2 into one or not

[sleeper06]

I have an aggressive porting job,milled head,boss intake with stock carbs. Shee really moves well and screams now. would there be any advantage in putting a 2 into one with a 35mm carb on being that I have one in my hands right now. Do you think it will hurt upstairs compared to what Im running now.

[dajogejr]

I have an aggressive porting job,milled head,boss intake with stock carbs. Shee really moves well and screams now. would there be any advantage in putting a 2 into one with a 35mm carb on being that I have one in my hands right now. Do you think it will hurt upstairs compared to what Im running now.

 

 

Yes....how much top end you feel you can afford to sacrifice is up to you....

Will pickup bottom though.

 

However...it depends on how aggressive your porting is...it might like a dual carb setup better all around.

[Snopczynski]

I run one in the sand as well as 5 other guys I ride with. We even have a couple 4mill strokers with them. Seems to run really well, and no one yet has complained of a power loss.

[ironhead]

I run one in the sand as well as 5 other guys I ride with. We even have a couple 4mill strokers with them. Seems to run really well, and no one yet has complained of a power loss.

 

 

what size are the 4mill strokers running 35 or 38 ? im in the middle of building a 4mill and debating on witch to go with 35 or 38 . i already have the 2 in to 1 set up for a 33, but i dont think that will be enough with the port work from f.a.s.t.

[Banshee0028]

what size are the 4mill strokers running 35 or 38 ? im in the middle of building a 4mill and debating on witch to go with 35 or 38 . i already have the 2 in to 1 set up for a 33, but i dont think that will be enough with the port work from f.a.s.t.

Ironhead, I am in almost the exact same position as you, but I have a 35mm single carb. Trying to figure out if I should go 38 or not. What type of porting do you have? I have a woods port.

 

Sleeper: I love the single carb for my setup. Will most likely stick with it for a while...If you have an aggressive dune port, a 35 still may be ok, but it depends how much top end you are looking for....For my setup its probably not taking any top end away, at least not much if any.

[ironhead]

Ironhead, I am in almost the exact same position as you, but I have a 35mm single carb. Trying to figure out if I should go 38 or not. What type of porting do you have? I have a woods port.

 

my jugs are still at jeffs . i still need to talk with him alittle more before i decide what port to go with. i was leaning towrds a dune port but i still might ride some tight trails sometimes .how do u like your woods port ? are u running a 35 on a 4mil now ? if so how do u like it ?

 

sleeper06: didn't mean t hijack your thread sorry . i can tell u i love my 2in to 1 ,some people love them some people dont ,i realy could't notice that much loss at the top with mine ,if your looking for better low end ,easier jetting and better throtle response than go with it. If u alredy have one y not try it ?

Edited March 16, 2007 by ironhead

[dajogejr]

Here's really the bottom line. Do you want to play and dune or do you want to drag?

[Crazy05]

Here's really the bottom line. Do you want to play and dune or do you want to drag?

I take it you guys all have the triniy 2 to1. I have a homemade one and just got my bike ported. When I can I will be putting it on adyno then swapping to 2 carbs and dynoing again. Everyone says that 2 is much better than one. Unles you dont care if you lose hp for a more mild powerband. I expect that is exactly what I will find.

[Whitbread]

I have a stock bore and stroke banshee with a very aggressive drag port, milled head, boyesen reeds, and fmf fattys. I also made my own two into one intake from 1/4 plate and 1.5 X .065 wall square tubing, and kept the runners as short at possible (approx 1 1/8in middle). The first manifold i made had about 3 inch runners and it ran like crap; made another one with shorter runners and didn't change a single other thing and it was night and day difference. With a 34mm keihin pj and a dial a jet, its running better now than it ever did on the modified dual stock carbs. Way more low end and if anything it gained a smidgen of top end with worlds better throttle response all around. I'll never go back to duals, the easier jetting and lighter throttle pull would be worth it even if you did lose a hair of top. If you were only going to be doing drag racing i'm sure a single 42mm or 45mm would flow more than enough even on 400+cc motor. Cr500s and lt500r's run great on one carb and thats inhaling all 500cc's at once; even if you had a 500cc banshee, its only inhaling 250cc at a time.

