Rubber plugs for the carb

[Crazcnuk]

We've talked, a bit, about those rubber plugs that come in the MikesXS carb kit, but I was wondering...

Everywhere you look at carb parts, it mentions those rubber plugs being specifically for 80 and 81 carbs.

Many were saying that they are not needed, as the pilots get thier fuel differently than the 78-79 ones, which come with a threaded plug.

My question is: Are we missing something here? Maybe those plugs prevent excess fuel from being drawn past the pilot?

If so putting those plugs in may help in mid range cruise fuel economy and tune?

I just find it wierd that the plugs are made for the 80 81 carbs, and yet no one seems to be using them?

HAs anyone out there actually put those plugs in and tried it?

[planedick]

Sometimes...

When I'm faced with similar issues I try it just so I know. That may be the best way to find out. Just put 'em in and test the theory and let us all know what the results are. Just remember to try to keep it scientific like all other conditions the same and read the plugs before and after and mileage etc.

[TopCatGr58]

Hey Cnuck,

Well, from close inspection of the 81 carbs, and seeing that there is NO channel between the pilot tower and the main jet tower, there is NO way for fuel to get into the pilot jet IF you plug the tower with those rubber plugs!

I thought it was you, but might have been ROB, one of the other Canuks that posted that those plugs fit nicely over the pilot SCREW holes that have to be drilled out to make adjustments!

SO....my theory is that they are for that purpose, to help seal up the pilot screw towers AFTER you have tuned the carbs, to help keep "STUFF" out of there, so they won't get clogged, etc. and possibly FROZEN like a few Xsives have reported finding theirs after years of sitting!

Now...some folks reported that they had some odd 80 carbs that still had the tunnel between the pilot and main jet towers, and so THOSE pilot jet towers needed to be plugged, and IIRC, those towers actually DIDN'T have the threaded pilot tower so you couldn't use a screw like on the 78-79 series carbs, and so a smooth snug fitting rubber plug fits the bill! YMMV!
T.C.

[81xsproject]

The set of 80 carbs I am selling right now came with the pilots plugged with rubber plugs that had been there a LONG time. I had to replace them with some from mikesxs.

[Crazcnuk]

Mine didn't have any plugs in them when I took them apart. I also assumed they were to cover the idle screws, but have since been wondering.


MikesXS calls them 'passage plugs' for 80-81 carbs.

They also sell the caps for the idle mixture screws, and they are totally different.

----------------------------------------------------------------------

Rubber pilot jet Passage Plug (Pk./2)

Fits: XS650G/H/SH/SJ/SK/SL (1980-84) stock Mikuni BS34 CV Carbs. Used inside float bowl to seal pilot jet passage -
1 used per carb

Part #48-5002 $3.00 USD /Pk/

--------------------------------------------------------------------------

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 re-cessed 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. Suggested setting position of the normally hidden mixture screw is 2 1/2 to 3 turns out from bottom.

Part #48-5012 $4.00 USD /Kit

In the Yamaha parts fiche, they still show screws over the pilot jets for both 1980 and 81 carbs

[81xsproject]

I went and looked too. But that screw #54 I don't believe to be a plug. For one it is on both the 80 and 81's. 81's definitely don't have plugs. For two it is listed as a screw and the passage isn't threaded on my 80's or my 81's and my 80's are off of a G which to my pleasant surprise is shown in the part fiche to have brass float. Which means they DO belong there. SWEET!

Here's a link to a fiche

[fredintoon]

That's no ficheing good

Hi 81,
hit that link and it says there is no picture.
Hey guys, I got an SG and for sure it don't have brass floats, it's got the odd-shaped plastic ones and the pilot jet passages have no fuel feed except straight up from underneath directly out of the float bowl.
Never mind that those plugs fit in there, installing them blocks off the pilot jets.
That's why I said put them in the idle mixture screw holes rather than toss them in the waste bin. Yes, Mike sells a metal plug for there but it must be pressed in and it's kinda permanent. The rubber bung is pushed in and can be easily pulled out again to tweak the mixture screws.

[81xsproject]

This is the pic from that link for an 80G

[IMG][/IMG]

[fredintoon]

Artist's licence?

Hi 81,
yeah, and it don't match up with reality.
If #53 is the pilot jet then #54 can be presumed to be a plug. If that plug is installed in that carb. body it will block off the fuel flow to the jet. Also #59 shows what appear to be cylindrical brass floats rather than the odd-shaped plastic ones.
It's not the only time Clymer's has mis-labelled an illustration.

[skids]

Re: Artist's licence?

The bowl drains were also different in 81 as they drained to the sides.

Originally posted by fredintoon
Hi 81,
yeah, and it don't match up with reality.
If #53 is the pilot jet then #54 can be presumed to be a plug. If that plug is installed in that carb. body it will block off the fuel flow to the jet. Also #59 shows what appear to be cylindrical brass floats rather than the odd-shaped plastic ones.
It's not the only time Clymer's has mis-labelled an illustration.

[GNEPIG]

Hey Fred, there were two styles of carbs in 1980. The one style only made it for about half of the year before Yam (or Mikuni)changed them for the later styles.
The book does not mention them,

[81xsproject]

Exactly.
AGAIN, these are 80'S CARBS in the diagram and the pic is from the Yamaha site, not the Clymers. Pig is right, there were 2 styles of 80's carbs. Only the G model had the brass floats.

[boyat68]

As was pointed out to me on my thread questioning the funny floats of the 80G that I am cleaning the carbs on right now.

There is a supplemental section in the Clymers that specifically speak to the XS1100G and the XS1100 SG as well as the Genuine YAMAHA Service Manual. Both have pictures showing the funny floats. The Genuine has three printing dates, 1st Edition - January 1979 , 2nd Edition - October 1979. and 3rd Printing - February 1981 JEM LIT-11616 - XS - 12 ( Section 10 speaks to the 1100G Starting Serial Number 3H5 - 000101 and 1100SG Starting Serial Number 3J6 - 000101

[Crazcnuk]

Mine is an 80G and it doesn't have the brass floats. It also had no plugs on the pilot holes.

I assume that the 80-84s that the plugs are listed for, on MikesXS may indicate that the XS650s continued to use the 78-79 style carbs until, possibly 84?

SInce Yamaha liked to change teh XS1100 carbs every year, the parts listings on the Yamaha Fiche may depend on where your xs came from, ie US, Euro, Asia etc

[fredintoon]

Hi Craz,
same deal with the XS650s as with the XS1100s, give or take a fuel port location or two they are the same carbs. Mike's kit is a generic, the plugs are there in case you need 'em. Knowing if you do or not is up to you.