Twin dio possible?

[Carnie]

I don't know if it would be possible but I would have separate reeds and a custom intake that came together at a junction just before the carb.

[Bear45-70]

This running both cylinder coming to TDC at the same time is a torque builder and easier for the ignition but * on starting. A second pulse generator and make the crank throws 180 out will make a smoother running engine, easier starting and you can use one pipe if you wish.

[Majourlittle]

Alright, the idea of doing this would require the use of two engines. We will call the left cylinder motor "complete" and the right side "block"

The complete motor would be exactly that. A standard modified dio engine. The block would be a simmilar engine, but with the gearbox cut off so that it was an engine block, in the traditional sense of the word.

Basic idea would be to make a mating plate set that would be welded and reinforced on the mag sided of the complete engine and the variator side of the block engine. This would allow for the two engines to be bolted together so that the shafts lined up. This would allow for both cranks to be supported by two bearings each and would only serve as a way to access the crankshaft coupler.


Current plan would be to make an intake manifold that would attach one OKO carb to a y-tube that would feed both reid ports. Custom reid holders would have to be made.

Either make the tdc 180* from each other and attach a mag to each crankshaft, or put them 0* from each other and feed only mag. Currently, 180* seems more to my liking, but has its own set of problems. It would allow for a smaller carb selection vs running them 0*.


I am sure that there is quite a lot of logic missing in my initial assessment. I will investigate further in the next few days.

[Bear45-70]

Alright, the idea of doing this would require the use of two engines. We will call the left cylinder motor "complete" and the right side "block"

The complete motor would be exactly that. A standard modified dio engine. The block would be a simmilar engine, but with the gearbox cut off so that it was an engine block, in the traditional sense of the word.

Basic idea would be to make a mating plate set that would be welded and reinforced on the mag sided of the complete engine and the variator side of the block engine. This would allow for the two engines to be bolted together so that the shafts lined up. This would allow for both cranks to be supported by two bearings each and would only serve as a way to access the crankshaft coupler. Usually the center pieces are a new custom machining. I see no need to screw around with the outside of each engine half (the variator side and the flywheel side).


Current plan would be to make an intake manifold that would attach one OKO carb to a y-tube that would feed both reid ports. Custom reid holders would have to be made. Just use the lower part of a CT intake for each half. The individual intakes tubes need to be equal in length from the "Y".

Either make the tdc 180* from each other and attach a mag to each crankshaft, or put them 0* from each other and feed only mag. Currently, 180* seems more to my liking, but has its own set of problems. It would allow for a smaller carb selection vs running them 0*. Why not just add a second pulse generator and CDI box for the 180┬░ cylinder. You could use the original stator for both boxes.


I am sure that there is quite a lot of logic missing in my initial assessment. I will investigate further in the next few days.

[noiseguy]

Interesting. A few things:

I think running 180 phase on the pistons is something to avoid for a home build... it will just make things a lot simpler if they are in phase. 2 strokes aren't that lumpy, anyway, and there are many 4-stroke twins (old Triumphs) that ran in phase. 4 cylinder sport bikes are *just now* starting to run 90 degree phased cranks, b/c of the inherent complexity (it's superior in every other way.) I say this b/c 4-cylinder sport bikes are a $10K+ item... money's not the issue for them, and they've still been lazy about implementing it (GM V8 cranks have been made this way since the 50's).

I can't think of any twin 2-strokes that had a bottom-end feed carb as the scooter engine does. They always bolt to the back of the jug, with their own set of reeds. I'd never thought about the crankcase for a twin but I assume that these are sealed from each other... it would lower bottom end volume significantly to do it this way, and I can't imagine trying to get a non-sealed setup to work (the pressure waves would be all off.) All this means is that, in addition to the custom crank assembly (which is really the easy part) and the center crankcase (which is a bit harder, but doable with access to a CNC and some designing... ) you'll need to find a couple of jugs with intake ports, then block off the crankcase inlet with a plug. I think they are out there, or could be custom made from OEM design, but it's one more complication.

As far as the Y-duct with a single carb... I think it will be a lot easier to run down a throttle cable splitter and just run 2 carbs. If you look at the complexity and expense of doing it with one carb, I think the setup will be a lot more expensive and difficult than using 2 carbs. Single carb setups are meant for situations where you have low intake flow and want to keep the intake velocity high at low engine RPMs (think lots of low-end torque and low RPMs). The CM250 is a 4-stroke, and I suppose they want to keep low-end torque high b/c it's a beginners bike, and aren't concerned with high RPM performance... it's also cheaper for the OEM, and the CM250 is a cheap bike. For a 2-stroke I can't imagine a worse design compromise than trying to keep the thing running at idle and running well at WOT than a single-carb setup. Someone give me an example of a setup like this that's workable on a 2-stroke... would probably be on some sort of dirt bike.

... OK, I went and looked. RD350 engine. 180 crank, dual sealed crankcases. I still think in-phase is the way to go... it would reduce forces at the coupling, though I wonder if you wouldn't still need a set of inner bearings (see the RD350 crank.)

Also went looking for v-twin designs... b/c that would allow you to run same crank with v-shaped rod Example, though note that this is really 2 cranks linked together. Also note he has a common carb, and it doesn't appear to be working out for him:

http://www.youtube.com/watch?v=rY1PK8u28oE

[eliteguy50]

Some of the older 2t twin sleds ran single carbs. Then the sport sleds went twin and touring models kept the single carb a bit longer.

