needle valve 80G

[mro]

recently aquired an xs11 80G
(title said it was an 81)

when got it started, small back fire thru carbs
(blew off fuel vacuum lines)

started closer inspection of carbs
found one needle valve damaged beyond use, looked like it had been drilled.

anouther slightly damaged (fixed slot on top w/hack saw)

removed carbs, R&R bad needle valve
cleaned and adjusted then reinstalled

started w/needles out 1 1/2 turns

started engine, ran good (11/1200 rpm)
after warmed up gave it a little gas
RPM to 3K then let off
RPM would only drop to about 2500

long story short
have all needels out 6 1/3 turns

runs very good, idle 1150, very good excell through 7000 RPM
(haven't cranked above 7000 yet)

I'm not a bike machanic, but i can't help but think I've got something screwed up.

exhaust pipe 1, 2, & 4 are sorta gold colored, 3 is blue

have not been able to find any info on adjusting needle valves

any help out here???

mro

[RiskyBusiness]

Just to make sure I understand... Its running strong but you feel you have the needles screwed out too far? You see signs of running lean in at least one cylinder (blue pipe).

Did you change all the jets at the same time. One of the great mysteries that lives in these carbs is that often jets are not actually what they are labeled. As such, most folks change all 4 jets when they alter one.

Have you read the plugs for signs of mix being off or are you just reading the pipes?

Its cool that you have it running! That's a good start.

-RB

[skids]

Re: needle valve 80G

Those "needle valves" that you refer to are known as "pilot screws." If you screw them out too far, it is a sign that the "pilot jets" (accessed from the bottom of the carb body) are either too small, are clogged, or the associated passages to the pilot circuit are plugged. There are three holes in the carb throat right next to the pilot screw's hole. It is my understanding that fuel for the pilot screw area comes from the same passages as for those other three pinholes, and originates from the pilot jet. If those are stock pilot jets, you may want to keep them and clean them with a guitar string and gumout...

Here is a link for spray cleaning:
http://home.earthlink.net/~sidskids/carbs/spraycarb.htm
It is poorly written (by me) but it may help.

From the sound of things, the engine is running real lean if it backfires through the carbs, and this can muck-up a set of carbs real quick!

Originally posted by mro
recently aquired an xs11 80G
(title said it was an 81)

when got it started, small back fire thru carbs
(blew off fuel vacuum lines)

started closer inspection of carbs
found one needle valve damaged beyond use, looked like it had been drilled.

anouther slightly damaged (fixed slot on top w/hack saw)

removed carbs, R&R bad needle valve
cleaned and adjusted then reinstalled

started w/needles out 1 1/2 turns

started engine, ran good (11/1200 rpm)
after warmed up gave it a little gas
RPM to 3K then let off
RPM would only drop to about 2500

long story short
have all needels out 6 1/3 turns

runs very good, idle 1150, very good excell through 7000 RPM
(haven't cranked above 7000 yet)

I'm not a bike machanic, but i can't help but think I've got something screwed up.

exhaust pipe 1, 2, & 4 are sorta gold colored, 3 is blue

have not been able to find any info on adjusting needle valves

any help out here???

mro

[skids]

Re: Re: needle valve 80G

Sorry about not trimming the quote!

[TopCatGr58]

Hey MRO,

Cleaning/repairing JUST the pilot screws is not enough! You need to read thru the carb tech tips a bit more first, then go back into your carbs. Clean them thoroughly, and then do a good BENCH SYNCH....most likely why it wouldn't idle down, so turning the pilot screws out so much, you're just choking it down!!

Also closely inspect the main and pilot jets! Replace with verified Mikuni's if needed. Inspect and set your floats accurately.

Reset your pilot screws back to 1-1/2 turns out. Once they are properly cleaned, they will breath and flow right.
T.C.

[mro]

thanks for the input
have been checking out this site for a about two weeks
have read most of it

just got the xs-xj cd and plan to browse through it.

the needel/pilot valve that I replaced was from the local Yamaha dealer and I did "bench syncrhronize" them.

have to check if one of my vacuum gauges can be modified to sync the carbs

need to check that all of the needels are the same and in good condiction. (did not cross my mind that the dealer could have given me something other than what the bike had in it)

will pull carbs off this weekend and do a proper cleaning
and inside inspection.

Thanks agin
mro

had forgotten how much I like to ride
been just over 20 years

[2bhappy]

I was just browing around and came across Skids great write up on cleaning the carbs. One question. Sould I worry about blowing up my shop vac when I suck in those carb cleaner fumes?

Marc

[skids]

Naw, there is not enough residual carb cleaner left to blow up the vacuum! I really don't think that Gumout is very combustible anyway.

Originally posted by 2bhappy
I was just browing around and came across Skids great write up on cleaning the carbs. One question. Sould I worry about blowing up my shop vac when I suck in those carb cleaner fumes?

Marc