have stock carb, what jets to order?

[chaz35]

Got 2003 S9 LC to run and drove around the neighborhood some.  Runs OK, but appears lean, very slow to warm up, boggs at lower rpms.  When it comes up on the pipe it takes off, but I hesitate to push it until I get a chance to test it out more.  Air temp was in the 40's fahrenheit all day, so fairly cold.

Service manual says carb has #92/ #78 main jet (unlimited/ limited speed) and #35 slow jet.  When I took carb apart to clean, jets didn't have any markings that I could recognize, so I don't know what I have.  Also, the CDI green wire is connected, so I think it's still restricted.  Scooter has nice expansion chamber, I think came stock with it.  I think CVT has been opened, but didn't seem to slip that much, but really don't know if modified.  I plan to keep stock airbox, because of nose concerns.  I know from kart racing, the loudest engine sounds come from the carb, not the exhaust.

I did some research, I think I have Keihin PB16 carb and found I can order some jets from jetsrus, thanks to some postings on this site.  Any recommendations on jets to order, main and slow?  Assuming I have #78 main jet and #35 slow jet.  Thanks

[Triesandluth]

I wouldn't mind knowing as well.  Probably won't get around to upgrading the carb until spring.

[tortoise]

very slow to warm up, boggs at lower rpms . . . temp was in the 40's

Cold fuel related discussion.

[chaz35]

I don't know what to do, so ordering following:  90, 92, 95, 98 main and 38 slow jets.

My logic is, I think carb has 78 main jet/ 35 slow jet right now, because I think the cdi is still restricted (green wires are connected) and service manual says carb jets are 78 main/ 35 slow if limited.  Unlimited should be 92 main jet/ 35 slow jet.

I saw post People 50 section where went from 70's main/ 35 slow to 90 main/ 38 slow and was easier to start and ran a lot better.

Once I figure out what my carb jets are I can go from there and order more jets if I needed.  Cheers

[Triesandluth]

Ah.  When all else fails check the manual!  I think I'll go for the ninety two.

[chaz35]

I know slow jets not supposed to effect wot, but my experience, if you go up on the slow jet (idle jet), it will richen top end.  So, I ordered a 90 main, because I also plan to go to a 38 slow jet.  I am thinking it will run like a champ when I get the right jets in it.  We will see.  Cheers

[Triesandluth]

Definitely keep me posted.  I would like to know the outcome so I can copy you.  That's if I don't get to doing the bbk first

[chaz35]

By BBK do you mean aftermarket airfilter?  I may do that at some point, but for now just want to get stock airbox to run right.  Today it was warmer, and started up easy and ran a lot better, but I think still lean.  I will post update as soon as jets come in and I can try them.  Ciao

[Triesandluth]

Big bore kit.  Make it seventy CC

[BettinANDlosing]

I know slow jets not supposed to effect wot, but my experience, if you go up on the slow jet (idle jet), it will richen top end.  So, I ordered a 90 main, because I also plan to go to a 38 slow jet.  I am thinking it will run like a champ when I get the right jets in it.  We will see.  Cheers

Slow jet and mixture screws both effect ALL throttle positions. Drastically at less than 1/4 and less the higher the throttle opening, but it does have an effect at WOT. have a peek at this: http://www.mopedarmy.com/mediawiki/images/thumb/7/72/PHBGGraph.png/286px-PHBGGraph.png
It's for the Dellorto PHBG but the same principals apply to all pull slide carbs. Just look at that chart and picture it when your riding your scooter, if you can try to find the "transfer" where the jets change from idle, slide, needle, and main then you will have a much better chance of trying to successfully tune your carb. Depending on your bike if you can cover the air intake with your hand to determine if its lean, if it is your bike will pick up in rpm if its rich it'll start to choke out and slow down.

[zombie]

Hey guys... I just posted earlier that the colder the ambient temp is, the denser the air mass. This alone creates a lean running condition on all smaller carbed engines.

Back on topic both of you can't really guess at what jet is correct. You have to go thru the trial/error process.
First things first. The ideal position for your idle MIX screw is 2.5 turns out. This is a fuel metering screw so turning clockwise is leaner, and counter is richer. Depending on where your bike idles/snaps the throttle best will tell you if you need a larger pilot jet. If it responds better at three turns go bigger.
That jet does carry over into the main circuit when running on the main so it will affect the rest of the jetting.

I would buy a set of jets from 86/88/90/92/94, and a set of pilots from 38/40/42. At a few bucks each they will come in handy.

Get 3-4 new spark plugs as well.

Determine the pilot as suggested, and install the largest main. IF the bike runs but bogs some ,try compensating w/ the idle screw. Down to 1 turn out is acceptable.  From there it is just a matter of finding which two jets work best together, and nearest the 2.5 turn setting.

The extra plugs are to verify the overall mix ratio by doing a few "Chops". Ride at WOT for about a mile, and hit the kill switch/or key to shut down. Pull out the plug, and look deep inside the insulator for a coffee colored ring. A FULL circle is what you want. NOT black or tan but a rich coffee color.

Black means the main is too rich/tan too lean.

You should also try to do this at an avg temp for your area. Set it correctly at 40* F, and the bike will be rich in warmer temp.

Hope a bit of this helps.

The cdi I forget what derestricts them... I think it was combining the two green wires but that might be the ZX. There is info on that cdi here on the forum. You might have to dig for it.

[BettinANDlosing]

Wires unplugged derestricts the rev limit.

[zombie]

Is that the one w/ the bullett connector in the green/yellow wire?

[BettinANDlosing]

I don't think so, I'm thinking of the ones that are in like the early people 50 and sing it has two solid green wires looped into the cdi and connected with a bullet. I'm not 100% it's the same on his super 9 but knowing Taiwan it prolly is.

[zombie]

Well I know the solid green is ground. The bike may not fire w/out it but no biggie... Just re-connect it.
I seem to remember the S9 had a simple bullett connection right at the cdi that you just pulled apart. That was one model, either AC or LC I forgot. The other you have to buy an adapter/cdi to de-restrict.

If the bike has no obvious pull apart connector.... Racing Planet has the proper kit for the bike you have, and I think they are around 50 bucks now. They used to be about 100 more.

Either way as I remember the pipe hits at 7.5k/peaks at 8.k. The power stops at 9k. but you should be seeing 60mph by then if not a bit more.