A
Anonymous
Guest
Jack- that is really inspiring.
Mikunis are mounted on X-flow
- Thread starter MustangSix
- Start date
Those are great carbs. I was running a stock Keihn on my Harley with a Thunderslide kit. Holy cow! It was so responsive and fierce. That, with a K&N filter resulted in 65hp and 73t on the dyno afterward. I can't remember what it was prior to the install, but the increase was significant as anyone I was racing can testify. Later with CraneCam ignition on board, I never felt compeled to mess with the head, valves or cam.
The carb was sturdy, dependable and flawless in it's actions. I think you will enjoy the monster you've created. Nice move.
The carb was sturdy, dependable and flawless in it's actions. I think you will enjoy the monster you've created. Nice move.
A
Anonymous
Guest
Hey Jack,
You know that you will just have to put velocity stacks on that thing.
The look alone would make a ZO6 faint!
John
You know that you will just have to put velocity stacks on that thing.
The look alone would make a ZO6 faint!
John
John, The thing that would make this really smooth would be to have you help me cast some stubs from alloy to replace these fabricated tubing bits! 
I've go three ideas on how to finish off the carbs.
First, I have just enough room to enclose them under the hood and run a remote air filter to them leaving the bonnet smooth.
Or, I could fabricate an aluminum airbox that will fit against the bonnet. The bonnet will have a cutout with a mesh screen for air intake and no filter. Since I run only on pavement and Florida is not dusty, that is actually a feasible idea.
The third idea would be to add six K&N filters like these and have them stick out the side of the bonnet. The cost is kind of high, though.
I've go three ideas on how to finish off the carbs.
First, I have just enough room to enclose them under the hood and run a remote air filter to them leaving the bonnet smooth.
Or, I could fabricate an aluminum airbox that will fit against the bonnet. The bonnet will have a cutout with a mesh screen for air intake and no filter. Since I run only on pavement and Florida is not dusty, that is actually a feasible idea.
The third idea would be to add six K&N filters like these and have them stick out the side of the bonnet. The cost is kind of high, though.
A
Anonymous
Guest
I'd go with option number 3 
....Sometimes ya just have to spend the money.... 
Later,
Doug
....Sometimes ya just have to spend the money.... Later,
Doug
Option 3 is $22 each! $132 plus shipping! That would make the air filters worth more than the rest of the induction system! Maybe if I can find a cheaper version.....
You just have to let those carbs be seen :!: Isn't a hood optional 
:
Those would look so good driving up and down the beach in daytona.
Jim
: Those would look so good driving up and down the beach in daytona.
Jim
No beach! I can just picture all this nice, shiny aluminum after a day of salt water spashing all over it! 
i used to ride my shadow up and down the beach. both before and after i used a lot of wd-40 on it. never had any problems with corrosion at all.
Besides the beach is very wide, you are farther away from the water than you think. the sand is so dry in a lot of places you can even ride a bycycle there.
Now I did know a guy who used to put his sail boat in the ocean in daytona by backing his CJ-5 and boat trailer in the water. That jeep defined the word RUST. everything but the seat, tires and winshield rusted.
Jim
Besides the beach is very wide, you are farther away from the water than you think. the sand is so dry in a lot of places you can even ride a bycycle there.
Now I did know a guy who used to put his sail boat in the ocean in daytona by backing his CJ-5 and boat trailer in the water. That jeep defined the word RUST. everything but the seat, tires and winshield rusted.
Jim
A
Anonymous
Guest
JMHO, but
1. MUST have a filter
2. individual filters too $$$, not well shaped as entries
3. best: flared stacks with 270 degree roll-over at lip, ending inside air box with 3" OD duct leading to remote filter. Must have still air on all sides including above and behind stacks for max air flow.
A brave person might try to do the math for a Helmholtz resonator for shape here, but I think the volume has to be pretty big...
1. MUST have a filter
2. individual filters too $$$, not well shaped as entries
3. best: flared stacks with 270 degree roll-over at lip, ending inside air box with 3" OD duct leading to remote filter. Must have still air on all sides including above and behind stacks for max air flow.
A brave person might try to do the math for a Helmholtz resonator for shape here, but I think the volume has to be pretty big...
A
Anonymous
Guest
Jack! Nice work - boy that X-flow sure simplifies what I had in mind for a log head...!
Some experience for ya:
1. The piston in these carbs rises as the velocity in the throat increases. The rate-of-rise is controlled by the size of the orifice that is routed to the top of the piston - it's pulled up by the suction across the venturi. The rate-of-rise controls 2 things: it stops the leanness associated with too-fast throttle openings and it allows the venturi properties to be consistent from the beginning-to-end of the long intake 'pulse'. This allows the jetting to act reasonably when you make changes, so it all makes sense better than with the slide-type carbs.
2. One of the little holes you see in the filter end of the carb is there to vent the fuel bowl so that the vacuum in the Needle Jet can lift the fuel. The other one is the Emulsifier Orifice that adds turbulence to the fuel in the mixing tube(s). Both must be kept VERY clean or troubles will result. Adding and air horn of 1"-2" length in front of this end increases flow by up to 15%.
