I got a new to me set of carbs from SRADIATOR, now I am trying to get the bike running well again. I disassembled the carbs and cleaned them. Now they are on the bike and it is running again. I have a hesitation when I give it throttle and sometimes the idle hangs at 3k when I let off. I still need to sync them do I think that be part of the issue, It also falls in its face at about 7-8k. It will rev past sometimes. What's should I turn the mixture screws to? I have a full yosh exhaust with a shortened pipe. The jets are 130 132.5 132.5 130. Any help would be appreciated.
I got a new to me set of carbs from SRADIATOR, now I am trying to get the bike running well again. I disassembled the carbs and cleaned them. Now they are on the bike and it is running again. I have a hesitation when I give it throttle and sometimes the idle hangs at 3k when I let off. I still need to sync them do I think that be part of the issue, It also falls in its face at about 7-8k. It will rev past sometimes. What's should I turn the mixture screws to? I have a full yosh exhaust with a shortened pipe. The jets are 130 132.5 132.5 130. Any help would be appreciated
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1. You have hesitation when you give it throttle at what rpm?
2. Idle hanging at 3k is usually a sign of lean condition, what pilot jet and what is your float height?
3. Sync is not related, it is related to idle at steady state part throttle.
4. If it falls on its face at 7k, did you connect the float bowls vents to the front of the airbox?
5. You main jet stagger is backwards.
Sorry typed the main jet backwards, the hesitation is at idle revving yup. Takes a second or two to rev. I think that I have all of the vacuum hoses hooked up right. Do you happen to have a picture of where all of the hoses go? I didn't mess with the floats at all. So I do not know the height.
Pilot of 12.5 is too small, but should still work, just not ideal.
You should have seen your float height, it is far more critical than the stupid screws that everyone seems obsessed with. See my post here on it.... http://www.gixxer.com/forums/showthread.php?t=296594
They not only serve as a shutoff for the petcock and tank, but they control fuel level in the bowls, determining transition from one fuel metering device to another (notice they are at different heights relative to each other....) and likely you are lean due to a excessively high float/s meaning low fuel level, due to inverse relationship.
Here is a pice of some 750 carbs i just took. The extra tubes off the 3 manifold to the right are extensions of the vacuum ports for sync..... You should just have a rubber cap on these. Mine just make it easy to hook up a manometer without removing carbs...... (today's free tip for those paying attention).
The y-shaped tube with filter canister on the top...... Goes to the nipple on the front top lower of the airbox.
I am about to break these down and sonic clean them, they have a FP 1.7 RK, and send them to Armi within other Yoshimura MJN carbs.
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1996 GSXR 750 EX AMA, Carillo, Yoshimura, Kit airbox, Keihin FCR39, Fox, Brembo, Hindle, total loss and starter less ignition, Graves, Vortex
Motorcycle: gsxr 750 srad with a few mods thanks to the members on this site.See signature.
Posts: 8,080
Re: 96 750 Carb Help
Going off topic abit...sorry op.
Those carbs look clean.
Those biege looking round thingys on the bottom of the float bowls...what do they do?
The one on the bottom left of the picture, with that nozzle sticking out...does anything connect to that?
They have sat unused since October, is that the way you want me to send them to you, or with complimentary 129$ cleaning? X2? As the MJN carbs were not used since the summer. And, while that is not my idea of clean on the outside, it's what is on the inside that counts.
The beige caps under the float bowls are connected to the solenoid and part of a slide vacuum assist feature. The outside pointing arms you ask about, if you rebuild it right, don't have any holes in them, and don't connect to anything therefore.
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1996 GSXR 750 EX AMA, Carillo, Yoshimura, Kit airbox, Keihin FCR39, Fox, Brembo, Hindle, total loss and starter less ignition, Graves, Vortex
is it critical the mains are approximately 2.5 smaller in 2,3 than 1,4?
is this some sort of heat issue?
