RS FLATSLIDE goooooroooooo's needed

[Guest]

Alright,

Here is my problem.
1166cc, pods, header, stock cams, 36mm rs flat slides.

pilots, 17.5 afr @ idle is 12.9-13.3 (I like that)
mains, 125
needle, center groooooooooove
floats, 18mm
screws, 3 turns

idle is fine, 1/8 turn off idle @ 3-4k rpm afr takes a dump 10.5-11
Whus Up?

Wouldn't care much cuz, it goes like a sculded dog, but that is right in cruzing zone and I would like to know how when its still on pilots how it richens up so much. Emulsion tubes to large maybe? first time this problem has croped up. Also, when I drop the needle to top grove, no difference.

I R R I T A T I N G

Thanks dudes, If I hadn't been a stuntman for 25 years my brain may be in better shape.

 

[posplayr]

what is WOT AFR? U think mayB AFR drop on Accel Pump?

 

[sharpy]

On my chart 36's on a 1150 should have 130 mains. and the screws 1/4 - 1/2 turn. Other than than im lost sorry

 

[rapidray]

Rob, back the accellerator pumps off all the way & try it again. You WILL be surprised. Ray.

 

[Guest]

boy oh boy. I guess I should have said so but I didn't. the pump isn't in play @ 1/8 throttle.
I took the pump out of play anyways and by 1/4 throttle or better the afr comes back to upper 12's.
The bike is strong when on it. It's the bobble @ cruz that is buuuuuuugin me. Haven''t had it on any of the other bikes.

 

[Guest]

what is WOT AFR? U think mayB AFR drop on Accel Pump?

Jim, have to work from pilots up. Haven't got the numbers for wot yet. But I am gussing from the wheel coming off the road that its pretty good.

My first thought was the A-pump might be out of adjustment but it wasn't.

 

[posplayr]

Jim, have to work from pilots up. Haven't got the numbers for wot yet. But I am gussing from the wheel coming off the road that its pretty good.

My first thought was the A-pump might be out of adjustment but it wasn't.

maybe your three screws out is masking an issue. Only problem is other links like this suggest you should be lean down low and not fat. If you bump up to a 20, and screw the mixture screws back in you are closer to the standard configuration.

I have never messed with the RS, but seems like the same tuning issues as the CV carbs no?

Your using an AFR gauge with no data logger right?

http://www.gixxer.com/forums/showthread.php?t=125789

I would have to agree with going up on the pilot jet . Try going up one size which should be a 20.0 . Mikuini recomends 1/4 to 1/2 turn out on your pilot mixture screws so 1 1/8 turns out may be helping with covering up the lean problem. Double check the bench sync when you have them off again.

http://www.carbparts.com/mikuni/mikuni_rs_standard_tuning_specif.htm

 

[posplayr]

boy oh boy. I guess I should have said so but I didn't. the pump isn't in play @ 1/8 throttle.
I took the pump out of play anyways and by 1/4 throttle or better the afr comes back to upper 12's.
The bike is strong when on it. It's the bobble @ cruz that is buuuuuuugin me. Haven't had it on any of the other bikes.

Are you using the Innovate AFR gauges? Those meters are supposed to be hypersensive and go bonkers unless you are close in AFR.

Also this is particular bike is different from your other tuning of similar bikes?

 

[Guest]

maybe your three screws out is masking an issue. Only problem is other links like this suggest you should be lean down low and not fat. If you bump up to a 20, and screw the mixture screws back in you are closer to the standard configuration.

I have never messed with the RS, but seems like the same tuning issues as the CV carbs no?

Your using an AFR gauge with no data logger right?

http://www.gixxer.com/forums/showthread.php?t=125789



http://www.carbparts.com/mikuni/mikuni_rs_standard_tuning_specif.htm

The sinc is fine. The problem isn't lean, its rich. The pilot isn't the problem as the afr is good at idle. The fuel screws are good to 3 1/2 turns. If I go up to 20 on the pilots my idle will be too rich and will over heat. I took the 20 pilots out. I am using an LM1 with logger and read out.

 

[posplayr]

The sinc is fine. The problem isn't lean, its rich. The pilot isn't the problem as the afr is good at idle. The fuel screws are good to 3 1/2 turns. If I go up to 20 on the pilots my idle will be too rich and will over heat. I took the 20 pilots out. I am using an LM1 with logger and read out.

So did you run it with the 20's? How was the mixture screw set then?

I found I got my most reliable readings for the 1150 carbs when I pulled a big hill and let the carb stabilize for 10-20 sec on a fixed throttle setting. Going through the gears made the AFR bounce around. You have mechanical slides I know, but I have even seen EFI bikes with AFR pretty dynamic.

Anyhow what is different about this bike?

 

[Guest]

So did you run it with the 20's? How was the mixture screw set then?

I found I got my most reliable readings for the 1150 carbs when I pulled a big hill and let the carb stabilize for 10-20 sec on a fixed throttle setting. Going through the gears made the AFR bounce around. You have mechanical slides I know, but I have even seen EFI bikes with AFR pretty dynamic.

Anyhow what is different about this bike?

20's were too rich, nothing different about this one. Every engine has its sweet spot but this one is a pain in the........
May be a carb issue and not the engine.

