Why single carb?

[skiri251]

It is very interesting to watch that single carb conversion thread progressing.

However I have a basic question.
Why is single carb better than multi-carbs?

Ease of maintenance, sure.
But more performance?

Back in 60's BSA had two models for the same engine (vertical twin, of course).
A65 Thunderbolt: single carb
A65 Lightning: twin carb
It is said that twin carb version is for sports riding with better top end.

Why did Honda choose to do multi-carbs on most (if not all) of the lineup?
It's not that they didn't have experience in single carb. They manufacture cars and I think some of them must have had single carb setup. In cars, it's the other way around, converting single carb setup to multi carbs for performance.

Single carb has advantages of easier maintenance and less cost (carbs) yet why didn't Honda do it in the first place?

 

[joedrum]

im not sure in the case of your bsa ..these were real carbs when you twist the throttle gas gose in ....cv carbs that came around later have huge lag time off the bat ... no racer would ever use them if they wanted the best ... cv carbs are over complicated to the same job poorer ..than a rider with smart throttle hand ...weber and oter carbs we are using here are much better carbs than these over done nightmares of bs tech ...if a guy had proper weber sized carbs that were made for a oldwing to begin with ...it would make the Honda cv carbs look like a joke ....so its rather easy to get simplicity and power over stock carbs with or at least the the same power ...and much better ridability

 

[slabghost]

I can't begin to explain thoughts moves or decisions made by the manufacturer. If contacted directly I doubt even they will provide a good response. As to why it's desirable for our oldwings I see it this way. 4 worn carbs are difficult to adjust for best performance and must be matched (synchronized) and they are prone to have issues from just about everything. Heat, humidity, fuel quality,and other things. The simplicity of knowing which carb is giving you issues is huge. If you have only one there's where you look. Vintage muscle cars had several carbs in some cases but the average owner would often choose a single large 4 barrel over the headaches of tuning several carbs and those had the advantage they shared a single intake manifold. One carb and manifold per cylinder on bikes will give the best performance when all is right. I'll not dispute that. But if we can get similar performance from one carb the simplicity is worth accepting the small loss of performance at certain points.

 

[ekvh]

The other plus that may come into play here is longer intake runner lengths increase bottom end torque which a lot of people would rather have than going up and down the gears. With the carb on top of the plenum, the length of force that the intake charge has is probably double the stock setup. There should be a delayed response early on since it has further to travel, but reports are to the contrary. Maybe the acc pump gets it there faster than the cv's can begin opening?? So far we only have butt dynos. Some people's butt dynos are more accurate than others.

 

[skiri251]

Ahhh worn carbs. That makes sense.
I guess you can replace four worn CV carbs with four brand-new latest flat slide ones like Mikuni TM but that it more costly than single carb so unless you are into racing or something it's not worth the effort.

Surely it was much easier for me to replace one worn Amal carb with one brand-new Keihin semi-flat slide carb on my BSA.

 

[skiri251]

ekvh » Thu Sep 26, 2013 10:26 am[/url]":2c042uj0]
The other plus that may come into play here is longer intake runner lengths increase bottom end torque which a lot of people would rather have than going up and down the gears. With the carb on top of the plenum, the length of force that the intake charge has is probably double the stock setup. There should be a delayed response early on since it has further to travel, but reports are to the contrary. Maybe the acc pump gets it there faster than the cv's can begin opening?? So far we only have butt dynos. Some people's butt dynos are more accurate than others.

Low end torque!
Yes I like that.
Initially I was kinda disappointed with lack of it on my Oldwing.
More torque and taller gearing and quiet crursing so that I can listen to the radio better.

I think I read somewhere that single carb BSA got a little more low end torque than twin carb version.

 

[Steve83]

skiri251 » Thu Sep 26, 2013 10:28 am[/url]":1ocrass8]
Surely it was much easier for me to replace one worn Amal carb with one brand-new Keihin semi-flat slide carb on my BSA.

Yes, it probably was. And don't call me Shirley. :hihihi:

 

[skiri251]

About the CV carbs:

Are they basically the same as SU carbs?
I thought SU was a high performance carb for vintage cars.

