38mm RS carbs, 1230cc GS1100 with GSX-r head running rich

[cdnoel]

I've been tuning my GS1100/1230 with RS38 carburetors and GSX-r head for a while and I think I'm getting close. Had it so rich initially that it made the garage smell like gas when I parked it. I have PX foam, oiled filters on it and a dual feed guzzler pingel fuel tap and I'm in Colorado at 5000 feet most of the time.

I started at 145 mains, the needles at the almost all the way up second from bottom clip, 17.5 pilots, and the accelerator pump turned as high as I could get it.

I was running with a hideous stumble around 5000 rpm's and it would stall if I blipped the throttle at idle.

I've been trying to get the stall at idle to go away primarily because I'm thinking the pilot jet is the culprit here and I know I need to work on that circuit first but I have also dropped the mains and needles because of the 5000 RPM stumble was so bad and the plugs were covered in soot.

I'm now at 140 mains, the needles are down to second from top clip, the pilots are 15, the accelerator pump is turned off. It still has bad throttle response off idle but doesn't stall completely and the 5000 RPM stumble starts to act up after the engine is good and warm 10 miles into a ride or so.

Before I go to the next pilot jet down, 12.5, I'm not sure if I should try 135 mains first. Any advice to get this thing sorted once and for all would be appreciated.

 

[TxGSrider]

I would think that with your altitude that its going to be a little tougher to tune as everything runs rich up there.

 

[Guest]

Sometimes I'm not sure why I respond to certain threads, esp. when I have nothing of any real substance to add.....that being said....

The previous 2 posts might actually be on the money....you have a big bore, non-standard head, rs carbs, and are at altitude, basically a one-off setup. Obviously put $$ and time into it....what is a couple hundo more to get it perfect, and get a dyno sheet to go along with it?

all THAT being said, you might try contacting member rapidray, if anyone here knows the answer he will, and he is always willing to help a brother out....

 

[posplayr]

What I used.

https://www.thegsresources.com/_for...vate-MotorSports-LM2-LMA3-Data-Acq-Motorcycle

 

[cdnoel]

Thanks. I'll probably work on the pilot first. Add some air with the air screws if that makes the vacuum pull more and perhaps go with a thinner filter oil.

Nice to know that it has been recommended to turn the accelerator pump off till the last setting.

I was so concerned about being lean when I started I went rich on every jet and setting I could.

I will be reviewing the Mikuni manual I have to get some info I might have missed as well.

I'd like to get the new dyna 2000 ignition system and get the carbs as close as possible before I sink money into DYNO testing.

 

[cdnoel]

WBO2 Looks like a nice set up and program. I think I'd have more of a learning curve than I bargained for and spend more money than I need to that way though.

Getting the carbs sorted myself with test rides then pay for DYNO testing would probably be most economical.

 

[rapidray]

I will ask you this from a LOT of experience, did you SYNC the carbs??? It DOES make a difference!!!
Ray.

 

[TxGSrider]

WBO2 Looks like a nice set up and program. I think I'd have more of a learning curve than I bargained for and spend more money than I need to that way though.

Getting the carbs sorted myself with test rides then pay for DYNO testing would probably be most economical.

Once you get a wideband you'll wonder how you did without it. I bought mine for my atv, then used it on my other atvs and my GS. Its worth the $$.

 

[bobgroger]

I have the previous version of this: https://www.14point7.com/products/sigma-lambda-controller-free-2
$95 is crazy cheap with a new Bosch O2 sensor. Some assembly required....

 

[posplayr]

I have the previous version of this: https://www.14point7.com/products/sigma-lambda-controller-free-2
$95 is crazy cheap with a new Bosch O2 sensor. Some assembly required....

I have the complete data acquisition system that I constructed for my 1100E listed on ebay for $200; he apparently doesn't want to go there.

 

[cdnoel]

Hi Ray.

I synced the carbs as prescribed in my RS carburetor manual with feeler gauges. I didn't with the vacuum meters because this would require me to run the motor with the carburetor tops open and I figured would introduce an intake leak on all four.

My manual prescribes to use he vacuum ports for pilot jetting only.

Problem I'm having with the manual, Sudco Racing Mikuni carburetors 5th editon, is that it doesn't specify tuning RS carbs at all.

I'm at 3/4 open on the air screws and it starts to run rough at 1/4 open and then again at 1 1/4 open.

The tuning pilot jet recommendations that the manual does cover are HSR and HS. One recommends going with a leaner pilot jet if the air screw is almost closed and the other recommends richer.

 

[cdnoel]

I'm dumb. Page 16 says take off the tops and hook up the manometers to balance them.

That's all the tuning info for RS series in the book though.

I'm going to use the info on balancing from page 16, then skip to page 44 and apply HS40 tuning to my RS's.

Thanks again Ray. Most helpful as always.

I am being persuaded by the WBO2 system. Sounds way more affordable than I imagined.

 

[bobgroger]

I'm dumb. Page 16 says take off the tops and hook up the manometers to balance them.

That's all the tuning info for RS series in the book though.

Did you start with stock jetting?
"Major engine modifications like higher compression pistonsand racing camshafts may require minor tuning adjustments toyour AS Series Carburetors. But for most applications theadvanced design of these carburetors and their unmatchedsensitivity to supply an engine's fuel mixture requirementsthroughout a wide range of modifications allow these carburetorsto come jetted correctly for most applications.Before attempting any jetting changes which you feel areneeded, first refer to the carburetor specification chart in thismanual and check if your carburetors are equipped with therecommended jetting for your particular AS Series Carburetorand motorcycle applications."
http://mototh.com/files/other/carburetors/Mikuni-rs-manual.pdf

 

[rapidray]

Sync the carbs with vacuum gauges. HUGE difference over bench sync.
Ray.

 

[limeex2]

You spent tons of time and effort to get a motor you like and enjoy but you wont dyno it? I understand if you like to tinker, but there are so many variables on your motor you will use up half a riding season just getting it close. Anti up and get it done. Im a big advocate of dynos as when they are done, and done properly you have zero drivability issues and run better than new.