[Crazy05]

I have a stock bore and stroke banshee with a very aggressive drag port, milled head, boyesen reeds, and fmf fattys. I also made my own two into one intake from 1/4 plate and 1.5 X .065 wall square tubing, and kept the runners as short at possible (approx 1 1/8in middle). The first manifold i made had about 3 inch runners and it ran like crap; made another one with shorter runners and didn't change a single other thing and it was night and day difference. With a 34mm keihin pj and a dial a jet, its running better now than it ever did on the modified dual stock carbs. Way more low end and if anything it gained a smidgen of top end with worlds better throttle response all around. I'll never go back to duals, the easier jetting and lighter throttle pull would be worth it even if you did lose a hair of top. If you were only going to be doing drag racing i'm sure a single 42mm or 45mm would flow more than enough even on 400+cc motor. Cr500s and lt500r's run great on one carb and thats inhaling all 500cc's at once; even if you had a 500cc banshee, its only inhaling 250cc at a time.

If only one of the cylinders is sucking at a time I would be inclined to agree. I also wonder if the runner length, even tho you shortened yours would slowdown the flow. I also cant help but wonder if the air have to make the 45 degree turn wouldnt cause some turbulance and uneven entry into the the reed cage. With one carb on a single intake and boot, it is a straight shot to the reeds. For duning and trailing its better. But all the fast guys say 2 carbs are better. Besides. Once you get it it dialed your hardly ever have to mess with it. Less of course you make a severe altitude change or the the weather drops a lot. And on Kiehins you dont have to remove the carb to change the mains. I have given this lots of thought cuz I too luv the simplicity of the single, but love the extra hp more.

[dajogejr]

I have a stock bore and stroke banshee with a very aggressive drag port, milled head, boyesen reeds, and fmf fattys. I also made my own two into one intake from 1/4 plate and 1.5 X .065 wall square tubing, and kept the runners as short at possible (approx 1 1/8in middle). The first manifold i made had about 3 inch runners and it ran like crap; made another one with shorter runners and didn't change a single other thing and it was night and day difference. With a 34mm keihin pj and a dial a jet, its running better now than it ever did on the modified dual stock carbs. Way more low end and if anything it gained a smidgen of top end with worlds better throttle response all around. I'll never go back to duals, the easier jetting and lighter throttle pull would be worth it even if you did lose a hair of top. If you were only going to be doing drag racing i'm sure a single 42mm or 45mm would flow more than enough even on 400+cc motor. Cr500s and lt500r's run great on one carb and thats inhaling all 500cc's at once; even if you had a 500cc banshee, its only inhaling 250cc at a time.

 

 

I'm quite sure one LARGE carb would be better than stockers, no doubt. But with a single carb setup on a drag port and FMF pipes, you're missing out on ponies for sure, and I'm sure you're aware of that.

I'm not trying to start a pissing match, but don't you think some drag or opened up pipes would suit that aggressive drag port better, like CPI, Shearers or the like??

 

I don't think, for DRAG purposes, a single large carb will compare to a set of 39s, etc. Small motor or big motor...

[Snopczynski]

okay, on all the 4 mills with stock type cylinders they run pwk 35's. The 4 mill cheetah bike has a 38mm lectron.

 

Another interesting fact that defies the laws of reasoning is: In 1993 I took 4th place in the modified 350 class at Sandfest. My bike I ran had stock carbs bored to 27mm, and a set of FMF Gold Series pipes. Ultimately I lost in the 3rd to last heat from a bad start and still almost caught the guy at the end of the track.

 

So, I think high hp and dyno numbers play a factor, but biggest thing that makes a bike fast and easy to ride is your setup, and making sure everything you run works well with your portwork and other engine mods.

 

If people say that this guys ort job works well with certain pipes or carbs then you need to stick to that schedule. You sorta need to pick some pipes and carbs that coincide with your portwork. Or tell the engine guy which pipes and carbs you want to run, then have him do the porting based on that.

[.]

