S9 AC trouble.

[TheAmishSasquatch]

Thanks for the help guys. I think you might be forgetting the fact that the scooter was running peak & perfectly with the jets and tune that I'm currently trying to replicate. Even faster then most people claim on S9's with mine running a consistent 75-80kms on level ground.  The bike was perfect until I started cutting open the air box, changing jets and drive boss's. I am still trying to source and original box cover as I think mine may still leak (which would cause som of the symptoms I'm still having) If anyone has one they would sell please let me know. I do have a jet set ranging from 80-100/105 The factory claims a #78 or #92 IIRCC depending on AC or LC and restricted or not. An area of confusion for me is the roller weights. I've purchased the $3.99 black Chinese and Koso weights and both seem to vary significantly from roller to roller. For instance a roller A. "7g" Koso weighs 7.4g actual,  while roller B. "7g" Koso weighs 7.1g actual and yet roller C. "7g" Koso weighs 7.8g actual (and everything in between)  Whats up with that!? Are Dr.Pulley rollers more accurate? The roller that I pulled out on the bike were an off white color with one end of the brass painted yellow. These appear to be factory Kymco or possible Dr. Pulley rollers. I noticed that material and quality seems higher on the original rollers as well. The $3.99 China trash is hard plastic outer shell as are the Koso's. The stock rollers feel like rubber or Teflon or something??? Anyway, thanks so much for trying to help me out. BTW I'm in NE Philly PA

[zombie]

I personally did forget those tid bits.

The rollers you have a a graphite compound. Garbage.
Get 6-7 gr Dr Pulley or Polini rollers. They are Nylon, and can last thousands of miles.

Contact Josh @   www.thescootergarage.com/  Ask him for a drive boss. Yours might be too long/short. He can hook you up w/ the rollers, and most likely has a lid for your air box.

Sorry for all the confusion.... Talk to him, and put a "solved" sticker here.

[TheAmishSasquatch]

Thanks. I'll contact him and see what he can do for me. I guess  I'll just keep tuni9ng and tinkering until I get it tip top again.

[zombie]

Tell him I sent ya. He's the S 9 super hero.
Don't disappear on us. Updates are what keeps the forum working, and all of us learning. Thanks! 

[TheAmishSasquatch]

I spoke to Josh yesterday and did mention you sent me. He was happily surprised you still throw his name out there and is thankful for doing so. Unfortunately he didn't have an airbox/cover.  Ive been in contact with my local dealer to see how much a replacement will cost. I also plan to buy the original factory 7g rollers. I will try to update as progress occurs. The forum seemed kinda slow/dead for a while and I wasn't really doing much to the scooter anyway, so I took a leave of absence    I have tracked down a used airbox out of the UK but it looks beat and my scooter is very clean still so...     

[TheAmishSasquatch]

Ordered a new air box cover and the correct factory rollers yesterday. $45.57 out the door wasn't as bad as I had imagined from the dealership. Should be here in a week. I'll update as progress is made.

[TheAmishSasquatch]

Update: The new airbox cover and roller weights arrived yesterday and were installed last evening. The cover was a real PITA to fit, even though it is an OEM part.  I attribute the poor fitment to the fact that the original cover has been through the same heating and cooling cycles and expansions as the original air box; where the new one was fresh off the boat. After it was finally affixed to the air box, I used a heat gun to soften things up a bit and let it cool/conform to the box.  While everything was apart I decided to reseal the inlet tube from the airbox to the carb. A little fine tuning to the carb and I was off!! The bike runs well and I was able to ride about 10 miles of shake-down testing. The scoot does eventually get to 80+ Kms but not as fast as originally. This has me a bit befuddled as I'm not sure if its leaning out or the mix is too rich. Once it finally changes into top-gear the familiar hard pulling/fast accelerating performance I'm used to is restored. It used to accelerate from a dead stop in such a way as it seemed very low geared for about 3-4 seconds and then kick into a higher gear that seemed to pull and pull for days all the way up to 75-80kms. Again I;m curious as whether the carb needs more or less air/fuel??? Any help or insight is very much appreciated. I will keep updating as updates become available or until the bike runs as it used to originally.  Thanks

[zombie]

The way you find out what the carb jetting is doing is to do "plug chops". Get 3-4 new spark plugs, and install one. Ride the bike at WOT for about a mile, and hit the kill switch. When you pull out that plug look deep down to the base of the insulator. There will be a colored "ring" right at the base. It should be a dark tan to coffee color, and in a complete ring. If it is lighter in color the main jet is too lean. If it is darker in color the jet it too rich.
You can do the exact same test at any/all throttle positions. I always do this at 1/2 throttle, and full throttle, and use a NEW plug for each test.

Nice job on the air box too. I liked the idea of heating it all up to get the correct fit.
Also... You bike may have seemed peppier because of the worn/lighter rollers. The first sign that they are worn is an increase in rpm so new rollers will have reduced rpm over worn rollers.
Most people will lighten the replacements by a gram or two to get that extra rpm, and torque. You might want to keep the new ones, as spares, and get another set about a gram lighter.

