need CV carb exPERT

[nert]

Road_Clam
I can do that. I have a very good infared temp gun.
Thanks. I am curious to see the results.
vic

[KEITH KRAUSE]

As for your mixture screw question, if the pilot circuit is clean/correct jet size/correct float level, turning the screw out will have a normal effect and allow more mixture. As for if the pilot circuit is to blame, there is an overlap of the pilot and jet needle circuits at the throttle positions you say the problem presents itself. Mostly the jet needle in my opinion.
What I find interesting is you previously said to get a good idle you must set the mixture screws to 1/2 turn out. Anything else and idle quality suffers. You now have them set at 2 turns out (which is much closer to normal) and performance has improved. The bike is idling well at 950 rpm's. Unless you made some change we don't know about, what do you think has happened here that the bike now accepts the screws at 2 turns out?

[nert]

Curious minds think alike. When i lowered the fuel level I did not readjust the pilot screw, until readings your posts. Last night, prior to going home, as a test, I turned in each pilot screw a half turn from the 2 turns I had set the night before. I began my trek home in 58? ambient temp. I neglected to readjust the idle speed since I made the adjustment engine off. I have a Jammer with lowers and I would have to remove the lowers to get to the idle speed. Didn?t think a half turn would make that much difference. But, on the road, idle speed was = or < 700 and poor. Engine ran a bit ragged at lower RPM. Didn?t seem to have as much low end torque either, and initial opening of the throttle would stumble. Higher RPM and greater throttle seemed fine. At the end of 30 miles, idle RPM picked up about 150 which is what I would expect from an initial lean setting and with the engine fully warm. While the engine was still hot, I then readjusted each pilot screw for best idle quality and highest RPM. And as you might guess, I did have to turn them out. I did not ride today as the forecast is for rain. But I am expecting good results once I am back in the saddle. The only thing I didn?t like, is pilot screw #2 did very little to fault idle speed or quality. Something I still need to check.

Aren?t you a even a bit curious about my Sync screw modification, or am I the only one that finds you have to ?compensate? the setting before tightening the jam nut.

Thanks again
vic

[Joe Nardy]

Curious minds think alike. When i lowered the fuel level I did not readjust the pilot screw, until readings your posts. Last night, prior to going home, as a test, I turned in each pilot screw a half turn from the 2 turns I had set the night before. I began my trek home in 58? ambient temp. I neglected to readjust the idle speed since I made the adjustment engine off. I have a Jammer with lowers and I would have to remove the lowers to get to the idle speed. Didn?t think a half turn would make that much difference. But, on the road, idle speed was = or < 700 and poor. Engine ran a bit ragged at lower RPM. Didn?t seem to have as much low end torque either, and initial opening of the throttle would stumble. Higher RPM and greater throttle seemed fine. At the end of 30 miles, idle RPM picked up about 150 which is what I would expect from an initial lean setting and with the engine fully warm. While the engine was still hot, I then readjusted each pilot screw for best idle quality and highest RPM. And as you might guess, I did have to turn them out. I did not ride today as the forecast is for rain. But I am expecting good results once I am back in the saddle. The only thing I didn?t like, is pilot screw #2 did very little to fault idle speed or quality. Something I still need to check.

Aren?t you a even a bit curious about my Sync screw modification, or am I the only one that finds you have to ?compensate? the setting before tightening the jam nut.

Thanks again
vic

Vic,

First, yes I do have problems with the screw and locknut sync adjustment. I would be very interested in your sync screw modification.

Second, I haven't read this thread thoroughly but has anyone mentioned raising or lowering the needles? My GS1100E always had a lean issue at steady throttle, most noticeable at around 3200 RPM. The condition got much worse when I installed a Stage III K&N jet kit with the stock settings. Each time I raised the needles the problem got better until I got to the highest setting which is just about right. I had a similar situation with an '88 Honda Hurricane 1000 that was resolved the same way.

Thanks,
Joe

[nert]

The CV carbs don't have adjustable needle positions.
I will try to figure out how to post photos and text for the carb mod, or i can assemble a .pdf and email to you.

