'80 Special stock jet size?

[Kit]

I have an '80 Special as well, and for what it's worth, here's my experience in a nutshell so far:

Started off with stock exhaust and airbox. I have both the Clymer's and the Yamaha repair manual. One of those said main jets in #1 and #4 should be 110s and mains in #2 and #3 should be 120s (don't remember off the top of my head which book said this). The last person to work on it before me put in 120s straight across. When I asked about that, the good folks here told me that almost no one runs different size mains like that and the 120s should be good, so I stayed with that. Had the stock 42.5 pilot jets.

In this configuration, my low end was great, but my upper end was jacked up. Couldn't get her above 4000 RPM. When I switched to pods, this reversed. My high end now runs spectacularly, but then I get a lot of backfiring in the low end at idle and on acceleration (but not on deceleration). Couldn't adjust it out with the idle mixture/pilot screws. Bumped the pilots up to 45s, and was then able to adjust the idle properly. Still backfiring on acceleration though. Haven't figured out the solution to that one yet.

Wish I had the total solution for you, but I'm still working out the details. Hopefully this will at least give you a general baseline to work from, though.

[mr_misfit138]

I'm in the process of rebuilding my SG carbs right now, and I found 110 mains in all four carbs. As far as I can tell, these were unmolested OEM...

Is '80 the year that the early carbs are different than the later ones? I've seen something like that mentioned somewhere in here, but I don't remember which year it was.

Either way, it sounds like I'm not going to know until I pull the carbs out and look for myself. I'll just have to wait a couple weeks, I guess.

[motoman]

BTW Kat.......by no fault of your own that info pertaining to the 81Special is NOT correct! 81Special OEM main jetting is 110's all across...

[natemoen]

Is '80 the year that the early carbs are different than the later ones? I've seen something like that mentioned somewhere in here, but I don't remember which year it was.

Either way, it sounds like I'm not going to know until I pull the carbs out and look for myself. I'll just have to wait a couple weeks, I guess.

Yes early '80 carbs are different than the late '80 carbs.

[jetmechmarty]

FWIW, my SG has a stock airbox and 4 into one exhaust. If it matters, there's a K&N filter in the box. It is jetted 110, 120, 120, 110, with 42.5 pilots. It runs great!

[motoman]

Go with the 120s as being stock for your 80 model. That chart combines the 81 and the 80. All the 81s I have seen were 110s stock (yet to find any with the mismatched 115 jets in 2 and 3). In 81 they went to 3 ohm coils and the emission laws were tightening still, so the 110 in 81s and 120 in 80s makes sense to me.

The CORRECT stock main jetting size for the 80 AND 81 Special is 110's across all four carbs. Again, the staggered jetting was for the 81Venturer only, as it came fully loaded and knowing the center two cyl. would run a bit hotter loaded down the center two stock ran 120's outside two 115's. A bit anal on Yamaha's part and was later dropped. Again, the 80-81 Specials stock main jetting was 110's across all four. Both models used DIFFERENT configuration metering rods. Longer, more gradual tapering for the Standard as it was a land yacht. The Special was a 'bar hopper' and it definitely hopped with the shorter quicker taper needles. Guess that makes my Venturer a hopping land yacht.....

[DGXSER]

The CORRECT stock main jetting size for the 80 AND 81 Special is 110's across all four carbs. Again, the staggered jetting was for the 81Venturer only, as it came fully loaded and knowing the center two cyl. would run a bit hotter loaded down the center two stock ran 120's outside two 115's. A bit anal on Yamaha's part and was later dropped. Again, the 80-81 Specials stock main jetting was 110's across all four. Both models used DIFFERENT configuration metering rods. Longer, more gradual tapering for the Standard as it was a land yacht. The Special was a 'bar hopper' and it definitely hopped with the shorter quicker taper needles. Guess that makes my Venturer a hopping land yacht.....

All I know is what I have seen in an 80 Special bought new off the showroom floor by a local XSive. 120s across the board. But, whatever helps you sleep at night, you go on believing.

[mack]

Confusing isn't it

I've got 5 banks of 78/79 carbs and 3 80/81 carbs banks here, and all are different jetting configs. This seems to be a touchy subject as no one can say with any degree of certainty what the original stock configurations were for any given year, hence the differences in the supplied tables and charts. Hard to jet them properly when you don't have a firm base to start counting sizes from. I'm lucky in that these are just spares that I've found or scavenged out of bike shop metal recycling bins etc. and have both the original carbs for my runners. I've dedicated and configured one set for each bike as a spare but wanted the rest set up for different mods and years. It's the old "who done it and why" game.

[Rasputin]

I have to correct my previous statement in this thread. On my 79SF I did in fact have to go up two jets sizes on the mains. The Jardine spaghetti headers were the only difference compared to the other bikes (stock pipes) I have put pods on which did not require mains to be increased.