My engine runs lean, stock set up

[L_Bo]

Hi all, great site first post.

I plan on adding a pipe and modify the air box on my 07 Kymco Super 9 air cooled scooter soon. I wanted to get a plug reading for baseline comparisons when I do the mods and found my plug to be white.

Why would it be white, with the stock set up? I put in a new plug (recommended same as stock) and get the same results. Carb adjustments don't affect my WOT plug chops, as mentioned it's completely stock.

What should I check? Clogged jet? Air leak (how and where to do this?) Air filter is clean, all bolts to the manifold and carb are tight and performance is the same now (3000KM) as it was when new. Could it be the pair valve now included with the scooter to meet emissions requirements giving false readings? Of course I could put in a bigger jet but imagine the stock set up should be jetted properly. I am at a loss and want to get whatever problem I have fixed before I go modding.

Thanks, pic of said plug;

 

[Big B NRG]

If it was to lean, your cylinder would have died allready. You can try to look thru the sparkplug hole (with flashlight) and see what color the piston crown is. It should be something like coffee and milk brown.

 

[tiba_karotsu]

carb settings are very lean from the factory (for emission compliance) & modifying the airbox for more airflow would make it worse & it'll make the carb harder to tune, keep the airbox stock & keep increasing the main jet +5 on whatever size you got right now until the sparkplug insulator body is in a nice light tan color.

 

[L_Bo]

thanks for the tips and I'll look at the piston color tomorrow.

I bought a used Next R pipe, it came with 6 gram rollers. I bought some additional rollers (and a set of sliders) AND a new jet from another source. the only jet they could find was a #95. I thought a 92 was the biggest that would fit the stock carb.......... in any event jets for the stock carb are hard to find.

the plug looks really white, I hope the 95 fits and provieds a good mix based on the current plug. If too rich then I might mod the airbox some.

 

[tiba_karotsu]

you can jet an AC engine bigger b'coz it runs hotter than LC, AC needs the extra fuel for internal cooling, if you mod the airbox it will mess up the jetting, have you tried tuning a sportbike without airbox? it's a PITA, even my modified aerox still runs with the stock airbox on, it goes 110kmh with a dimunitive 16mm carb.

check the stock jet size first, judging by the color of your plug a +10 from stock jetsize will be a good starting point, also go 1 to 2 steps colder in your sparkplug, for AC engines you must use a colder plug to prevent the tip from overheating & melting.

 

[L_Bo]

My local dealer would charge $100 to install the pipe, rollers, clutch spring and drill the carb one size bigger. Maybe I can get him to drill out my current jet (.036 = #92), take new readings and see if it helps on the stock set up. I'll do the other mods myself adding the pipe, the 95 jet, and see if it's good. Good idea? All tuning guides and knowledge is based on the LC version so I am kind of learning the AC version on my own.

I want a hotter plug? I am use to tuning 2 stroke Nitro RC engines, I would think I want a colder plug to help remove the heat, no? What would be a colder plug than the NGK BR8? So leave the air box alone, I would think with the right jetting or carb size an unresticted air flow would be benificial over stock.

Thanks again, still learning.

 

[tiba_karotsu]

My local dealer would charge $100 to install the pipe, rollers, clutch spring and drill the carb one size bigger. Maybe I can get him to drill out my current jet (.036 = #92), take new readings and see if it helps on the stock set up. I'll do the other mods myself adding the pipe, the 95 jet, and see if it's good. Good idea? All tuning guides and knowledge is based on the LC version so I am kind of learning the AC version on my own.

I want a hotter plug? I am use to tuning 2 stroke Nitro RC engines, I would think I want a colder plug to help remove the heat, no? What would be a colder plug than the NGK BR8? So leave the air box alone, I would think with the right jetting or carb size an unresticted air flow would be benificial over stock.

Thanks again, still learning.

$100 is too much but if i was doing the work i won't complain.

you can install the pipe & other stuff yourself, it not any different from what you are doing only it's bigger than RC. you can save a lot of $ by doing the work yourself, it doesn't take a genius or professional to tune these scooters for road use but it's another thing if you want race performance.

i think you misunderstood me, i didn't say get a hotter plug, please read my previous post again it says get a colder plug, what's colder than a BR8? there's BR9, BR10 plugs if you know where to look. i use a Denso 31 (equivalent is 10 for NGK) plug on my LC engine, it was one of my old plugs i have been using on my dragscooters, works fine as long as you tune the carb not to run very rich.

some stock carbs are impossible to run with modified airbox or even without airbox b'coz the jet needle is too thick & no amount of rejetting can fix it unless you modify the emulsion tube which is pretty risky, this the common problem new scooter tuners do, they tend to fack up the scooter more than improving it so save yourself the headache & leave the airbox alone, comcentarte on other areas that make real improvement.

 

[L_Bo]

Great, thanks again for the help. Can't wait for the jet and new rollers to come in so I can start wrenching and perform my first mod.

<----- leaving airbox alone.

 

[Areomyst]

Great, thanks again for the help. Can't wait for the jet and new rollers to come in so I can start wrenching and perform my first mod.

<----- leaving airbox alone.

Good to see more Super9's around. Be sure to check out scootertrog's project page, he's done a lot to it. I assume you're in the States, where at might I ask?

Keep us posted!

 

[L_Bo]

Good to see more Super9's around. Be sure to check out scootertrog's project page, he's done a lot to it. I assume you're in the States, where at might I ask?

Keep us posted!

Scootertrog is a member here? Awesome, he's a huge contributor to the Yahoo Super 9 group and I have followed many of his posts as well looked through pictures of his projects. He's real knowledgable, has replied to just about all my posts over there. Thanks to him and the "files" section I have already done several "asthetic" mods such as turn signal relocation, rear fender fix, and adjusted my fuel guage. The A/C version of the Super 9 is a little different as everyone has the L/C version so some things are a little different with reguards to tuning.

I already had 2 other topics on the yahoo group, didn't want to add a third one about my plug readings :#

I am in Delaware, on the Maryland line at the beach. (Ocean City MD / Fenwick Island De.)

 

[Areomyst]

Scootertrog is a member here? Awesome, he's a huge contributor to the Yahoo Super 9 group.

He created the Y! Super9 group. Scootertrog's got a strong passion for his scoot. I'm on there too as "Areomyst@hotmail.com". Unfortunately I don't have a Super9, but I've worked on and tuned a bunch of them.

The air cooled super9's aren't too bad really. I don't like the catalyst system. We often cut off all the expansion tubes and weld them back together as part of a basic de-restriction.

Did you see Scoot Magazine's 50cc Shootout? The Super9 came in as the top performer. I think they had a typo though, because it says "SOHC 2 stroke". Why doesn't my Kymco People 2t have an overhead cam?

Let us know how your modifications go.

~Josh