2 into 1 Intake crossover

[hoffman900]

Cross overs are a band-aid for what ails a inefficient runner design of unequal lengths that transmit poor fuel distribution amongst the cylinders

There might be something to a crossover (balance) tube on a diaphragm type carburetor. They still appear on fabricated manifolds for SU type carburetors on LBCs. Some racers block them off for a small gain on the flow bench and win races, but others also win with them open, or slightly restricted (not completely blocked off).

I wouldn't be surprised if a lot of street bikes ran better with a 2-1 intake than a 2-2. Figuring out the cfm demands of the engine is a good start for figuring out carburetor size.

 

[TwoManyXS1Bs]

Ok, bearcat, you're gonna shoot me for this...

Find a good/used 2 into 1 exhaust, mount it, lean-out the left carb, chug over to the smog station, get okey-dokey, chug home, put back to normal.

 

[Jack]

There might be something to a crossover (balance) tube on a diaphragm type carburetor. They still appear on fabricated manifolds for SU type carburetors on LBCs. Some racers block them off for a small gain on the flow bench and win races, but others also win with them open, or slightly restricted (not completely blocked off).

I wouldn't be surprised if a lot of street bikes ran better with a 2-1 intake than a 2-2. Figuring out the cfm demands of the engine is a good start for figuring out carburetor size.

There was a reason why Triumph dropped the 2 into 1 manifold set up decades ago for the shear fact that 2 carbs will move greater amounts of air without impeding velocity like a single oversized carb does and if you're seeking performance or throttle control, you ditch the CV's in the trash in favor of a carb that inhibits less air drag ,can't think of any race where a XR750,XS750 or a Triumph 750 crossed the finish line with mounted CV's

 

[hoffman900]

There was a reason why Triumph dropped the 2 into 1 manifold set up decades ago for the shear fact that 2 carbs will move greater amounts of air without impeding velocity like a single oversized carb does and if you're seeking performance or throttle control, you ditch the CV's in the trash in favor of a carb that inhibits less air drag ,can't think of any race where a XR750,XS750 or a Triumph 750 crossed the finish line with mounted CV's

If rules require them. That's the case with the cars with SUs in vintage and SCCA racing.

 

[itrguy]

Heres mine

 

[bearcat]

Sweet bike and I'm diggin your style and the front drum. Here how it pans out. I have a significant improvement. Is is perfect? I'm thing better than a bandage, but I don't have the diagnostic equipment to check it. The fist picture is my plugs before the crossover and the flow diverter-vane were installed. The plugs in the second picture ran significantly cleaner after the modification. I think the crossover would be an improvement on any 2 in 1 providing the compression is close? Can't tell you it will work in every situation, but it's quite obvious, my bike is running better and idling way better. I'd like to pull the diverter, but not before l take it to a shop and have it pre-tested for emissions. I never tried running it with just the diverter, wish I would have. Thanks to those who encouraged and my buddy "Reno" for suggesting the crossover. Nothing ventured nothing gained?

 

[TwoManyXS1Bs]

Very significant improvement, congrats...

 

[gggGary]

This gets the E for effort award for sure!

 

[bearcat]

Thanks Gary "Old guy, NO expert." I like that. It was an old timer that steered me this way. The old timers are a invaluable resource, all you need to do is ask

 

[Jack]

Thanks Gary "Old guy, NO expert." I like that. It was an old timer that steered me this way. The old timers are a invaluable resource, all you need to do is ask

You've done nothing but band-aidded that carp of a 2 into 1 manifold,your fouled plug is the key telling you this,you have a fuel distribution problem,mostly caused by the turbulence at the runner divider,you want a rolled over not sharp edge where the two runners meet ,isn't dosen't take a rocket scientist to figure it out by looking at your manifold,drawing air from the opposing filter isn't the method to corect an overly rich cylinder and this comes from old timer who's been turning wrenches for some forty plus years. When you build something half ass,you'll get half ass results

 

[gggGary]

Look at the rest of the bike, he's not after horsepower, he just needs to pass emissions and hopefully even out the distribution so it runs decent. If what he did works for how he rides; more power to him.

Take a look at any old straight six car motor if you want to see a rough intake. A connection to the exhaust manifold to keep the puddled gas boiled off was normal practice.