 

[posplayr]

20's were too rich, nothing different about this one. Every engine has its sweet spot but this one is a pain in the........
May be a carb issue and not the engine.

trying to figure out if the pilot fuel screw increase fuel when it goes out
http://www.mikuni.com/pdf/rs_app_parts_lists.pdf

of is like a pilot air screw which decreases fuel when it is out.
http://www.mikuni.com/pdf/vmmanual.pdf

the maunal seems pretty specific the pilot fuel screw should not be out more than 1/2 a turn so seems you are over compensating for something.

 

[GregT]

In my experience with the RS's what you're calling the idle jet is actually a slow run jet. Changing this will usually not affect a/f ratio at idle - but off idle and up to where the pumps usually come in this jet has more affect than the needle shape or placement.
I'd try what others have suggested and go richer on the slow runs - if adjustment of the mixture screws is needed to get your idle mixture right, well there's plenty of room there. When the combo is correct the standard screw settings should be what you finish up with.
I'm also pretty sure that opening the screws richens the mixture so by having them so far open you're covering a lean area which richer slow runs will correct.

 

[Guest]

trying to figure out if the pilot fuel screw increase fuel when it goes out
http://www.mikuni.com/pdf/rs_app_parts_lists.pdf

of is like a pilot air screw which decreases fuel when it is out.
http://www.mikuni.com/pdf/vmmanual.pdf

the maunal seems pretty specific the pilot fuel screw should not be out more than 1/2 a turn so seems you are over compensating for something.

1/2 turn is their standard setting for every bike on the planet. I have had lengthy chats with the Mikuni tech about the fuel screws, which richen the mix as turned out. He told me they are good up to 3 1/2 turns which is varified with my sniffer. He isn't there this week so I can not talk to him regarding this little issue.

 

[trippivot]

First - if your idle mixture screws are out more than 1 turn you have the wrong pilot in there.

a 17.5 pilot at over 3 turns is worse than a 20 at 1/4 turn

At 3 full turns in a RS the fuel in the pilot circuit is uncontrolled and flowing at 100% before the slides are even opened.

Now I hear that you state 20's were too rich?? boy the step from 17.5 at 3 to 20 at 1/4 is actually leaner off idle if the slide needle is set lower to accomidate street riding.

SO, by using our common sense we know something else must be going on

what HG setting did you place your carbs at when you synchronized them?

Too little or too much idle vacuum can be your core tuning issue. re-set them in the range of 18~22 HG at a 1100 rpm idle. your specific bike and altitude may vary a little off of 20cm-hg. but this is a big mechanical carb detail secret.

CV's are automatic ( hence the vacuum operated diaphram) and set themselves to the altitude you are at, however mechanicals can be synced' correctly to each other but to the wrong vacuum height. This causes all sorts of mysterious jetting problems

 

[Guest]

I will check. thanks.

 

[BlackStar]

I wouldn't consider myself a guru, but on my GS1085 with RS34's my fuel screws are set to around .5 to .75 turns out. 17.5 pilots. Plenty of fuel range indicated by running and smell (unscientific) Sorry, no cool toys for AFR numbers. Header, pods, stock cams, small port heads matched to intake boots.

 

[paco13]

So, what did you end up with.

I have a like setup, aside for bigger cams and valves, and had the exact same issue.
No a/f meter but symptoms showed the same.

I ended up with;

Floats @ 17mm

#10 pilots

needle @ middle groove

140 mains

screws @ 1.75

acc. pump comes on @1/4 throttle, off @3/4 throttle

 

[paco13]

Check your ignition advancer and the magnetic trigger/rotor? also.
I have a dyna-S. It had a little slop in it, just a little, and it made a huge difference @ cruise when swapped out for one I had from a 78 750 with no play. Probably should check this first before trying to jet carbs.

 

[Homie]

Here is my problem.
1166cc, pods, header, stock cams, 36mm rs flat slides.

pilots, 17.5 afr @ idle is 12.9-13.3 (I like that)
mains, 125
needle, center groooooooooove
floats, 18mm
screws, 3 turns

idle is fine, 1/8 turn off idle @ 3-4k rpm afr takes a dump 10.5-11

I have a very similar setup but more cam (see my signature tag below). Remember the fuel "circuitry" in the carb is accumulative from the idle circuit all the way up to the mains. As the throttle is opened each successive circuit builds upon the previous ones until you have them all flowing at WOT. Since they build upon each other it is very important to get the "foundation" (idle) right before moving up to the next level. As we all know the manual slide carbs are more sensitive to tuning and less forgiving than the CV carbs so getting them "right" is a bit trickier". So, here is my two cents worth on the subject:

1. To me, 3 turns out on the idle mixture screws seems way too much. Installing the 20 pilot jets should allow you to turn the idle mixture screws back in to a more reasonable 1 turn or so and still achieve the desired AFR.

2. At an 1/8th turn on the throttle is approx where the needle-jet / jet-needle (nj/jn) circuit kicks in and adds to the flow from the pilot jets. Since the AFR decreases at this point I would assume that the overly rich condition is a result of the pilot jet circuit being off (see 1. above) or the taper of the jet-needle being too abrupt where it comes off the needle-jet seat. No where did I see you mention the jet-needle number (or needle-jet number either for that matter). It could be stock or someone could have changed them in the past before you got them. I would check the profile of the taper on the jet-needles.

3. I suspect that the pilot jet circuit is the root of your problem. So if it were me, I would get the pilot jet circuit corrected first. Then, I would examine the jet-needles / needle-jets and see if they are stock or one of the recommended alternates and correct if they are not.