[swimmingfree]

i think 2 carbs are harder to tune two air screw to set and then the cable to set as well you may have one at wot and the other not ..just the smallest differences between the carbs will make a large deference if one motor is puting out 10 hp and the other is puting out 8 this wood not be good witch wood hold the hole thing back from top speed .. yes i do think the manifold wood be hard to build and the carb wood need to be at less a 30mm to feed the motors .. i feel better to have one carb holding you back then one side of this motor doing it .. it wood tack alot of skill to set the carbs and not as munch to set a carb..
swimmingfree

[Majourlittle]

Alright, the idea of doing this would require the use of two engines. We will call the left cylinder motor "complete" and the right side "block"

The complete motor would be exactly that. A standard modified dio engine. The block would be a simmilar engine, but with the gearbox cut off so that it was an engine block, in the traditional sense of the word.

Basic idea would be to make a mating plate set that would be welded and reinforced on the mag sided of the complete engine and the variator side of the block engine. This would allow for the two engines to be bolted together so that the shafts lined up. This would allow for both cranks to be supported by two bearings each and would only serve as a way to access the crankshaft coupler. Usually the center pieces are a new custom machining. I see no need to * around with the outside of each engine half (the variator side and the flywheel side). I would be attempting the machined halfs, but instead of making a whole new pieces set, I will canabalize the existing case-halves and build some attachment bracketry. It would be incredibly simmilar to the example in the OP's post but a mix of machined parts tig welded together.


Current plan would be to make an intake manifold that would attach one OKO carb to a y-tube that would feed both reid ports. Custom reid holders would have to be made. Just use the lower part of a CT intake for each half. The individual intakes tubes need to be equal in length from the "Y".I want to take the slant out of the ct intakes so that it would fit a little better between the cyls. I know that the slant is there for smoother flow into the chamber, but its my first idea run. I think that a twin carb setup will be used for simplicity sake.

I assume that tuning can be done on each individual cylinder by unplugging the coil and pulling the Spark plug. Tune each cyl seperatly and then it should be good in unison. ???

Either make the tdc 180* from each other and attach a mag to each crankshaft, or put them 0* from each other and feed only mag. Currently, 180* seems more to my liking, but has its own set of problems. It would allow for a smaller carb selection vs running them 0*. Why not just add a second pulse generator and CDI box for the 180┬░ cylinder. You could use the original stator for both boxes.I like this. Should be an easy splice.


I am sure that there is quite a lot of logic missing in my initial assessment. I will investigate further in the next few days.

[eliteguy50]

If you remove the spark plug, you need to oil the cylinder because it will be pulling in air instead of sucking in a premix charge.

[Bear45-70]

Alright, the idea of doing this would require the use of two engines. We will call the left cylinder motor "complete" and the right side "block"

The complete motor would be exactly that. A standard modified dio engine. The block would be a simmilar engine, but with the gearbox cut off so that it was an engine block, in the traditional sense of the word.

Basic idea would be to make a mating plate set that would be welded and reinforced on the mag sided of the complete engine and the variator side of the block engine. This would allow for the two engines to be bolted together so that the shafts lined up. This would allow for both cranks to be supported by two bearings each and would only serve as a way to access the crankshaft coupler. Usually the center pieces are a new custom machining. I see no need to * around with the outside of each engine half (the variator side and the flywheel side). I would be attempting the machined halfs, but instead of making a whole new pieces set, I will canabalize the existing case-halves and build some attachment bracketry. It would be incredibly simmilar to the example in the OP's post but a mix of machined parts tig welded together.


Current plan would be to make an intake manifold that would attach one OKO carb to a y-tube that would feed both reid ports. Custom reid holders would have to be made. Just use the lower part of a CT intake for each half. The individual intakes tubes need to be equal in length from the "Y".I want to take the slant out of the ct intakes so that it would fit a little better between the cyls. I know that the slant is there for smoother flow into the chamber, but its my first idea run. I think that a twin carb setup will be used for simplicity sake.

I assume that tuning can be done on each individual cylinder by unplugging the coil and pulling the Spark plug. Tune each cyl seperatly and then it should be good in unison. ??? The extreme angle on the carbs makes for * poor fuel control. If you do not run the second cylinder the tuning you do will be a waste of time. Both cylinders must be running or the air flow changes by half.

Either make the tdc 180* from each other and attach a mag to each crankshaft, or put them 0* from each other and feed only mag. Currently, 180* seems more to my liking, but has its own set of problems. It would allow for a smaller carb selection vs running them 0*. Why not just add a second pulse generator and CDI box for the 180┬░ cylinder. You could use the original stator for both boxes.I like this. Should be an easy splice.


I am sure that there is quite a lot of logic missing in my initial assessment. I will investigate further in the next few days.

[Majourlittle]

After typing it out, I realized that it was a stupid assumption.

I think that i will throw a few ideas around on paper and then come up with a mild prototype. Basically a set of stock engines to prove concept, then take it a little farther.

I think that a 180* phase is the way to go. Twin carbs and a single pipe will do. I also have a spare e frame that will serve as the mount for it all. Should be summer by the time i clear off my workbench to start up the grinder.

[eliteguy50]

After typing it out, I realized that it was a stupid assumption.

I think that i will throw a few ideas around on paper and then come up with a mild prototype. Basically a set of stock engines to prove concept, then take it a little farther.

I think that a 180* phase is the way to go. Twin carbs and a single pipe will do. I also have a spare e frame that will serve as the mount for it all. Should be summer by the time i clear off my workbench to start up the grinder.

Doing it with af05 blocks blocks would be a cheap test if you are only looking at a proof of concept. Screwing up af16's will be expensive.

[Majourlittle]

I do have two elite e engines! I also have a jacked af16 block. I think that this will be expensive anyway, but thats why its a hobby! I figure that if it works, i can take it a step further and make it into a 250cc.

Its all paper postulates though. More research to come.

[Carnie]

What's wrong with your mucked up af16?

[Red Eft Performance]

What are your plans for cooling?