too rich, or too lean?

csr 1000 with k&n pods and v&h 4 into 1.cv34 carbs. went up one on the pilot to 40 and bought 127.5 and 130 for the mains. Just got the header and figured I needed to adjust the jets. I went up two and used the 130's for mains and the bike started breaking up between 1/2 and 3/4 throttle (about 4500-5000 rpm's) I wanted to start rich so I didn't pop the engine. went down to 127.5 and same thing but not as bad. then found the pilot screws (or air/fuel screws) to be out more than 4 turns. left the 127.5's in and adjusted the screw back to 2 turns and same thing, continuing to get better. then back to the stock jets and went up and down with the fuel/air screws in slow increments. ( I changed the plugs twice throughout this and found the middle 2 cylinders to be running richer than the outer 2, the outer 2 looked like they were burning perfectly) the last move was to adjust the fuel/air screws leaner on the middle 2 cylinders with the stock jets and this has been the closest to running correctly. My question is is that I figure the bike would be rich with the 130's and lean with the stock 122.5's, and that the bike would run differently being rich than running lean, so why the hell does the bike seem to be running very simmilarly when it is supposedly rich or lean? (with the main jets)

In my experience when a bike is lean it will spit, sputter, surge, just all kinds of stuff when you give it gas, but when it's rich it will just fall on it's face. Most guys call it a blubber, I can best describe it as when you twist the throttle, nothing happens.

Right out of the Keihin CR T-Shoot guide.... Applies to pretty much the same for all mechanical carbs...

first of all thanks guys and I will use your info for sure. (one of you guys mentioned that pretty much all mechanical carbs are the same, well the cv34 carbs are considered a vacuum type carb, I guess they are mechanincal in that they have the same components as all the rest, and thats probably what you meant) I forgot to mention that due to the stupid factory design on the original petcock on my bike I had to put in an in-line shut off. When the carbs stop sucking fuel from the tank there is a vacuum line from the carbs to the petcock that are supposed to allow a rubber diaphragm to close and fuel to stop flowing. The diaphragm stopped functioning and just allowed fuel to run out of the carbs. The rebuild kit was too expensive at the time. I will be replacing it with a totally mechanical petcock. Long story short, the line loops a bit and there is a restriction due to the valve and the hose going from that valve to the carbs is smaller than stock. So I need to first eliminate the possibility of the carbs starving for gas, and then I can start with the "normal" adjustments. P.S. when I change to a mechanical petcock should I just plug the vacuum line from the carbs to the petcock? or let it run freely?

nedrowjoe wrote: ...when I change to a mechanical petcock should I just plug the vacuum line from the carbs to the petcock? or let it run freely?

Would remove the vacuum line and plug (cap) the unused vacuum nipple.

Good Fortune!

When your jetting is too rich your engine will rev slowly and the top end will feel "flat" sometimes the peak rpm's will also slowly decrease.

When you are jetted too lean, you will feel the engine rev clean, then start to studder. You also might hear some poping from the exhaust when you let off the gas.

A WO "throttle chop" plug reading is a good method to get an idea of how you are jetted.

so I am so frustrated with this F*#&@*g thing, Another day of carb adjustments, to no evail. I eliminated fuel starvation as an issue by replacing the petcock. Now I need a new starter from all this messing around. I don't understand how the bike was running so clean with the stock exhaust and I put a header on an a whole shit ton of issues start showing up. so I now know it has nothing to do with the jet needle clip position, It ran terrible after I shimmed it(only 1 mm). I'll be going back to stock setting on that one. actually tmrw I think I'll be setting everything back to stock putting it together and seeing what happens. I'll prob be starting with the original issue I posted about. the bike runs perfect, I mean perfect until I get on the throttle about 4500 RPM's, she start getting choppy and sounds like my old 2 stroke suzuki RM 125 when I had a fouled plug. From what polar is saying it sounds like I'm too lean. I know this because I went all the way up to 3 sizes bigger than stock and It did the same thing. But I'm not I have no Idea, this is my cry for help before I take the biggest hammer I can find and really fix the problem. But then I wouldn't be able to be a member here, and I love my bike so any ideas?

I would suggest you find the proper main jet first. You want to get the best / most top end power - above about 7500 rpm. If it pulls harder when cold than when hot then the main is too large. If it does not pull well when cold and only gets a little better when hot the main is too small. You want the main that will pull the hardest when the bike is warm.

Once you have found the correct main then move to the mid range (needle).If the engine pulls better or is smoother at full throttle/5k-7k in a full throttle roll-on starting at <3k when cool but soft and/or rough when at full operating temperature, it is too rich in the midrange and the needle should be lowered. If the engine pulls better when fully warmed up but still not great between 5k-7k, try raising the needle to richen. If it pulls equal cold or hot the needle is most likely in the correct position.

Once you have set the mid range move on to the low end via bowl fuel levels. To get best low-end power, set float height (fuel level) so that the engine will accept full throttle, without missing or stumbling, in 2nd gear from 2.5k to 3k rpm at minimum. Since the main jet WILL affect low speed operation, the MAIN JET has to be within 1 or 2 sizes of correct before final float setting. If the engine is left with the fuel level too high, the engine may foul plugs on the street and will be "soft" and boggy at part throttle operation. Adjust Floats to raise/ lower the Fuel Level. The Fuel level height in the float bowl affects full throttle/low rpm and, also, richness or leanness at cruise/low rpm. If the bike that runs cleanly at small throttle openings when cold, but starts to show signs of richness as it heats up to full operating temperature, can usually be leaned out enough to be correct if the fuel level is LOWERED 1mm.

Then move on to idle and low rpm cruise. Set for smoothest idle and 2nd gear, 4k rpm, steady state cruise operation. Set mixture screws at recommended settings, as a starting point. For smoothest idle, 2nd gear 4000 rpm steady state cruise , and 1/8 throttle high rpm operation.Pilot fuel mixture screw settings, float level and pilot jet size are the primary sources of mixture delivery during 4000 rpm steady state cruise operation. If lean surging is encountered, richen mixture screws (turn out) in 1/2 turn increments.Pilot fuel mixture screw settings, float level and pilot jet size also affect high-rpm, 0 to 1/8 throttle maneuvers. Too lean, will cause surging problems when the engine is operated at high rpm at small throttle openings! Opening the mixture screws and/or increasing pilot jet size will usually cure the problem. A rich problem gets worse as the engine heats up.
If the throttle is lightly "blipped" at idle, and the rpm drops below the set idle speed, then rises up to the set idle speed, the low speed mixture screws are probably set too rich: try 1/2 turn in, to lean the idle mixture. A lean problem gets better as the engine heats up.
If the throttle is lightly "blipped" at idle, and the rpm "hangs up" before dropping to the set idle speed, the mixture screws are probably too lean: try 1/2 turn out, to richen mixture.

thanks for all the help guys, I GOT IT!!!! :woohoo: , and as far as the last post thanks, I'll be using that to fine tune her. I'm glad I got it running clean, because I promised myself I was going to do everything on this bike myself, and so far everything has turned out great, granted it's been taking longer than I'd want it to.

Oh and by the way I am embarassed to say what I'm pretty sure the problem was. when I changed the pilot jet I took off those little plugs that cap them and someone told me kawi put those in as an anti tamper device and that I didn't need them. wrong, you need them! I cleaned them really well again and took out the shims on the needles that were way too rich.