2 into 1 intake discussion

[WINDYCITYJOHN400]

Windycityjohn where are you ?

 

 

Just waiting for the haters to chime in..

 

Ok...I'm going to give you my take on this....I'm 40 and I've got LOTS of time on 2 into 1's

 

As I've said before, I don't like the Trinity design. (It puts the carb too close to the reeds and the intake charge has to make a very hard turn coming out of the carb and hits the reeds at a hard angle as well)

The GRAYDON design is the way to go. (They don't make them any more, but you can find them)

The great debate is always based on info from the bad Trinity design.

A 35PWK can properly feed a pretty big motor with a 2 into 1. Your jet size goes up due to the high air flow. On a bike with twin 35's your jetting might be 142-148 mains...with the single 35 on a Graydon you would be running a 178. Everyone who says that you loose top end is speaking under the impression that your somehow not getting enough air into the motor due to having one carb. This is rumor and false. Those same guys tell you to run twin 28's or maybe 33's! How would you flow more air into the cylinder if the carb was smaller? Any one ever ask the question..."How the Hell do you feed a Honda ESR380 with just one carb?" The YZ390 had one carb. And while I'm on a roll....so did the freekin' LT-500!!! That's like saying your banshee can be 250cc's per cylinder. So lets stop bashing the thought that it can't be done.The concept is to understand that each cylinder is only drawing an intake charge 1/2 the time. The whole point of a boost bottle or crossover/transfer tube is to keep that other carbs flow from completely dying while it's waiting for it's own piston to ask for more fuel. You will find that the motor just jumps out of the "mid rpm" type adjustments faster than it would with twin carbs. This is because the carb is very quickly at a high airflow rate. I've said before....We all understand the notion that a NASCAR motor on a super speedway needs to be wide open throttle to make top power. (why is it so hard to get guys to picture that a V-8 motor can run well with one carb...a 2-cylinder 2-stroke = @ the same flow as a 4-cylinder 4-stroke)

You get that crisp low end power with the 2 into 1 due to the strong intake suction when you crack the throttle. That doesn't stop there. It pulls hard all the time because you have 2 cylinders making the carb flow constantly. This makes them easy to tune once you get in the ballpark. You never flood a cylinder because of a float issue in one carb but not the other. Your jetting changes are CAKE because you can twist the carb on it's side and get at the jets very easily. Even pilot jet changes are a walk in the park! One spring = less throttle effort.

 

As we speak I'm running a 36PWK on my wife's 370cc D+M built (Doug's dune port) Long Rod motor with the new cool head. I'm running the FMF fatty gold's with the Turbine core silencers to make it more controlable for my wife. (If I put some SB CPI's on it she'd be flippin' over backwards in no time even though the bikes got a +6 arm.) The carb has 178 mains and a 42 pilot. (I'm still working on finding the best needle for this combo)

How strong is this motor breathing thru a 2 into 1?....I'm running 12 paddle haulers with a 75" rollout and a +6 arm! I'd feel fine recommending running a GRAYDON 2 into 1 on everything up to at least a 392 cub.If someone can convince you that your loosing 3-5HP on the top end....explain that you spend ALOT more time running just shy of those peak HP rpm's and that in the lower RPM ranges you motor pulls stronger overall.

 

If you don't agree with my take on the topic....that's just fine.

I'll be at SilverLake on the 11-12-13th and if you are willing to point yourself out....I'll begin teaching CV theory in person.

Hope that was the input you were waiting for.

[WINDYCITYJOHN400]

P.S.....The brand new twin Mikuni 28's that were on this motor are sitting on the floor in my garage and they are "FOR SALE" complete with throttle cables and intakes. So If you don't by my opinion...than at least buy my carbs.

[Wallynut]

I've been running the trinity 2-1 for over 4 years using a 33pwk. I can't comment on Graydons since I've never used them, I can understand the theory on the longer in-take track tho. I ride on Wisconsin atv trails which are usually sandy and sometimes twisty. There are no sand dunes that can compare to out west. I can't remember what the jetting is since I don't normally have to adjust it much except for the air screw or for more then 20degree temp change in fall, for 70 to 90+ degreee days, I don't change my jetting. I like the single carb setup for the riding I do because of the control I have in slower trail sections, I do not have to feather the clutch, my clutchs last a long time. Now some will cry about using a 33pwk, but for my riding it works. Better air flow thru carb at anything below half throttle openings. To really help that out, I fab'd my own vane at the carb intake to concentrate airflow at the smaller throttle openings, it's soldered in and has no effect at wide open thottle. The 33pwk may not be the best choice when compared to dual 28's or larger, but drag racing or wide open runs are a very small part of my riding. I can still blow away modded 400's or stock 450's. If I had areas where I could run wide open or drag race more, I'd go back to a dual carb set-up. I have never regretted going this route, my last banshee was set up for drag racing and it didn't work for the riding opportunities we have.