I don't claim to know carbs as well as I should but why isn't the needle and fuel level adjusted accordingly?
for the D&D, block offs and high flow air filter I was running 130s all the way across, just ran poorly when it got hot so I dropped em all to 127.5s I think? smaller anyways and it pulls pretty much the same up top hot or cold,
for some reason I feel theres not much sensitivity when it comes to the pilot screws, I can close one completely and yes I can hear a slight difference (tick, tick) but 1 1/2, 2, 2 1/2, not a whole lot of difference, wish I had a dyno to sniff it cuz it seems a little rich down low but thats just going by the nose sniffer..
would I be better off going 2.5 smaller in the 2,3 hole? (125s) I'd like a smooth idle and as much low end delivery as I can possibly squeeze out of her..
I know, go back to stock exhaust, anyone wanna trade a D&D titanium for a nice stocker? its so fargin loud anyways!
In the 750 srad case, always keep the stagger.
In the 600 srad case, you can run 1& 4 richer, run them the same, or run 4 richer, depending on what is best for your bike. Without a dyno, and the ability to differentiate, I would go with what works in 95%, and that is 1& 4 one step richer.
In the srad case, it is mostly influenced by heat, although airbox dynamics has some affect.
Intestingly, the zx6/7/9's were mostly the opposite, with inner cylinders jetted richer, although the zx9 switched back and forth a few times.
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1996 GSXR 750 EX AMA, Carillo, Yoshimura, Kit airbox, Keihin FCR39, Fox, Brembo, Hindle, total loss and starter less ignition, Graves, Vortex
Oh, well, your other question about the needle and fuel level and why they are not altered with staggered main jets:
The biggest reasons the needles are usually not different from inner to outer is that an incredible amount of time goes into (went into... All this happened a long time ago) needle testing. Marc used to spend unreal time on some bikes getting just the right needle profile : length, point of origination of taper, root diameter, etc. And, after all, the main jet has effect on the entire rpm band, the needle primarily 4-7k.
The were situations where testing warranted staggered needles, for maximum performance, usually accompanied by enlarging main air jets (also in staggered fashion)........ Those were/are the 1.7 Race Kit, (like the set I am sending you Armi).
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1996 GSXR 750 EX AMA, Carillo, Yoshimura, Kit airbox, Keihin FCR39, Fox, Brembo, Hindle, total loss and starter less ignition, Graves, Vortex
perhaps I'll video the tune the way it is, even all the way across, then maybe some you guys with the experience can tell me whether or not its good or if it can be better, I have nothing to compare it to other than FI bikes as this is my first SRAD so I don't really know if its running good or if it can run better?
it definately pulls like a raped ape up top like around 10-12 , it literally buries the needle rat 16k, seems like there is no rev limiter at all just rushes up and pins the needle, is that normal behavior?
I got the floats set and the carbs synced today, haven' gotten to test ride yet but it seems to idle, start and rev better. It still hangs at 3k when I let off the throttle, what size pilot jets do you recommend ccm?
Odd thing is, I just checked my old carbs and they had 12.5 as well and I never had the rpm hang with them. But then again they had cracked diaphragm and other issues. I think the main jets may have been richer as well
The bike still isnt running bet well, it sounds like a quad. Timing is on and when I pulled the plugs after I test rode it the center 2 were darker but looked alright, but the outer too look like it is running far too lean. When the carbs are removed there is smoke coming out of the outer 2 cylinders. Floats are set at what I believe to be 8mm, the main jet stagger is correct and the mixture screws are set at 2 turns out. Any ideas what is going on here?
Well, 2 turns out is pretty lean, what are the rest of your settings?
You followed my thread and measured float height with spring UNCOMPRESSED!
Stagger is correct?
List:
Pilot jet
Pilot fuel screws
Pilot Air jet
Float heights
Jet needle clip positions
Main jets
Main air jets (if drilled)
Anything else related
Compression?
Pilot Jet- 12.5
Pilot Fuel Screws- Can't find a number, set two turns back.
Pilot Air Jets- 27.5
Float Heights- 8mm (I think)
Jet Needle Clip Position- 3rd
Main Jets- 132.5 130 130 132.5
Main Air Jets- Not sure which one this is.
Have not checked compression will try and check tomorrow since it is my day off. Which way do the pilot screws have to be turned to richen the mixture.
Linear Mode
