How many turns?

[Brad]

After riding tonight for 2 hours, I finally seen Bret again. He's the older gentleman who was the mechanic at our local yamaha dealer from the mid 70's till 2002. We had a discussion on my 78xs11, which he seen a few times and worked on a few times, even say's he put it together. I asked him the question on how to set my fuel mixture. I told him I had sync'ed my carbs last month and he told me that I should have checked the mixture, as others here on this site have suggested as well. On the site I was told to set them, like a car, at 2 and 1/2 turns. Tonight, Bret told me that I should have set them at 3 and 1/2 turns. It will probally use some more fuel, but will not bog at mid rpm's. The bike idles fine, and runs fine, and like he said, bogs a bit at mid rpm's. Now I would again like to ask; What should I set my mixture at?

[cywelchjr]

That 2 1/2 or 3 1/2 turns is just a starting point. You need to adjust the mixture properly for YOUR engine, and every one is a little different. I believe if you look in the tech tips there is an article on setting the mixture.

[petejw]

theres more to setting the mixture screws
than just turning them out a certain amount of turns,
2 turns out would be a base setting on most carbs ive
worked on, but this usually alters.

the stock setting for our carbs are 1 and a quarter turns out,
but most on here would have them set richer, me included.

different factors can also affect mixture settings such as fuel float levels.

do a search on here, theres a cpl of good threads about setting the mixture screws.

[mro]

According the factory manual, there supposed to be 1 ¼ turns out.
I use that as a starting point. Adjust the idle to 950/1,000 RPM,
synk the carbs, then adjust the pilots trying to maintain the RPM between each adjustment. Then re-sync and road test. Check the plugs. Make further adjustments if needed.

As a side note, most of the XSes I’ve worked on had/have stock air box and exhaust.
It’s not unusual for the G and H to run just a little lean with stock carb parts although you can set the pilots pretty good.

different factors can also affect mixture settings such as fuel float levels.

As well as coils/wires, old plugs and caps…


mro
PS, mine don’t “bog at mid rpm's”

[trbig]

PS, mine don’t “bog at mid rpm's”

Oh... never mind. I thought you said MIND don't bog and I was gonna argue.


Tod

[DGXSER]

Geez, mark this one down in Guiness, Tod was gonna argue and didn't!!!

[trbig]

Mark it down in Guiness??



Mmmmmmm.... Beer.


Tod

[daveyg]

Alot of the mixture setting in my experience will depend on modifications and altitude. When I worked at the Stealership we would set every new bike out of the crate at 3 turns out, the book said something like 2 1/4, but I was told it was for our altitude (3,500ft in the valley-6,000ft in the recreation areas) But if a bike got diff pipes/air cleaners, we would use a exhaust sniffer to set the mixture, and it would usually be an extra 1/2 to 1 turn further out, depending on the mod. I'd say go out an extra 1/4 turn on each carb, take it for a spin, paying close attention to your midrange, then another 1/4 turn, ride, another 1/4 turn, ride, and just find what setting limits your "bog" the best. Just be sure to get them all the same, be repetitious, and uninterrupted, to make sure not to do one twice, or one not at all.

[Ivan]

I am still tweaking on mine. Its hard to keep them upright and running long enough to tune them it seems. BUT, the best setting I have found for idle mixture is to richen them until they start to lope at idle, then go about 1/2 turn lean or until the idle cleans up. Its counter intuitive since I was always taught to set idle mix at lean dropoff and rich until the idle cleans up.

But that's just what works on my scoot. Idles and runs great. Seems to attract inattentive idiots into my safety zone though, so you may want to set your idle differently.....

[CatatonicBug]

If it makes any difference, my MNS, the one I am working on for a friend, and Bigfoot's (I believe) all run at over 4 turns out. Each carb is different (sometimes by 1/32 of a turn), but 4.5 turns out is not un-heard of.