I run a trail bike and did a lot of research on getting a 2 in 1. For the most part a 2 in 1 will not help you at all on the bottom end compared to a well tuned 2 carb setup. They have actually researched this quite a bit at LRD and used to have a big article about it on their website. For a trail setup, twin taperbored 28's to 30's are the best setup to run. (this is a trail setup though and not drag racing)

 

As far as a drag racing setup goes, with guys that are running 34's and higher, It would be hard to get a single carb to perform as efficiently as 2 carbs with that much flow going on. You'd have to have a huge carb in a small area as well, and it can be done, and probably if you sat there long enough with carbs, and tuning on a dyno, you could get them practically the same no matter what setup you're running, but as far as drag goes, the 2 carbs are going to be an easier setup all the way around as far as experience with tuning goes on here

[Whitbread]

I'm aware i'm missing out on some hp with the fmf's, but i do like the current powerband, its very strong but not peaky. The banshee still dyno'ed at 68 whp at lakes motorsports in michigan with the fmf's so i can't imagine i'm losing more than 5-8hp at the very top of the powerband. But doing mostly trail riding now, having a little more of a balanced band works very well for me. I'll eventually upgrade but building an 87 K10 with a twin turbo stroked small block and 8 inches of lift eats up alot of time and money. Unless someone has dyno results proving that a large single is better than duals, i agree that duals are better for a bike that is set up drag racing only. Thats where max performance at WOT is prime concern over anything else. Regarding runner lenghts, longer will normally give you more power but on a two stroke with reed valves, this doesnt really apply anymore. This is why you always see carbs as close to the reed cages as possible. Because when the reeds close, manifold vacuum is lost momentarily. The vacuum is what keeps the atomized fuel in suspension, and when the vacuum is lost, the atomized fuel will start to condense into droplets. And having long runners means more atomized fuel to start falling out of suspension. And engines like a fine atomization better than large droplets, the same reason a fuel injected motor will be more responsive and make more HP than a carb all else being identical. With the manifold that had long runners (3 inches), throttle response was incredibly slow and dull, even with proper jetting. By changing the manifold to a square tube with shorter runners about an inch long (instead of round tube to better match the reed cage ports) the throttle response and sharpness picked right back up. I contoured the inside so that there are no sharp turns or edges and its a smooth polished interior. Out of curiosity i put the modified stock size carbs back on to compare side to side. I could not tell any difference on the top end but the low and midrange was noticeably sharper and much more present with the single set up. I even had a friend time me from 2 points down my street with both set ups, I was actually running .21 seconds faster with the single over a 5 run of each average. I would highly suggest either trying it or riding someone else's to see how you like it, alot of people who knock it i doubt have tried it. I've never ridden taper bore carbs on the trail to compare it, i just know how it affected my bike with the stock size carbs. It may not make the most peak hp, but it makes the hp over a wider range. I agree with Snopczynski, more hp doesn't always mean faster, how easy it can be ridden is a bigger factor. Having 80 hp won't do you much good if you don't have it till 8000 rpms, that would be pain to ride anywhere but a drag race. The laws of reasoning arent being defied with you carb sizes Snopczynski. During the dyno testing to get the motor for my truck tuned, we found it liked a significantly smaller carb better even with twin turbos. We started off with a 750 cfm carb (say what a 35mm or 38mm would be on a banshee) and then tried a 570cfm (equivalent to a stock banshee carb), it made 18 more hp and 19 more ft/lbs of torque with the carb that all the hot rod guys said was too tiny. Anytime you can increase the air velocity through a carb venturi atomization gets better because the vacuum signal pulling on the main jet will be stronger; of course only to a point before you start to choke a motor. Sorry for the long post, jut trying to share some tech info i've learned from building and modifying engines and parts over the years and watching all of the dyno tests at work on what works and what doesn't.

[FIRST BANSHEE]

I have an aggressive porting job,milled head,boss intake with stock carbs. Shee really moves well and screams now. would there be any advantage in putting a 2 into one with a 35mm carb on being that I have one in my hands right now. Do you think it will hurt upstairs compared to what Im running now.

with what your running right now, you will see improvement bottom to top with the single 35. if you have way not try it.