2004 With Modified Stock Exhaust

[Johnc1go]

I had the bike dyno'd last summer. This chart shows the A/F ratio on the right side. Since this chart was created, I've swapped out the stock pipes for Marks 4/2. I haven't yet had it checked, but guess from what I read here, that I"m running a little rich. The exhaust tone at highway speeds sounds sort of "burbly" or "full" or even kinda like a wet fart. That's the best I can describe it. I'm told that the needles need to be shimmed, but I don't understand where to locate the washer on the needle assembly for it to be right.

 

[SpecOps13]

Shimming the needle will make the mid range richer... The spacer (shown in the picture) has a tiny pin thst sticks out of it. That must be aligned and in the tiny hole in the slide for proper reassembly....




Mine with Mark's 4-2 at sea level: 152.5 mains (stock), stock needles shimmed 0.028, Air Fuel Screws 3-1/4 turns out... all other jets are stock...

 

[KJShover]

guess from what I read here, that I"m running a little rich. The exhaust tone at highway speeds sounds sort of "burbly" or "full" or even kinda like a wet fart. That's the best I can describe it. I'm told that the needles need to be shimmed, but I don't understand where to locate the washer on the needle assembly for it to be right.

Not to shabby of numbers for a stocker.

If your running rich, shimming the needles can make it worse. If your running stock mains, I'd drop to a 150 mikuni, main.
See how it runs, you can always shim from there.

Your only about 300' higher elev than me. I ran (still am) a Kerker. Without a jet kit I was shimmed, 150 mains and around 3 on the a/f. I got 40+ on the hwy and 35-38mpg around town.

I'm now running a morley jet kit w/stage 7 needles and couln't be happier with the performance and milage.

 

[Johnc1go]

I think I get it now. The needle remains stationary relative to the diaphragm, but the diaphragm moves in and out as the rider changes throttle position. I'm guessing that when throttle is applied, that the diaphragms move inward causing the needle to move inward as well, right? By shimming the needle, it cannot go in as far as in the stock condition, so more fuel can flow, right? See, my problem is that I don't feel comfortable messing with my carbs until I understand how they work. According to the dyno chart, it appears that the carbs went rich at the midrange and most likely the Mark's pipes may have made it richer yet.

If I'm understanding the information you both put up, then I think the correct course of action would be to adjust the A/F screws and leave the needles alone for now until I can get it back on a dyno.

As a sidenote, KJShover, I'm not convinced that my bike is making as much HP as the chart says, it was a portable dyno and it could have been out of calibration or set up to show higher than normal readings just to make people feel good. I will get it confirmed at a place that has a fixed dyno. Specops13 great picture, I have it downloaded and in my vmax folder.

 

[06VMAXIMUS]

The needle does stay stationary in the slide, but the diaphram pulls it outward, not in. Shimming the needle richens the midrange.

 

[Johnc1go]

I looked at my dyno chart wrong, it's showing lean in the midrange and rich from 6g to redline. Ok, so needle shims richen midrange, I understand now. Do the A/F needles control airflow or fuel flow? I don't mean to be a hemorroid, I just don't want to mess up my bike by having the mixture wrong.

 

[Rusty McNeil]

Hey John,

Do a search for Factory Pro CV tuning (these are CV carbs) and read the high RPM guide, it'll be a good place to start to getting an understanding of these carbs and "what does what".....After that go to our Carb section and browse around and you'll learn plenty just browsing.......

If all else fails you can Call Mark at 3 am on a Sunday Morning and ask him any questions you still have:rofl_200::rofl_200:

 

[KJShover]

Here is a good chart of what does what. If you want to get a hold of Mark, don't just call at 3am all willy nilly. You have to call using the Vmaxforum "code"
It's pretty simple; start calling at 1am, let it ring 2 times, then hang up.
Repeat this every 20 mins. Then at 2 am, call and let it ring 1 time. repeat this every 10 mins. Then when you call at 3am, just let it ring until someone answers :rofl_200:

 

[[email protected]]

Do the A/F needles control airflow or fuel flow? I don't mean to be a hemorroid, I just don't want to mess up my bike by having the mixture wrong.

A/F screws control fuel. Loosening the screws, (counter clockwise) richens the mixture.

 

[Rusty McNeil]

Here is a good chart of what does what. If you want to get a hold of Mark, don't just call at 3am all willy nilly. You have to call using the Vmaxforum "code"
It's pretty simple; start calling at 1am, let it ring 2 times, then hang up.
Repeat this every 20 mins. Then at 2 am, call and let it ring 1 time. repeat this every 10 mins. Then when you call at 3am, just let it ring until someone answers :rofl_200:T

I cannot stop laughing:rofl_200::rofl_200:

 

[VMax-Mike]

I have drilled out stock exhaust and bike runs good but i had a popping noise out the exhaust at 4000rpms in 4th gear. I talked with ufo and he said to trick the vboost servo and see what it dos. bike seems to run great but i had to bump my idle up to 1000rpms or it would stall. and i could not get any adjustment from my idle air scews. I put them at 1 1/2 turns out. I have never adjusted multiple carbs I know when i adjust one carb as i turn the srew in the motor starts to die and than when i back it out the motor rpms go higher and higher than it starts to die again and than i turn it in 1/4 turn and set idle, as long as im not more than 3 turns out. the only change i get with multi carbs when i turn the screw in or out is the bike dies. Dos this mean i need to go up in my jet size. Or do i need to follow a different procedure for multi carbs.