3. The Needle Jet is the 'hole' where the Jet Needle of the slide fits. The taper of the Jet Needle is often adjustabel for position: it can be raised (richer) or lowered (leaner) via a series of grooves in the top of the Needle where it drops into the slide. This is your Midrange Adjustment.
4. The rest is pretty intuitive: the Idle Jet and it's associated Air Screw controls the mix from 0 RPM to about 1200 RPM, so it will have a large effect on low speed in these I6 engines. Above 1200 RPM, the Needle Jet begins to do it's part. In the range of 1200-5000 RPM, this is the dominant mix control, with the Idle circuit losing any authority above 1800 RPM. So, these 2 circuits blend a little and cover each other's errors together. The Main Jet size directly controls the mix from 4000 RPM up, but obviously, since it is the FUEL HOLE size, it has some effect on the Jet Needle and Needle Jet action: generally, raising the Main Jet by, say 10% size, richens the high end 10% while richening the 1800 RPM range by just 1%.
Since the I6 probably won't journey into the 6000+ range much, you will be playing mostly with the Idle circuit and the position (or size) of the Needle-Jet/Jet-Needle pair. And, the Needle-Jet/Jet-Needle ARE a pair: they must be changed together.
If you get stuck or need some hints, drop me a PM and we can get into more detail. I've worked with these gems since 1970....
Some experience for ya:
1. The piston in these carbs rises as the velocity in the throat increases. The rate-of-rise is controlled by the size of the orifice that is routed to the top of the piston - it's pulled up by the suction across the venturi. The rate-of-rise controls 2 things: it stops the leanness associated with too-fast throttle openings and it allows the venturi properties to be consistent from the beginning-to-end of the long intake 'pulse'. This allows the jetting to act reasonably when you make changes, so it all makes sense better than with the slide-type carbs.
2. One of the little holes you see in the filter end of the carb is there to vent the fuel bowl so that the vacuum in the Needle Jet can lift the fuel. The other one is the Emulsifier Orifice that adds turbulence to the fuel in the mixing tube(s). Both must be kept VERY clean or troubles will result. Adding and air horn of 1"-2" length in front of this end increases flow by up to 15%.
3. The Needle Jet is the 'hole' where the Jet Needle of the slide fits. The taper of the Jet Needle is often adjustabel for position: it can be raised (richer) or lowered (leaner) via a series of grooves in the top of the Needle where it drops into the slide. This is your Midrange Adjustment.
4. The rest is pretty intuitive: the Idle Jet and it's associated Air Screw controls the mix from 0 RPM to about 1200 RPM, so it will have a large effect on low speed in these I6 engines. Above 1200 RPM, the Needle Jet begins to do it's part. In the range of 1200-5000 RPM, this is the dominant mix control, with the Idle circuit losing any authority above 1800 RPM. So, these 2 circuits blend a little and cover each other's errors together. The Main Jet size directly controls the mix from 4000 RPM up, but obviously, since it is the FUEL HOLE size, it has some effect on the Jet Needle and Needle Jet action: generally, raising the Main Jet by, say 10% size, richens the high end 10% while richening the 1800 RPM range by just 1%.
Since the I6 probably won't journey into the 6000+ range much, you will be playing mostly with the Idle circuit and the position (or size) of the Needle-Jet/Jet-Needle pair. And, the Needle-Jet/Jet-Needle ARE a pair: they must be changed together.
If you get stuck or need some hints, drop me a PM and we can get into more detail. I've worked with these gems since 1970....
Jack, just grab some plexi glass, heat form it to equal a 21 inch long by, say, 8 inch curve tapered back to the back of the hood. So everyone gets to see the mass of carbies!
The consider a plexiglass backing plate curved to fit the out side plexiglasson the hood. Add one large K&N pod filter at and end, and seal it with a couple of tin backing plates.
The correct procudure is to do Option 2. Torque improves a heap when the head loss is mounted farther away. All air flow in an engine is turbulent, but if you can make all steps to smoothen it out, it will help. Whatever you do, the whole universe must see you handy work!
I used to make motor control cabinates with a Hot Rodder at my cousins factory. Plexiglass is expensive, but easy to work if you have someone with the forming tools.
The consider a plexiglass backing plate curved to fit the out side plexiglasson the hood. Add one large K&N pod filter at and end, and seal it with a couple of tin backing plates.
The correct procudure is to do Option 2. Torque improves a heap when the head loss is mounted farther away. All air flow in an engine is turbulent, but if you can make all steps to smoothen it out, it will help. Whatever you do, the whole universe must see you handy work!
I used to make motor control cabinates with a Hot Rodder at my cousins factory. Plexiglass is expensive, but easy to work if you have someone with the forming tools.
A
Anonymous
Guest
Hey Jack,
The reason why you never got the triple SU intake is because the Exwife seud the crap out of me and won!
I had to sell all of my equipment.
But since I built all of the equipment in the first place, I'll be able to replace it. I've just been stuck at work everyday, and I do mean EVERYDAY! I only had Christmas day off. I'm at work now!
I will rebuild. There are just to many good engines out there that need a few simple parts that I can make.