[Joe Nardy]

The CV carbs don't have adjustable needle positions.
I will try to figure out how to post photos and text for the carb mod, or i can assemble a .pdf and email to you.

I think you can raise the needles by shimming them with washers. I don't know how you'd lower them.

If you need somewhere to post pictures I can do that. You need a web host that allows linking to pictures. I think Photobucket does and it is free.

Thanks,
Joe

[KEITH KRAUSE]

Joe, I didn't mention raising the jet needles because his bike is totally stock except for the K&N filter. Usually richer mixture screw settings will work well enough. But since his bike has always done this since he got it, it's always possible a jet needle change could help things. I did mention his problem is where the pilot circuit and jet needle circuit overlap and both/either could be causing his problem.
I was a little curious too about his throttle adjuster mod' but was concentrating on his problem. I've never really had a problem with losing my setting while torquing the holder nuts. Sure, I have a little trouble at times. I just follow the factory torque setting, which is generally 3-4 ft/lb. Over-tightening them is where you have problems.

[Road_Clam]

As for your mixture screw question, if the pilot circuit is clean/correct jet size/correct float level, turning the screw out will have a normal effect and allow more mixture. As for if the pilot circuit is to blame, there is an overlap of the pilot and jet needle circuits at the throttle positions you say the problem presents itself. Mostly the jet needle in my opinion.
What I find interesting is you previously said to get a good idle you must set the mixture screws to 1/2 turn out. Anything else and idle quality suffers. You now have them set at 2 turns out (which is much closer to normal) and performance has improved. The bike is idling well at 950 rpm's. Unless you made some change we don't know about, what do you think has happened here that the bike now accepts the screws at 2 turns out?

air screw adjustment vs. pilot jet size needs to be "in sych" with each other also. Where the Mikuni BS mixture screws meter fuel flow, the generall rule of thumb is if you need to adjust the mixture screw less then 1 turn, you need a leaner pilot jet. If you need to adjust the mixture screw beyond 2.5 turns you need a richer pilot jet. Basically mixture screw adjustment between 1 and 2.5 turns out, is a good sign you have chosen the correct size pilot jet. Every bike will run a little different, based upon many variables, ie. humidity, ambient air temps, mods, and so on.
Rich

[toymechanic.]

nert wrote:I Sync the carbs (1) a year, begining the start of spring riding season. I have a Morgan CarbTune. The most difficult part of the sync is the set screw and lock nut, as it it easy to foul the setting once the lock nut is tighten. I have developed a pretty simple carburetor modification to provide tension to the Synchronizer screw, eliminating the jam nut for the Synchronizer screw. Adjustment is performed more easily and more accuratly. I have retested the sync to be sure my design has held up. ( i am most happy with the results). I have modified several carb sets on other Mikuni banks with successful results.

Would you care to share to mod's you made, because I hate the lock nuts as well. I was thinking about using a teflon inserted set screw.

Also to answer a question that I don't think was answered. The fuel/air mixture screw uses more fuel the farther out it is. Secondly the fuel level high or low will not effect the fuel/air mixture screw circuit, unless the float level is way to high or way to low. Also if your carbs have those little black plugs, they need to sealing properly or they will effect the f/a circuit big time.

Lastly post the mod's, because allot of us have inquiring minds.

[nert]

HEY, you have the same bike i have!! mine is the blue

http://www.factorypro.com/tech/carbtune,CV,high_rpm_engines.html

According to the CV Carb Tuning papers i have. Fuel level, even within range will make a very big differance in performance. And i can say, without reserve, it does. The little black plugs are new and seal well.

Thank you for the answer on the pilot screw question.

Yes, i would like to share the mod. I put together a .pdf with directions and photos. Don't know how to make available other then send by email.