 

[KJShover]

1000 rpms isn't out of the range.

To set your a/f screws:
Go to each carb, Then, one at a time, turn in the a/f screw in until the engine almost dies. Then back the a/f screw out until the engine recovers, then turn out another 1/4-1/2. Move on to the next carb and repeat until all carbs are done.
Set RPM between 800-1000

 

[alorio1]

Here is a thread with members carb set-up and what exhaust system they have.....very interesting what is working for others, you must pay attention to their elevation it makes a difference.

http://www.vmaxforum.net/showthread.php?t=16981&highlight=post

 

[06VMAXIMUS]

Don't forget to sync the carbs, or you will be chasing your tail!

I have drilled out stock exhaust and bike runs good but i had a popping noise out the exhaust at 4000rpms in 4th gear. I talked with ufo and he said to trick the vboost servo and see what it dos. bike seems to run great but i had to bump my idle up to 1000rpms or it would stall. and i could not get any adjustment from my idle air scews. I put them at 1 1/2 turns out. I have never adjusted multiple carbs I know when i adjust one carb as i turn the srew in the motor starts to die and than when i back it out the motor rpms go higher and higher than it starts to die again and than i turn it in 1/4 turn and set idle, as long as im not more than 3 turns out. the only change i get with multi carbs when i turn the screw in or out is the bike dies. Dos this mean i need to go up in my jet size. Or do i need to follow a different procedure for multi carbs.

 

[Thevmaxrider]

Don't forget to sync the carbs, or you will be chasing your tail!

+1!!!!!!! Also, as your bike may have enough mileage, you should look at checking your valve clearances some time soon. If you have valves out of spec all the tuning in world is for naught. Carb synch and proper valve shimming are needed to get the best tune on the bike. After that is gets easier, until the Mod Monkey gets ahold of you!!!!!

 

[VMax-Mike]

As i posted i tryed the scew adjustment and no change before engine dies, I turn it in and the bike runs the same until i get to the point of stalling the motor and it dies. at this point screws are just about seated. im thinking i need to go up a size on one of the jets or maybe both. But i dont want to rejet unless i have to. carbs are set up vary good and engine only has 9000 miles on it valve soung real good and bike ran perfect before i drill exhaust. In fact now that the vboost comes on at idle and rpms are at 1000rpms the bike runs perfect. I just think somthings wrong because i have no change when i turn the idle air screws.

 

[Thevmaxrider]

Drilling the exhaust will make the bike run rich. The way you have to think of this is that you have allowed the outlet of the engine to flow better. This increases the amount of exhaust gas that escapes the combustion chamber. The intake side has a limited intake size (limited by the airbox inlet and carb throat diameter) so you will have a greater intake velocity and will have a lower intake pressure. Your fuel system operates at a higher pressure than the intake pressure (atmospheric in the bowls through the vent tubes) so when the intake pressure drops it in effect pulls the fuel into the carb throat. The pressure differential partially dictates how much is drawn in. By lowering the intake pressure you increase the differential and more fuel is drawn into the carb throat. Thus the bike goes rich.

This is why jet kits such as Sean's need you to put in larger main jets when installed on the bike as they raise the intake "pressure", and allow the engine to take in more air, thus applying the same princples as above you will have less fuel flow into the carb throat. Putting in a larger main jet allows more fuel to flow and corrects the situation.

Remember, if you change the flow at either end of the engine you will have to check your jetting.

 

[VMax-Mike]

I dont agree but maybe some else can step up and change my mind. I was always tought more exhaust flow will make the engine lean. thats why we put bigger valves longer duration cams better flowing air filters and better flowing exhaust. so we can add more fuel to the mix and the engine can discard the bigger event happening in the cylinder due to more fuel. Your anser is well spoke but i dont agree.

 

[one2dmax]

If you increase the ability to pull air in then you can start talking about leaning it out. By just adding a better flowing exhaust you are able to make the engine a better vacuum. So, now it's pulling harder on the carbs which means it pulls in more fuel. But, the same amount of air.

Numerous dyno's don't lie. Go ahead and do some dyno testing for yourself if you don't believe what they are telling you.

 

[Rusty McNeil]

As i posted i tryed the scew adjustment and no change before engine dies, I turn it in and the bike runs the same until i get to the point of stalling the motor and it dies. at this point screws are just about seated. im thinking i need to go up a size on one of the jets or maybe both. But i dont want to rejet unless i have to. carbs are set up vary good and engine only has 9000 miles on it valve soung real good and bike ran perfect before i drill exhaust. In fact now that the vboost comes on at idle and rpms are at 1000rpms the bike runs perfect. I just think somthings wrong because i have no change when i turn the idle air screws.

Am I hearing that you have the Vboost open at idle?

If that is the case, you will definitely have to raise the idle to about where you said, nothing wrong with that. Plus that lumpy idle sounds awesome

Also, if you have the vboost open at idle then any adjustments to the carbs a/f screws or synch adjustments are going to be mostly meaningless, you need to close the vboost so that one carb feeds one cylinder while adjusting this stuff.