[TheAmishSasquatch]

Thanks Zombie. Ive been tinkering and keep getting very close. The scoot even has that punch I remember. However the bike still lacks the acceleration/pull to 70-80kms. I did notice (thanks to the digital tach I installed  ) the pipe comes on at around 3200/3250-about 3300 RPM and pulls hard to a top speed 70-81.5kms maintaining 34xx-35xx RPM. When the bike is accerating I feel the certain punches and pulls I remember but then drops from 3050-3080 RPM out of the powerband/pipe band to 29xx rpm. Its at that point I need the bike to gain an extra 100-200 rpm , not drop em!!! I was thinking of using the cheapO ebay 6.5-7g rollers i have as spares and as you said keep the OEM rollers for back up (just until I order OEM 6.5-7g rollers). The absolute biggest question I have is "what is the effing idle supposed to be set at!?"  Ive read 1900 +/- 100 (seems waaaay too high), and I've seen 900rpm.  Today I set it around 1820-1880 (after the motor idled down to steady on center stand) and noticed at stop lights with the bike on the ground + me, it was idling around 16xx rpm. The bike ran great with the exceptions of top speed/pull noted earlier but these settings burned through a half tank of gas in about 15 miles!!!  This leads me to believe 900rpm is closer to spec, but when adjusted to 900rpm idle, the bike is a slow turd and 55-60 kms is about all she's got captain.  Any help would be great. Thanks!

[zombie]

When the bike looses accel. from a reduced idle it is showing the idle jet is too small, and the bike is way too lean at such low rpm.OR the idle jet is too big, and the bike is flooding at low rpm. Have you been adjusting the MIX screw every time you changed the speed screw?

Set the idle around 1200, ansd adjust the mix screw for the best idle. Try that, and see how the accell. is. Then turn the screw 1/2 turn either way to see what result you get. If enriching the circuit helps then a larger idle jet will help or vice versa.

Also your slide needle should be adjustable. If you need more fuel to accel raise the needle 1-2 slots. If you need less fuel lower the needle.
In either event changing the pilot jet to match what the screw/needle indicate will get you back to setting the needle, and screw back to their standard settings. 2.5 turns out for the mix screw, and center slot for the needle.

I hope that all makes sense....

[TheAmishSasquatch]

Thanks it does make sense, and I have been adjusting both individually as  well as in conjunction with each other (I'm trying every combo to see what works).  The "Throttle stop" screw seems to have more of an effect on idle. The "air screw" has an effect as well but seems more important in  WOT operation. I wish I could adjust the needles on the fly, while riding. This is what I have planned:

I will turn both screws in until seated. I'll adjust the throttle stop until 1200 rpm. I'll then begin to adjust the air screw and see where that take the idle/throttle response. I'll then adjust the throttle stop acordingly to the point where the back wheel just begins rotation (in the event the air screw adjustment sends the idle into the stratosphere as has happened). Looking for an idle of between 1200 and 1500 or is that too low/high?  Is 1900 the correct factory spec?   Once I'm happy with those settings I will swap to the cheap rollers 6.5-7g.  Does this seem legit? Thanjks.  BTW its getting cold as F*** riding the scoot   

[zombie]

You sort of have it right...
The idle Stop screw is the larger one. DO NOT turn that all the way in. Chances are the engine will blow.
I don't know the OEM rpm but 12-15 is normal for mine. 18-19 is ok. same for 9-11.
Anyway get it around 12k, and then turn the air screw either direction to the highest rpm. If you have to turn down the stop screw that is a GOOD sign. Keep doing that until the idle is around 12k, and no matter which way you turn the air screw the idle goes down.

That air screw has a very limited effect on wot. Because it only corrects the air/fuel ratio at idle, and maintains that ratio only up to about 1/4 throttle. The needle manages that ratio from 1/4 up to about 1/2-3/4 throttle. From 3/4 it is all on the main jet.
Yes they all interact, and are very dependent on each other. To some degree they can/do compensate for each other but not in a perfectly tunned bike/carb.

It is a bitch riding/swapping/riding/swapping but it is worth the effort for a long lived engine.
Besides having about 20-30 jets for each carb type I also have around 10 needles for each one. Thinner/thicker/taper rates.

What I do is set the idle, and ride ONLY on 1/2 throttle or less. Do this w/ a brand new plug, and look inside for the coffee colored ring. Tan is too lean, and black is too rich.
Once I get a good plug chop I will start playing w/ the main, and repeat the plug chop but this time at 1/2 throttle, and again at wot. 3-4 NEW plugs, 5-6 jet swaps, and it should be good to go.

Pick a WARM day for all this. If you jet below 50ish degrees it will be wrong when it warms up.

[TheAmishSasquatch]

Thanks for the clarity on the adjusters. I know its close, but still could be perfect IMO. I'm just trying to get it ride-able  as a back up means of transportation. I figured with such low temps and cool dry air the mix would be lean but still wanted to try and get it running as close as possible. It's probably gonna have to wait until spring, but come spring I'm hoping to get a left over stock SR50 lol.  Love the S9 but I love the Aprilia more hahaha

[zombie]

Then you will need to talk to Richard from High Gain Tunning!

He's built the fastest SR-50 there is. They are his bread, and butter. All in figure around 5k for a 7o mph beast

He has never posted the real number but the bike pictured is near 25k in parts/labor.

[TheAmishSasquatch]

Turbo setup? If so, thats a very clean install.  The bike I'm after is an SBK. $3200 with dealer de-tune/flash. 55+ mph off the show room