Idle mixture screws.

[Gyrogearloose]

On the float side of the carb body, there's a long (1" ?) small brass tube that fit's into a hole on the gasket edge of the float bowl. My Q. is: Does the passage way inside the float bowl itself (at about a 45 degree angle), connect to the brass tube hole? Is it supposed to be free and clear, like blow air thru it? I put vacuum to it and it seemed to hold. ?
Thanks all.

[John]

The brass tube is the feed for the enrichener circuit (choke). It fits down into the hole in the side of the bowl. There is a very small orifice in the hole, so you may need to clean it out with a very fine piece of copper wire. It should be open. The tube should be able to hold a vacuum until the choke is opened. That is where the tube leads to.

[81xsproject]

Also, I don't know if it actually blew out, but I suggest only using compressed air from the gasket surface hole and not the bottom hole, as I think I actually blew that little starter jet right out of the tube while cleaning a set (not the set I am selling PS).

[Gyrogearloose]

Thanks guys, I guess I'm OK so far.

[Gyrogearloose]

Idle mixture screws.

Don't mean to bore you'all with this carb talk, but this is my first time "dancin' with the car-r-r-r-sbs". Clymer's recommends not messing with the idle mixture screws...but....I turned mine in to "the lightly seated position ", and found 3 of the 4 were set a two turns out, the 4th carb was 1 3/4 out. I think I remember (from past threads?), that the setting should be 1 1/4 out. ? Was this a PO's attempt to get her running? Now, should I let it be, and put it all back together, or should I start with the 1 1/4 out as a baseline? All the inards are cleaned. I noted one of the IMscrews needle wasn't perfect anymore; kinda' skinny (almost same diameter) to a certain point, then from a ring around it ballooned up in it's natural shape. the tip was kinda' bent too. Hmmmm. here I am again. Reinstall or stumble around in the dark for a new one? Suggestions appreciated.

[TopCatGr58]

Hey Gyro,

First, check to make sure that the hole in the carb throat where that distorted IM screw fits into is still open and not clogged.

Then, folks have suggested putting the IM screw chucked into the end of a drill and with some emory cloth or such, smooth out or even regrind the tip to recondition it!

I didn't check your profile before posting, but the 80-81's are more easily acquired...MikesXS has them fairly cheap.

Now that you've got the carbs cleaned out, you would probably want to start with the 1.5 turns out and then see how it responds, and then tune from there!
T.C.

PS, don't worry about reinstalling blind plug, but you "may" need the washer/o-rings for your other screws??

Fuel Idle Mixture Screw with spring, washer and O-Ring
Fuel Idle Mixture Screw with spring, washer and O-Ring - Fits: XS650G/H/SH/
SJ/SK/SL (1980-84) with Stock Mikuni BS34 CV Carbs.

See following 48-5012 text.

Part #48-5011 $10.00 USD EA.
****************************************
Mixture screw Kit - Mixture screw Washer, O-Ring & Blind Plug
Mixture screw Kit - Mixture screw Washer, O-Ring & Blind Plug - Fits: 1980-84
XS650G/H/SH/SJ/SK/SL Stock Mikuni BS34 CV Carbs. Plug covers vertical recessed idle mixture screw & keeps out contaminants. O-Ring fits under metal Washer at bottom of mixture screw hole and the engine will not idle properly if it is not present - (O-ring is often disintegrated). These parts are not shown in service & parts listings as Yamaha did not want "emmisions" related parts accessed, however adjustments were often necessary to get New bikes to run properly.


Part #48-5012 $4.00 USD /Kit

[mro]

80 carbs

What TC said,
but I would replace any that look "questionable".


mro
BTW,
I'd put all four on the bench with the points close together then look at em with a magnafiying glass. If they all look a little different or worn would replace em all.

[Gyrogearloose]

Thanks for the info and suggestions. Are you saying that IMscrews from an xs650 can be used in an xs1100?; I didn't see anything from Mikesxs that was for xs1100's. ( Maybe I should be paying attention to the carb numbers. ...another senior moment.)
The open holes in the throat of the carb seem to be host to the needles sticking through (just a little) at various lengths. ? Huh. O'well, now I have some direction and can proceed in the light. Thanks again; first time through= 2 steps forward, 1 step back.

[mro]

Are you saying that IMscrews from an xs650 can be used in an xs1100?

I've been using parts from MikesXS for the BS 34 III carbs with out any problems.
First one I got from the local Yamaha dealer, $29.00.
Week or so later found Channel 11.
Now have only stopped by the dealer to "brouse" .


mro

[boyat68]

I have been piggy backing on Gyrogearloose's thread, trying to get this 80G back on the road after 4-5 years sitting, (my bad).
I going on my 6th time removing the carbs as have not quite gotten it to idle or run smooth.

I have read in different threads that the setting for the Pilot Jet is 1-1/2 turns out from a soft bottom and the setting for the Idle mixture is 1-1/2 and 1-1/4 as a starting point. Which is correct ? 1-1/2 or 1-1/4 for the idle mixture.

Also, is the synching done withe the Air Box on or off.

Thanks for a reply.

[mro]

Pretty sure I'm the one who has suggested 1 1/4 starting point.
Think I found it on a Mikuni site researching carbs. Either will work for a starting point.

I've always synked with the filter installed too.


mro

[John]

Originally posted by boyat68

I have read in different threads that the setting for the Pilot Jet is 1-1/2 turns out from a soft bottom and the setting for the Idle mixture is 1-1/2 and 1-1/4 as a starting point. Which is correct ? 1-1/2 or 1-1/4 for the idle mixture.

Also, is the synching done withe the Air Box on or off.

Thanks for a reply.

The pilot jet should be screwed in snugly, and the pilot (idle mixture) screws should be set to 1 1/2 turns for initial startup up, and tweeked from there. Synching should be done with the filter in place, that is how the bike will be set up in real time.

[TopCatGr58]

Hey Boyat68,

We want to make sure that you are not trying to set the PILOT JET anywhere but fully seated in the jet tower next to the main jet tower!

The Pilot SCREW, or Idle Mixture Screw is on the top front of the carb, and that's what is adjusted to the aforementioned settings.
T.C.

Oh well, 2 minutes after John, sorry for the repeated info!

[mro]

Ditto

Just re-read post

Ditto John and TC


mro

[boyat68]

If I hear you correctly, The Pilot Jet, next to the main jet in the interior of the carb, with the bowl off, should be set snug at the bottom of the pilot jet tower. The idle mixture screw should be set at 1-1/2 to 1-1/4 as a starting point in adjusting the idle mixture. (I have to remove the brass insert caps to get to the Idle Mixture Screw)
If this is true, then thanks for calling my attention, as I have not removed the float bowls for the 6th time, and will correct the situation as I had set the Pilot Jets at 1-1/2 turns above a soft bottom. I have cyl. 1 and 2 running rich and cyl. 3 and 4 on the money.
I have to re-set the float height just a bit lower on all bowls and re-clean float pin no. 4 as it stuck one time when I had it on prime, but it corrected itself
I am using the clear tube method for float height and I set them just a smidge above the screw head. The 23mm as cited is hard to measure in all four carbs as the clear tube shows. I am going to lower them to level at the screw head

I have the 8 holes in the Pilot Jets as opposed to the 6 hole type. Is the difference worth changing out?

Thanks for the heads up.