Yeah, I should know better than the leave it on. It was dripping slowly out the overflow so I was crossing my fingers it wasn't totally flooded. My lawn tractor floods bad if you leave the fuel on. Guess I will need to tip it over (already did that cause the throttle grip just slid off the bike, apparently someone put them on with grease and sitting in the sun it had no hold anymore...) and empty it out.

That gasket doesn't look quite right, the one I need is this one.

i.ebayimg.com/images/g/kc4AAOSwEMRnK6hr/s-l1600.jpg

Any yeah, my worry is this one has already been used a few times. Just gonna cross my fingers for now and bite the bullet and order a few new ones.

Yamaha online parts lists show a part number of 156-14184-00-00 which is the same as the Suzuki gasket I posted.  But you have the bike and can see what gasket you have, we can't.

Aftermarket float bowl gaskets tend to need to be replaced every time.  I have a 1964 Yamaha with the original float bowl gasket still.  Bowl has been off many times.  If you're careful hopefully you won't need to change yours.

I had replaced it when I built it, but that one ripped when I had to take it back apart recently. I had a pack of the gaskets you suggested and went to put one on and realized they were totally different. Thankfully, I had saved the original gasket, so I put that back on and crossed my fingers. So far so good. I guess it may have a different carb for the JDM bike? It's still a Mikuni round slide carb and fits all the jets, so who knows. I'd have to get a USDM bike next to it to see.

Also, thanks for the tip about the piston at BTDC. Once I read that I realized "oh yeah, the piston is the valve in this, that makes sense". Set it there for a few hours with the carb off and plug out. Did a quick clean of the carb, slapped it back together and it's happy again. Started on the second kick.

Yamaha has been known to have parts list errors too, especially on the newer "digital" versions.  I'll see if I can find an old parts book someplace and see what it says.

Parts book shows the 164 prefix part number so the online Yamaha catalogs are WRONG on the float bowl gasket.

Great job that you figured it out and already found the right part number!  

I would like to not have a bag of 10 wrong gaskets, but that's how it goes sometimes!

I'll need to get some good fiber paper and make some of my own at some point.

Annnnd it's flooded again. I guess the fuel is not turning completely off, though it's not much, the tank is about where I left it. I added a second fuel shut off that I had laying around and I will need to track down a higher quality petcock to put in over the winter I guess.

I may start pulling the fuel line off the carb if it's gonna sit more than a few hours as well.

I probably should track down an OEM rebuild kit for the carb as well and redo that, I have no idea what I used years ago, but it wasn't OEM.

On here, it’s been stated to shop original Mukuni parts.. See who has them online near about you.

Went on an adventure today! Covered 108mi of mostly back roads (sub 40mph, most sub 35) in about 8h, with many stops along the way. The bike ran great, 51.5mpg or so and only one starting issue when it was still too warm for the choke but still too cold to want to start easily without it. Otherwise it was always 3 kicks if cold with the choke or one kick if warm.

Speaking of fuel, I have been putting in 93 octane (R+M/2) since I don't know what these actually need. My choices here are 87, 89, and 93. I see in the HT-1B manual in the tech library, that it wants 85 minimum. Were they using the same AKI ratings in 1971 as we are today here in the US?

That said, I have a few issues. I reaaaaaly need to rebuild the front forks. They have spit all their oil out even though I just filled them (and they bottom out occasionally). The rear shocks are also toast, I am thinking the heavy duty 12" shocks from go powersports may be the way to go for that, I am not light and along with a backpack, I bottom them out hard fairly often. The seat is also too narrow and makes my butt hurt after a few hours.

I also received my 6V bulbs today, so I finally have right side blinkers! And I got a moped headlight with replaceable bulb, but it's slightly too small at 4.5" across instead of 5", so I am printing a 3D adapter ring to fit it to the Yamaha housing. Not perfect, but it will do for now.

Anyway, here are some pictures from today.

imgur.com/a/sCzcFbm