Carburetor Jetting

[motoman]

This was on a separate spare carb bank, not the jacked up ones.

Bet a jet myster secretly changed them after dark.......

[MPittma100]

Adding Filters

While I was adding filters and cleaning the pilot jets/circuit, I found a way, different than what I have seen shown in the forums, to route the fuel lines for the filters.

Most of what I saw showed the filters pointing up right between the carbs. When the lines are added they want to kink as you install the tank. I looked at other possible options.

The one that ended up working the best - I pointed the fuel tees between the carbs straight down. Then added an extended length of fuel line and routed it back up to the filters. The longer line allowed a softer bend to eliminate any kinking. Worked quite well. Made the line hook up at the tank very easy.

You end up with 2 loops of fuel line just above the starter, but you have to stand on your head to see them. So they are not obtrusive. I have ridden since and there are no lack of fuel or running issues.

MP

[MPittma100]

Carb Jetting

According to published Yamaha (1979 XS1100SF) service information, my carbs are supposed to have the 42.5 pilot jets and the 180 pilot air jets. Next time that the carbs need to come off, I believe I will change to these larger pilot jets and see what happens. I am soon to add the Dyna coils and a little richer pilot circuit should complement the upgraded secondary voltage. We will see.

MP

[jetmechmarty]

While I was adding filters and cleaning the pilot jets/circuit, I found a way, different than what I have seen shown in the forums, to route the fuel lines for the filters.

Most of what I saw showed the filters pointing up right between the carbs. When the lines are added they want to kink as you install the tank. I looked at other possible options.

The one that ended up working the best - I pointed the fuel tees between the carbs straight down. Then added an extended length of fuel line and routed it back up to the filters. The longer line allowed a softer bend to eliminate any kinking. Worked quite well. Made the line hook up at the tank very easy.

You end up with 2 loops of fuel line just above the starter, but you have to stand on your head to see them. So they are not obtrusive. I have ridden since and there are no lack of fuel or running issues.

MP

I went from the left petcock to the right carbs, and the right petcock to the left carbs. Another way to accomplish the same thing.

[red bandit]

IIRC 78's had 210 air jets with 45 pilots and 79's had 180 air jets with 42.5 pilots. I think you could mix them, idle mixture screw will need adjusting a little one way or the other.

[WMarshy]

IIRC 78's had 210 air jets with 45 pilots and 79's had 180 air jets with 42.5 pilots. I think you could mix them, idle mixture screw will need adjusting a little one way or the other.

All Main Air Jets on all the XS's were 140 but, the Pilot Air Jets were 180 for 78-79 and 185 for 80-81.

Nice chart here... (you didnt actually believe I knew that did you?)

http://www.xs11.com/forum/showthread.php?t=73

[natemoen]

All Main Air Jets on all the XS's were 140 but, the Pilot Air Jets were 180 for 78-79 and 185 for 80-81.

Nice chart here... (you didnt actually believe I knew that did you?)

http://www.xs11.com/forum/showthread.php?t=73

Well since the '78's had 210 air jets, again I say that chart Is not completely correct!

[BA80]

That's the third or fouth DIFFERENT jetting chart I've seen that gives the same information. Is everyone wrong?

[WMarshy]

That's the third or fouth DIFFERENT jetting chart I've seen that gives the same information. Is everyone wrong?

Well, this is the only one I've ever seen so it must be right.

[natemoen]

That's the third or fouth DIFFERENT jetting chart I've seen that gives the same information. Is everyone wrong?

YES! Everyone with 45 pilots seems to have the 210 airjets.

[BA80]

YES! Everyone with 45 pilots seems to have the 210 airjets.

I wonder if that's something that was done early in the 78 model run and then changed later on because of an issue there was with that combination.

How early is your VIN Nate, and are you certain those carbs are OEM?

[natemoen]

I wonder if that's something that was done early in the 78 model run and then changed later on because of an issue there was with that combination.

How early is your VIN Nate, and are you certain those carbs are OEM?

Don't have my VIN memorized but I think it Is later in the model year.

I know may carbs had been "fixed" by PO's but why is it that so many others find the 210's too?

[BA80]

I'm just wondering why that doesn't show up on ANY of the charts. Surely thay ALL can't be wrong. That configuration would have shown up somewhere I would think.

Possibly it was something the dealers were doing to solve a specific problem when some bikes came back for warranty work. Maybe an attempt to get rid of that annoying spark knock at 4.5 - 5K some of these things have. My 80 engine did it bad but this 79 I haven't heard it once. Even with the fairing on.