Besides, I still want to go to SEMA one day, as a manufacturer/vendor.
It's not the first time I've been knocked down and it won't be the last. It's just a delay that I wasn't planning on.
John
The reason why you never got the triple SU intake is because the Exwife seud the crap out of me and won!
I had to sell all of my equipment.But since I built all of the equipment in the first place, I'll be able to replace it. I've just been stuck at work everyday, and I do mean EVERYDAY! I only had Christmas day off. I'm at work now!
I will rebuild. There are just to many good engines out there that need a few simple parts that I can make.
Besides, I still want to go to SEMA one day, as a manufacturer/vendor.
It's not the first time I've been knocked down and it won't be the last. It's just a delay that I wasn't planning on.
John
rickwrench
Famous Member
Jack,
For tuning those Mikunis, there are a few companies making stand alone data loggers for wide band O2 sensors out there. There is a write up about one from a company called "Innovate Engineering" in the Feb '04 (!?!?!) CarCraft. It's $350 bucks, but, you'd get a definite look at where the carbs may (or may not) need adjusting.
I, myself, am cheap, and would probably just get a bosch wide band sensor for 50-60 bucks, wire it for power, hook up a volt-meter, and translate the voltage readings on the fly (who needs data logging anyway?).
Rick(wrench)
For tuning those Mikunis, there are a few companies making stand alone data loggers for wide band O2 sensors out there. There is a write up about one from a company called "Innovate Engineering" in the Feb '04 (!?!?!) CarCraft. It's $350 bucks, but, you'd get a definite look at where the carbs may (or may not) need adjusting.
I, myself, am cheap, and would probably just get a bosch wide band sensor for 50-60 bucks, wire it for power, hook up a volt-meter, and translate the voltage readings on the fly (who needs data logging anyway?).
Rick(wrench)
A
Anonymous
Guest
Hey, Jack;
Just one other thing I thought about this afternoon: intake runner length and its effects. (This is just advice for tuning after you get it running.)
Yoshimura used to recommend twice the diameter of the carb throat as the minimum distance from the butterfly to the intake valve's seat. Anything less than that distance would cause 'flat spots' in erratic RPM ranges because the turbulence would never settle consistently between intake pulses. I can't tell how long your runners are, but just a hint in case you run into this...
Longer runners generate greater low-end torque (below 2500 RPM) because they allow compression of the moving air in the "tube length". These 'runners' are just the volume of the passage between the butterfly and the valve.
What RPM ranges are you anticipating running with this beauty?
Just one other thing I thought about this afternoon: intake runner length and its effects. (This is just advice for tuning after you get it running.)
Yoshimura used to recommend twice the diameter of the carb throat as the minimum distance from the butterfly to the intake valve's seat. Anything less than that distance would cause 'flat spots' in erratic RPM ranges because the turbulence would never settle consistently between intake pulses. I can't tell how long your runners are, but just a hint in case you run into this...
Longer runners generate greater low-end torque (below 2500 RPM) because they allow compression of the moving air in the "tube length". These 'runners' are just the volume of the passage between the butterfly and the valve.
What RPM ranges are you anticipating running with this beauty?
The runners are about 6" long from the flange and about 9" or 10" in total if you count the port length from the valve to the throttle blade. A lot longer than a typical motorcycle installation. The inside diameter is 1.5", but the ports taper down to slightly smaller than that as it approaches the valve, roughly 1.4".
I'm thinking of adding a 4" velocity stack to the end of the carb, increasing the effective length of the tract to about 13". That length is based on available space, not on any calculation.
I'm thinking of adding a 4" velocity stack to the end of the carb, increasing the effective length of the tract to about 13". That length is based on available space, not on any calculation.
A
Anonymous
Guest
IMHO this is the most effective method. It's important to note that:
1. some of the tuned length can be inside the box (reduces package size)
2. allows common remote entry or single big filter element (saves $$$)
3. the horn is capable of drawing air from all side, including BEHIND it, so that roll-over radius is needed (270 minimum). Far superior to having the stack end at in box floor as a radiused hole.
This box is too small for the stacks, though; there should be more room all around the stack radius. Distance from entry to box lid looks OK.
1. some of the tuned length can be inside the box (reduces package size)
2. allows common remote entry or single big filter element (saves $$$)
3. the horn is capable of drawing air from all side, including BEHIND it, so that roll-over radius is needed (270 minimum). Far superior to having the stack end at in box floor as a radiused hole.
This box is too small for the stacks, though; there should be more room all around the stack radius. Distance from entry to box lid looks OK.
Jack,
How about an airbox like this with a single big K&N mounted on the end, or remotely.
http://www.twminduction.com/airbox.htm
How about an airbox like this with a single big K&N mounted on the end, or remotely.
http://www.twminduction.com/airbox.htm
Ranchero63
Well-known member
Jack,
Where did you get those carbs? I need to get some VM's for my Triumph bobber. If you're paying $30 for 4 carbs, I should be able to get 2 for $15 right?
Where did you get those carbs? I need to get some VM's for my Triumph bobber. If you're paying $30 for 4 carbs, I should be able to get 2 for $15 right?
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