4-1 w/stock air box?

[badbrown]

Currently I'm running the stock air box w/no top and a UNI filter with the MAC 4-1. I'm trying to correct the lean condition caused by the pipe. Will I get away with this by using larger mains and adjustment/testing procedures since the DJ kit is not available. Not looking for huge HP just smooth operation. Idle is smooth and pulls hard to 5K. But weakens after 5K. In the middle of determining throttle position. The lean plug color is what concerns me the most. I figure the pods would be a mistake in this case making it more lean although I do have them. Going to try a couple more things tommorrow.

[brveagle]

Yeah, bump up your mains a little bit and you're bike will really apprecaite it.

The fact that it idles good is a good sign that a little tweaking is all that is necessary

[rapidray]

First, drill out the plugs covering the mixture screws if you haven't yet. Second, you will MOST likely need to shim the needles some since you can't get adjustable needles from Dynojet. Third, go up about 3-4 sizes on the main jet for a START point. Last, call Mark at Factory to see if he has needles you can use. He KNOWS what he is doing & chances are he will have some that will work. Call him at 415-721-4964. Let me know what you end up doing. Ray.

[brveagle]

First, drill out the plugs covering the mixture screws if you haven't yet. Second, you will MOST likely need to shim the needles some since you can't get adjustable needles from Dynojet. Third, go up about 3-4 sizes on the main jet for a START point. Last, call Mark at Factory to see if he has needles you can use. He KNOWS what he is doing & chances are he will have some that will work. Call him at 415-721-4964. Let me know what you end up doing. Ray.

He shouldn't have to shim the needles if he goes up in sizes of the main jet. Shimming the needles is his last worry as that will come with the fine tuning part.

Stock needles are okay.

[badbrown]

Cool thanks for all the help. Did the adjustments today and cleaned jets and holes again for good luck. Got them bench sinked and idle set. I moved the needle one richer also and my mains were bored out manually from 80 to @100. I went touroughly over the intakes and boots on air box for leaks. That should cover it. Valves were adjusted and I have DYNA S and 2004 Katana coils. Now vac sinc plug chop test and road test. Phheeew. Hopefully I got my midrange back.

[KEITH KRAUSE]

He shouldn't have to shim the needles if he goes up in sizes of the main jet. Shimming the needles is his last worry as that will come with the fine tuning part.

Both jet needle and main jets will need to be richened, along with the pilot circuit. The jet needle and main control separate throttle positions, as does the pilot circuit.
badbrown, though the pipe will lean you out some, the biggest change effecting mixture is the air box top being removed.

[rapidray]

Keith is right, the air box lid is the biggest factor. BRVEAGLE, you are wrong because he WILL have to move the needles to get it to run cleanly in the midrange. Sorry to say you're wrong but I have been doing this for MANY years & I know what I'm talking about. If you want to challenge yourself sometime eagle, pull an air box off of something & get the bike to run correctly withOUT buying a jet kit! Ray.

[brveagle]

Keith is right, the air box lid is the biggest factor. BRVEAGLE, you are wrong because he WILL have to move the needles to get it to run cleanly in the midrange. Sorry to say you're wrong but I have been doing this for MANY years & I know what I'm talking about. If you want to challenge yourself sometime eagle, pull an air box off of something & get the bike to run correctly withOUT buying a jet kit! Ray.

Well Sir, With all due respect, i also know what i am talking about. The case in point here would be my own personal experience in jetting my 550. I have had to rejet my bike each time i bored it out and am now in the process of fine tuning downlow. I run the stock airbox, with a K&N drop in, and no airbox lid along with a V&H 4-1. At first i tried shimming the needle to correct the lean condition, but found that to be useless. What does work however is to raise the size of the mains. Yes, fine tuning can be achieved with the use of an adjustable needle, but more often than not, it doesn't matter.

