"Batcave" project #2; My Kymco L.C S9 build & tune

[90GTVert]

If it takes a while to rev down, that's usually lean. If it dies down and wants to die out, it's often rich.

Inlet/Air Filter side mix screw should control air. Outlet / Intake side screw should control fuel.

Doesn't surprise me that the carb needs some fine tuning for cold weather.

If you can't get good results out of the mix adjustment, you could see if a change in needle position makes any difference. Never hurts to be sure everything's clean either.

[vvtr]

Jan 3, 2012 18:40:18 GMT -5 90GTVert said:

If it takes a while to rev down, that's usually lean.

+1
look for airleaks around the intake as well... try spraying a bit of carb cleaner or wd40 around the intake rubbers when it's idling.
(take care to miss the exhaust though lol - a mate set fire to his bike doing this!)
if there are any leaks on the intake, the rpm will rise when it sucks the solvent in.

if there are any leaks you will really struggle to get it jetted properly!
i doubt this is the case with your scoot though as you seem to be well on top of it....
jetting can be a pain, especially after fitting a bigger carb.

best tool i ever bought (nearly 30 yr ago lol) was a 'gunson colortune' kit...
basically it's a glass spark plug that lets you see the colour of the burn.
you're looking for a clean blue burn then for a 2t go up a main jet size or 2 to be on the safe side at full throttle.

you can get them to fit all plug sizes & adaptors for the smaller 4t plugs.
for awkwardly positioned plugs there's a flexible fibreoptic adaptor so you can see the flame from the side.

have a look on ebay - well worth the £ (or $) especially if you do a lot of meddling - they last forever if looked after and are an absolutely brilliant tool for getting carbs set up right without paying someone a fortune to do it for you on the dyno.

here's one in use....


& this is what you can expect to see on a nicely fuelled engine...

in that last clip you can see how the colour of the flame changes as he revs the engine and settles back to idle.... white for lean, yellow / orange for over-rich, then settling back to blue for good clean mix

[90GTVert]

I've never even heard of those. Neat. Learn something new every day.

[2strokd]

Me either! Thanks for sharing that!

[Thebatman]

Well i am back again to ask the same old questions about a c arb. I tried to find the post where i asked about KNOWING if your lean or rich but now i cant find it. WTF, I KNOW i posted about it..
Anyway, i had been riding a different scooter because of the worrys about my s9 but of course that scooter died on me in the middle of a hail storm on wed. so i HAVE to ride the s9 now. I was playing with the carb again... I am not able to order anything atm SOOOOO, this is where it gets real complicated... The carb was at the running settings, COLDER weather has hit and now she doesnt run. It was only spuddering, COULDNT make it out of the drive.. That means rich,correct??
Ok then, i lowered the needle 1 notch, not QUITE as bad but still very spuddery. Lowered the needle again to the bottom. FINALLY got her started. Installed a 25pj since the needle was all the way down. Yesterday it was in the high 40's, LAST NIGHT in the 30's it didnt want to start.
THIS morning, she started fine, smoking good at idle BUT when i go OVER 1/2, she spudders terrible all day today from school...
Spuddering means rich,correct?... HOW could/would she be rich with the same mj, needle all the way DOWN?
If i raise the needle, she will spit/spudder worse and i can't lower it anymore..

**Is it even possible that the mj could be a tad to rich at 85 causing this NEW spudder above 1/2? (i do not understand how that could be feasible with the same needle all the way down now, she should be leaner,correct?)
Leaner will cause it to lose evrything and go silent,correct?
Richer would cause a spudder or spitting or "bog",correct?
I am trying to play with jets and the s1 needle since i cant get a Q1 needle to try.(thought going up on the pj would have the same effect as using a smaller needle)
THANK YOU ANYBODY/EVERYBODY FOR ANY ADVICE/INPUT IN ADVANCE

[190mech]

Hey Larry, When are you gonna throw that crappy carb away and get a good one??What kind of airfilter/airbox do you have?
Yep sputtering sounds rich,whats the spark plug say?What kind
of spark do you have(fat blue?)?
I know its more questions than answers,but dang,the S9 should have been running strong last year!! :stumped:

[Thebatman]

Jan 13, 2012 19:46:01 GMT -5 190mech said:

Hey Larry, When are you gonna throw that crappy carb away and get a good one??What kind of airfilter/airbox do you have?
Yep sputtering sounds rich,whats the spark plug say?What kind
of spark do you have(fat blue?)?
I know its more questions than answers,but dang,the S9 should have been running strong last year!! [/quote



Arreche is SUPPOSE to be a good carb.... Supposedly the best for the s9
I'm a broke shit these days, so that isnt going to happen.. I do have a brand new OKO 21 BUUUUT, i couldnt "tune" the 24mm(zx carb), so what's the chances of tuning a 21?
I had went back to the oem airbox awhile back.(again, supposedly the best for the arreche s9)
Yep, the spark is a nice blue spark.
The scooter was running pretty decent before it went to 30 degrees outside...(ended up with a silent,powerloss dead spot at 1/4) I don't see HOW i can LEAN the needle out and THEN be rich. The mj stayed the same.
I didn't look at the plug since i wasnt wo as i was coming home but it definately spudders anywhere past 1/2 today.(high was 36)

[Thebatman]

I had started it up just now and revved the fk out of it, spuddering the whole way and the plug is black and dry.
HOW is it possible to be rich at that point when the mj wasnt changed?
HOW is it possible to be rich anywhere when i leaned the needle all the way out.? The mj should be leaner now not richer(plug used to be dry rusty color)
Cold weather means bigger jets

[vvtr]

could be the oil pump is a bit over-adjusted....
and is it spaking right? the black could be unburnt fuel from poor ignition?

also wondering if your choke is working?? is it an electronic type?
may be worth swapping it out for another just in case it's bust.
i much prefer a manual choke myself.

[190mech]

As vvtr said,CHOKE?
An airfilter element that is very dirty will cause unexplained rich running also..

Try a fresh plug too!!

[Thebatman]

I hate to say this but i was in such a rush to get it running for school that i did not even have an filter element inside the box.
I have a manual choke on this carb.
I actually have the oil pump zip-tied open to the "correct position".
A fresh plug? Ha, that's another issue that i hadnt even brought up...I recently changed this plug.
For some un-explained reason, the plugs on this engine don't last but a few hundred kms. Noone has been able to get me a reason for that.
I will try a new plug, i have 2 left

[90GTVert]

Have you had the choke on this carb the whole time? I think you have IIRC, but wanted to verify. The manual choke I bought for my Arreche never did seal the passage there right and it ran rich all the time, on or off.


What is wrong with the plugs in such a short time frame? Are they getting fouled up with oil/gas or what?

[Thebatman]

Yeah, i have always had the manual choke on this carb.
I have no idea why the plugs die so soon. I have asked MANY people in this state and nobody could ever tell me why. OF COURSE, one of the guys that couldnt explain it is the same one that said NOT to adjust carb for winter months.(which makes me wonder how in the hell he has a forum,shop,business)
They are normally very dark (rustISH to dam near black) and dry