That 40mm lectron looks huge!

Hey he has a front brake, puts him miles ahead (or behind) the no front brakes guys.

 

[bearcat]

And then there's always that old guy that insults you, by calling your work, "half ass" that you'll never look to for advice. My hats off to you "Jack" in all my times reading these posts, I've never seen one criticize another's work like that. You get the "Jack Ass" award. Thanks for nothing

 

[bearcat]

Gary, wanted to address the carb. I totally went by Lectron's advice. I bought it directly from them set up for my displacement. Again like several aspects of my bike, tried to be a little different. Comes with some curves

 

[TwoManyXS1Bs]

What is the emissions station looking for anyway, CO, HC, NOx, money?

Let us know if you passed...

 

[Jack]

And then there's always that old guy that insults you, by calling your work, "half ass" that you'll never look to for advice. My hats off to you "Jack" in all my times reading these posts, I've never seen one criticize another's work like that. You get the "Jack Ass" award. Thanks for nothing

If you can take being criticized for your poor workmanship then you shouldn't of posted that abortion of an intake. I take pride in my workmanship as I can only imagine what would happen if I sent out half ass ported intakes and then recommend to the customer to install a balance cross over to counter balance the fuel mixture atomization to prevent plug fouling. So Yeah, I take pride being an Critique " Jack Ass" and You still get the "Half Ass Workmanship Award" You simply didn't take the time to educate yourself
on how to fabricate a functional intake manifold that wouldn't of given the problems you the encountered.

 

[hoffman900]

Jack,

You could point to a lot of bikes and cars and say the same thing. IMO, for the bobber, rat rod crowd - it's part of the aesthetic. The guy isn't in business to make money, it's just a dude having some fun and trying to get pass emissions. He didn't come here asking, "how can I make more hp with this intake", it was "how do I pass emissions?". Relax. I'm sure someone like Darin Morgan or Curtis Boggs could look at your cylinder heads and find stuff wrong or not optimized, but I'm sure they wouldn't be an ass about it.

Cheers,
Bob

 

[Jack]

Look at the rest of the bike, he's not after horsepower, he just needs to pass emissions and hopefully even out the distribution so it runs decent. If what he did works for how he rides; more power to him.

Take a look at any old straight six car motor if you want to see a rough intake. A connection to the exhaust manifold to keep the puddled gas boiled off was normal practice.

That 40mm lectron looks huge!

Hey he has a front brake, puts him miles ahead (or behind) the no front brakes guys.

I use to race"Slant Sixes" and Chrysler nailed the 4 barrel manifold limiting the use of fuel damns for proper fuel distribution to certain cylinders.

 

[Jack]

Jack,

You could point to a lot of bikes and cars and say the same thing. IMO, for the bobber, rat rod crowd - it's part of the aesthetic. The guy isn't in business to make money, it's just a dude having some fun and trying to get pass emissions. He didn't come here asking, "how can I make more hp with this intake", it was "how do I pass emissions?". Relax. I'm sure someone like Darin Morgan or Curtis Boggs could look at your cylinder heads and find stuff wrong or not optimized, but I'm sure they wouldn't be an ass about it.

Cheers,
Bob

It would be difficult for Curtis or Darwin to find faults with my porting technics since my ports are completely reconstructed to a certain engine combination in limiting flow at certain lifts while biasing it at higher lifts and having it taper off of which I researched this information from speed talk and from close connections who've been porting heads for decades.

And I have yet to mention anything about making more HP.

And yes I can be out spoken at times but I will not apologize,for this is who I am.

 

[tonyc]

You would do well to heed Jack's advice.

 

[bearcat]

Don't want his advice and never needed that advice. Anyone on this forum could figure out going back to 2 carbs would work. So there's not terribly insightful or innovative there. Can't even understand his rambling like, " looking at your manifold, drawing air from the opposing filter" ??? Didn't understand much about the intake at 1st and know just a little more now. Just wanted to see if i could fix what I had. My first build and it's not for racing, just for fun. I thought about scrapping it many times, been encouraged by to many people not to give up on it. I will run 1 carb, may or may not be the same intake, we'll see? I'll call it my "Jacked Up 2 Into 1 Intake", in his honor.