Yes i'm saying that adjustable needles can be helpful, but it's the mains that need to be changed, the needles just work off the increased needle size.

[badbrown]

Thanks for all of the info. Haven't tested because of rain the last two days. But I will consider all of of the options presented. I'm alot closer than I was...........and I learned ten times more about carbs this week alone than in my whole life. All thats left to do is test.....Side note...This tuning is for the VM carbs.. But I also have another 550e with the CV carbs that I'll be tearing in to soon. I may run a open stock exhaust on that one with the stock air box.

[GS Farmer]

I'm with Ray and Keith, based on experience of rejetting three GS's in the 80's and one in process as we speak, I have ALWAYS had adjust the needles to get it spot on. Not saying that you didn't get yours right, with mains only, but based on my experience, you are definitely the exception and not the rule. The washers from radio shack, work well with the non-ajustable needles. Good Luck!!

[byrdman76]

from one 550 owner to another

Bad brown -

Before you get started on the carbs have you adjusted the valves yet?

below is the set up that i am currently running on my 550 with VM22 carbs. I run cheap K&N knock off pods and a gutted stock exauhst system. My bike pulls like a train to redline with no flat spots or any signs of weakness (for a 28yr old 550 that is :-D). Dont fall into all the hype about the issues with removing the airbox. This actually seems to be an impovement for the VM carbs - the CV's may be a little tempermental. Rip the carbs completely down including the fuel pilot adjustment screws - this is very important. Make sure to "dip" the carbs in berrymanns carb dip over night and thouroughly clean and clear all pasages with compressed air and carb fluid after dipping them. Get the rebuild kits ("keyster" had some nice kits), jet kits, and pods off ebay. Reassmeble using these settings. I set the carbs up with 100 mains (ebay 32 jets for about 30 bucks), stock pilot jets - try and save the originals, set the pilot fuel screws 2 turns out, air screw mixture 2 turns out, standard float height, and highest needle position for the slides. bench sync the slide height before reinstalling the carbs. Once you get the bike dialed in using the highest RPM method, get a set of cheap mercury carb sticks and and fine tune the slides. Once this has been completed adjust the airscrews one last time using the highest rpm methind.


One more thing - the Dyna S ignition/coils/ and wires are some of the best mods I have done to this bike. If you can justify the cost I would definetly recommend it. Z1 enterprises is a great resource for ignition components.

Good Luck!

[KEITH KRAUSE]

Well Sir, With all due respect, i also know what i am talking about. The case in point here would be my own personal experience in jetting my 550. I have had to rejet my bike each time i bored it out and am now in the process of fine tuning downlow. I run the stock airbox, with a K&N drop in, and no airbox lid along with a V&H 4-1. At first i tried shimming the needle to correct the lean condition, but found that to be useless. What does work however is to raise the size of the mains. Yes, fine tuning can be achieved with the use of an adjustable needle, but more often than not, it doesn't matter.

Yes i'm saying that adjustable needles can be helpful, but it's the mains that need to be changed, the needles just work off the increased needle size.