[KEITH KRAUSE]

I answered your question earlier about the mixture screw and how to adjust it richer/leaner.
Also, road_clam has the "rule of thumb" regarding mixture screws reversed.
It's true the basic range of adjustment should be around 1 to 2 1/2 turns, but if best idle is achieved at less than 1 turn, this suggests you need a larger pilot jet or the fuel supply portion of the pilot jet circuit is clogged somewhere. If best idle is achieved beyond 2 1/2-3 turns, this suggests the pilot jet is too rich or the air supply portion of the pilot circuit is clogged somewhere.
You can visit the Mikuni carb tuning site, such as their HSR section, or K&N's site. They'll tell you the same thing.

[Road_Clam]

I answered your question earlier about the mixture screw and how to adjust it richer/leaner.
Also, road_clam has the "rule of thumb" regarding mixture screws reversed.
It's true the basic range of adjustment should be around 1 to 2 1/2 turns, but if best idle is achieved at less than 1 turn, this suggests you need a larger pilot jet or the fuel supply portion of the pilot jet circuit is clogged somewhere. If best idle is achieved beyond 2 1/2-3 turns, this suggests the pilot jet is too rich or the air supply portion of the pilot circuit is clogged somewhere.
You can visit the Mikuni carb tuning site, such as their HSR section, or K&N's site. They'll tell you the same thing.

OK, not to start arguing, but I am confused. The BS mixture screw meters fuel. Turning in the mixture screw CW, is effectively leaning the idle circut, correct?(or do I have this specific comment backwards?)

[nert]

As for your mixture screw question, if the pilot circuit is clean/correct jet size/correct float level, turning the screw out will have a normal effect and allow more mixture.

I did read your answer, i was being courteous to "toymechanic." But after reading your last post, i am confused as well since.

less than 1 turn, this suggests you need a larger pilot jet or the fuel supply portion of the pilot jet circuit is clogged somewhere. If best idle is achieved beyond 2 1/2-3 turns, this suggests the pilot jet is too rich or the air supply portion of the pilot circuit is clogged somewhere.

that appears to be contradictory, but at this point i have to accept it on faith.
after more thought!!! I think i got it. IF the fuel portion is clogged, then as the screw is turned out, it only allows more air in (not fuel) and the mixture ends up lean so the screw is turned in for better idle quality by mixing the restricted amount of fuel in correct balance with the air that can still be metered by the screw. Correct? Or am i still confused?

[KEITH KRAUSE]

I answered your question earlier about the mixture screw and how to adjust it richer/leaner.
Also, road_clam has the "rule of thumb" regarding mixture screws reversed.
It's true the basic range of adjustment should be around 1 to 2 1/2 turns, but if best idle is achieved at less than 1 turn, this suggests you need a larger pilot jet or the fuel supply portion of the pilot jet circuit is clogged somewhere. If best idle is achieved beyond 2 1/2-3 turns, this suggests the pilot jet is too rich or the air supply portion of the pilot circuit is clogged somewhere.
You can visit the Mikuni carb tuning site, such as their HSR section, or K&N's site. They'll tell you the same thing.

OK, not to start arguing, but I am confused. The BS mixture screw meters fuel. Turning in the mixture screw CW, is effectively leaning the idle circut, correct?(or do I have this specific comment backwards?)

Turning in the mixture screw on a CV carb does effectively lean the circuit, in a CORRECTLY operating, correctly jetted pilot circuit. But, the mixture screw also meters air, not just fuel. The operation of the screw can actually give reversed results from what's expected if the pilot circuit has a blockage of air or fuel. A "blockage" can also include a too small jet, or poor vacuum. A too large jet will also reverse the expected operation of the screw.
I'm not arguing either. See? Lots of smilies. I just share my experience/opinions, but mostly experience. Just because I say or read something, doesn't make it fact. I suggest asking Mikuni or K&N or one of the better jetting/tuning sites if you need more info. They can explain better or more clearly than me?

[KEITH KRAUSE]

nert, the last part of your last post is a good scenario.
The thing here is a CORRECTLY operating, correctly jetted pilot circuit will allow the mixture screw to operate in its designed and expected way.
If anything causes a lack of fuel or air, or an unequal abundance of fuel or air, the screws operation will not be normal or as expected.