[PhilMoore]

I have a Graydon 2 into 1 carb manifold, aluminum airbox and K&N filter. I can't remember the size of the carb that came with it.

 

It works awesome, and I would not go back to two carbs, unless I was a serious drag racer/tuner.

 

The sole reason I got this kit, is I hated messing with jetting (summer/winter and altitude changes for dune trips) on the stock carbs, and I figured if I am replacing them I may as well go with one carb to make it as simple as possible.

 

I am more than happy with my Graydon setup and would not go back to two carbs.

[SLORYDER]

i wonder if your carbs aren't synced properly if that is a cause of the crank going out of true..?

[mikechief]

i wonder if your carbs aren't synced properly if that is a cause of the crank going out of true..?

 

 

Smokin sum crack today slo ?

[SLORYDER]

Smokin sum crack today slo ?

 

Naw, just spent 3 hrs out in the hot sun with a pair of dark coveralls on. Feels like my brain is on simmer lol

 

It just seemed like maybe having one cylinder putting more stress on one side of the crank than the other constantly could lead to something going out of wack eventually..?

[WINDYCITYJOHN400]

i wonder if your carbs aren't synced properly if that is a cause of the crank going out of true..?

 

 

No the cranks go out of true because your motor fires the right cyinder first.

Right-Left-Right-Left....if you could make it alternate every other time you start it...Left-Right-Left-Right then Right-Left-Right-Left...it would even out the stress....you try working on that one for a while. Maybe swap your wires every time you start it.

[SLORYDER]

No the cranks go out of true because your motor fires the right cyinder first.

Right-Left-Right-Left....if you could make it alternate every other time you start it...Left-Right-Left-Right then Right-Left-Right-Left...it would even out the stress....you try working on that one for a while. Maybe swap your wires every time you start it.

So if one side was constantly under more stress you don't think that would accelerate the problem?

Edited June 5, 2010 by SLORYDER

[WINDYCITYJOHN400]

In theory...one could argue that it might. But I've got one piston that's a 65.5 and ones a 65.75 I don't think a weld is going to let loose because of that. Un-welded stock cranks come out of true just because you start making more power overall than they can handle without a good weld.

 

Besides, you had a nice 2 into 1 post going. Why we talking about cranks?

 

Hey Sloryder, what kind of motor and riding are you asking about 2 into 1's for? Looking to make a change, or are you building something new?

[AKheathen]

cranks separate from flex but either major imballance, force, or worn bearing tolerances. i doubt anyone is running a perfect even topend, anyway, and cranks would e flying apart left and right, since proaly more than 90% are unsynced.

[Larry's Shee]

No the cranks go out of true because your motor fires the right cyinder first.

Right-Left-Right-Left....if you could make it alternate every other time you start it...Left-Right-Left-Right then Right-Left-Right-Left...it would even out the stress....you try working on that one for a while. Maybe swap your wires every time you start it.

Are you on Chcago Crack? Changing plug wires wouldn't change which cyl fires first. Unless you had real weak cyl you only have 50% chance that it would start on same cyl next time started.

[firebanshee]

What's to talk about, Putting a single carb set up on something that came from the factory with dual carbs would be like putting a 2 barrel carb on an engine that came from the factory with dual 4s or a six pack.

[WINDYCITYJOHN400]

Are you on Chcago Crack? Changing plug wires wouldn't change which cyl fires first. Unless you had real weak cyl you only have 50% chance that it would start on same cyl next time started.

 

 

 

UUUMMMMMM This was said in sarcasm. It was a joking response....that's what the smilies are telling you.

[WINDYCITYJOHN400]

What's to talk about, Putting a single carb set up on something that came from the factory with dual carbs would be like putting a 2 barrel carb on an engine that came from the factory with dual 4s or a six pack.

 

When's the last time you saw a 6-pack in action on the strip? Most high HP drag cars are running a single dominator carb with a low rise manifold on a V-8.

This topic is about the motors running a 2 into 1. I own a 472 Cheetah and I wouldn't run a 2 into 1 on that motor. But for a 392 or smaller the GRAYDON is a strong option that doesn't loose HP like you think it does. Read the entire post. I own one and it's a runner. I removed the twin 28's that were on it. Do you think I did that to loose HP? It's easy to bash stuff that you don't agree with. This post is asking how to make it work. Your signature tells me that you motor and your fuel are well beyond providing a helpfull input here. Plenty of people have posted saying that they have run them for years and like them. If you think they are throwing away power....fine. You just feel safe knowing you'll be out front with your twin 39's on alky.