No arguing here, just stating facts that I've always tried to make others aware of.
These VM carbs have a pilot circuit that transitions to the cut-away that transitions to the jet needle that transitions to the main jet. There is some overlap obviously as each circuit gives regulation over to the next circuit. It's all about throttle position. Each circuit regulates during a certain range of throttle opening. The SMALLEST opening in ANY circuit will determine/regulate fuel flow.
All throttle positions are approximate and keep in mind that as the throttle continues to open, the previous circuits influence tapers off as the next circuit takes over, which is the overlap.
At closed throttle/idle, the pilot jet regulates. It continues to until 1/5 throttle where the cut-away regulates. The jet needle takes over at 1/4 throttle. As the throttle is opened, the tapered needle rises up through the needle jet which is fed by the main jet screwed into its bottom. A large portion of the jet needle actually leaves the needle jet as the throttle is opened further. At 1/4 throttle, the main jet opening is larger than the space between the jet needle and needle jet, and so, the jet needle will regulate flow. As the tapered jet needle rises up and out of the needle jet, the space between the jet needle and needle jet continues to widen. At 3/4 throttle, the jet needle rises to the point that only the smaller tapered portion is still fully inside the needle jet, and so, the space between the jet needle and needle jet has now widened to the point that it is now a larger opening than the main jet. Since the SMALLEST opening will regulate fuel flow, the main jet takes over completely all the way to full throttle.
That's the way the VM carbs are designed and that's how the various circuits regulate. The jet needle position is extremely important to all throttle positions from approx' 1/4 to 3/4 and has some significant effect before 1/4 actually, especially with a freer flowing intake/exhaust. The main jet has absolutely nothing to do with performance other than the throttle positions it's intended to regulate (3/4 to full). A VM equipped bike would run perfectly at 1/3 throttle with the main jet removed actually.

[KEITH KRAUSE]

Bad brown -

Before you get started on the carbs have you adjusted the valves yet?

below is the set up that i am currently running on my 550 with VM22 carbs. I run cheap K&N knock off pods and a gutted stock exauhst system. My bike pulls like a train to redline with no flat spots or any signs of weakness (for a 28yr old 550 that is :-D). Dont fall into all the hype about the issues with removing the airbox. This actually seems to be an impovement for the VM carbs - the CV's may be a little tempermental. Rip the carbs completely down including the fuel pilot adjustment screws - this is very important. Make sure to "dip" the carbs in berrymanns carb dip over night and thouroughly clean and clear all pasages with compressed air and carb fluid after dipping them. Get the rebuild kits ("keyster" had some nice kits), jet kits, and pods off ebay. Reassmeble using these settings. I set the carbs up with 100 mains (ebay 32 jets for about 30 bucks), stock pilot jets - try and save the originals, set the pilot fuel screws 2 turns out, air screw mixture 2 turns out, standard float height, and highest needle position for the slides. bench sync the slide height before reinstalling the carbs. Once you get the bike dialed in using the highest RPM method, get a set of cheap mercury carb sticks and and fine tune the slides. Once this has been completed adjust the airscrews one last time using the highest rpm methind.


One more thing - the Dyna S ignition/coils/ and wires are some of the best mods I have done to this bike. If you can justify the cost I would definetly recommend it. Z1 enterprises is a great resource for ignition components.

Good Luck!

byrdman, you never got back to me to say how the suggested jetting worked out on your bike. I just like to know because it helps others. I make educated guesses but they are still guesses. But I can see you followed my suggestions and it appears to be running well.....and on the first try!
That's why I take the time to help with this carb stuff. So you can get to riding instead of wrenching.
'Scuz me for tootin' my own horn.

[49er]

I'm with Ray and Keith, based on experience of rejetting three GS's in the 80's and one in process as we speak, I have ALWAYS had adjust the needles to get it spot on. Not saying that you didn't get yours right, with mains only, but based on my experience, you are definitely the exception and not the rule. The washers from radio shack, work well with the non-ajustable needles. Good Luck!!

Hey guys, there's one thing that has not been considered here. Are we talking stock needles or aftermarket ones that a PO may have played with, unsucessfully?
Example, if the stock 550 has a relatively shallow tapper and large diameter, it will be more benificial to increase the main jet size than shim the needle, for a given response in midrange and the top end. If however the needle has a steeper taper and smaller diameter, the better method may be to adjust the needle height.
So depending on the situation, there could be merit to both solutions.
If it's running well at idle and up to 5000rpm, the open airbox isn't causing leanness where it should be noticed most.

[KEITH KRAUSE]

Different needle tapers will change things a little. A more aggressively tapered needle will come into effect sooner than the factory needle. But my transition description above holds true for all jet needles.
You don't change main jets for a 1/4 to 3/4 throttle issue. You adjust the needle.