't quite that bad, though 2000-3000 miles is pretty standard timing to do a top end. What gets you are the other wear items, clutching could be yearly and is expensive, the drive chains are prone to breaking and some companies are posturing that the track, at $2,000, is a "wear item". Plus all those hidden nasty things under the snow like rocks and tree stumps really take a toll on suspension components if contact is made. Perhaps the most painful part is that a 2024 YZ250 is $8,199 and a 2024 high end mountain segment snowmobile is over $20,000, and all the dealers really gouge you on the parts, think BMW style, for example Arctic Cat thinks their fuel pump assembly is worth $563, while Yamaha "only" wants $350 for a WR250R fuel pump assembly. Either are out of what I want to spend on a machine for fun anyhow, so it makes me learn how to repair more problems with used parts

Knutco11 thank you for your thoughts, they make sense.
I am in CA and do not recall seeing a "10% ethanol" tag on the pump which I was very accustomed to seeing in IL and the corn belt before I migrated to CA, so I assumed (perhaps incorrectly) that the 87 had no ethanol blended in.

are gas stations in CA obliged to post signage if gas includes ethanol?

by the way, as a fan of pork products I abhor ethanol in gas because it drives up the price of same!!!

I'm pretty sure that all gas sold at CA stations has 10% ethanol. A neighbor buys 93 octane ethanol-free gas cans at Home Depot for his vintage bikes, but it's expensive. $24 for 110 ounces (less than a gallon), but he doesn't put many miles on them. I just use 91 octane from the gas stations.

Yes, very hard to find ethanol free in the west.  Near me there is only one station (brand new Smith's grocery location) and they don't always have it.