CV became ubiquitous in motorcycles in later years.
Does it have something to do with EPA? (supposedly perfect A/F ratio under any condition)

 

[dan filipi]

Wish I knew more about why CV carbs are better for performance.
I guess it has a lot to do with the charge being right there dumping straight in but I'll tell you I'm done with the stock rack after having run a single.
Even with my leaking runners and carb base gasket, idle is much quieter with NO primary chain noise! Very pleasantly surprised at that.

Acceleration at wide open throttle is at least close to the stock rack.
This weekend I'll know more.

Some would slam me saying I don't know what I'm doing or haven't adjusted or "set up" the stock rack completely. They can say whatever they want.
I have been on the GW forums over 7 years and reading many of the carb threads about what causes what problem.
At the meet last August, every 1100 there was spitting to some extent and I heard the same primary chain noise I have from at least 3 of them, especially when cold.
It's simply an imbalance in those stock carbs.
The best cause I've been able to narrow down that spitting to is vacuum leaks at the throttle shafts and/or worn/fatigued CV slider springs, I'm not certain. What I do know for certain is there is absolutely NO spit, cough, backfire, or pops out the exhaust running the single.
The C5 ignition helped but once I put the single on, all of that was gone.

I'm fine with a bit loss in power if that's the way it has to be to have my 1100 run like Honda intended it to. Smooth and quiet.

 

[ekvh]

Some would slam me saying I don't know what I'm doing or haven't adjusted or "set up" the stock rack completely. They can say whatever they want.

Nope, they're just slamming you because they're rude to begin with and didn't like the fact that you expected gentlemen's manners here. Nobody here is slamming you. If people don't like the fact that we are having fun trying different combinations, too bad.

 

[joedrum]

if a guy wants an oldwing to depend on ...no matter how they want to go ...you better play outside the box ...if you want truly dependable bike ...as good as the short block motor is ...that's my deal

 

[KYWinger]

Big, huge, expensive sigh here.......

Now, not only do I have to add 75-77 cams and a C5 ignition, I hafta go the single carb route....

:rant: YOU GUYS ARE KILLIN' ME!!!! :rant: Just kidding.............sort of............

Be well-

 

[westgl]

Well said everyone.

From my experience with Rev.#1 single carb conversion, on my GL1100

To me, it feels like, I have More power from Idle to Redline.

The added Torque is everywhere, and it is considerably more, this extra power can be felt and used.

I think, the multi carb. thing has a cool factor, the bigger is better, and Too much is never enough, scenario comes into play here.

I remember looking at the first Goldwing, and saying 4 carbs and 1000cc, I would love to ride that thing, but I was 13 years old at the time.

One carb, the right carb., setup/tuned properly for the engine size

Vs Multi carbs tuned properly.

If you over carb any engine it will not run properly, and will run poorer than a carb that is Sized & tuned right for the given engine.

I think the OEM four carb. rack has a certain amount of De-Tuning, built into it, the choked down carb., the CV and their slower ability to perform, that and that the butterflies are almost at the head, for a fast charge pull.

 

[skiri251]

KYWinger » Fri Sep 27, 2013 8:31 am[/url]":2xf8ehu8]
Big, huge, expensive sigh here.......

Now, not only do I have to add 75-77 cams and a C5 ignition, I hafta go the single carb route....

:rant: YOU GUYS ARE KILLIN' ME!!!! :rant: Just kidding.............sort of............

Be well-

Well, your oldwing looks gorgeous!
She doesn't look old enough for all these upgrades. :hihihi:

 

[skiri251]

westgl » Fri Sep 27, 2013 8:50 am[/url]":3c8wcoi0]
Well said everyone.

From my experience with Rev.#1 single carb conversion, on my GL1100

To me, it feels like, I have More power from Idle to Redline.

The added Torque is everywhere, and it is considerably more, this extra power can be felt and used.

I think, the multi carb. thing has a cool factor, the bigger is better, and Too much is never enough, scenario comes into play here.

I remember looking at the first Goldwing, and saying 4 carbs and 1000cc, I would love to ride that thing, but I was 13 years old at the time.

One carb, the right carb., setup/tuned properly for the engine size

Vs Multi carbs tuned properly.

If you over carb any engine it will not run properly, and will run poorer than a carb right that is Sized & tuned right for the given engine.

I think the OEM four carb. rack has a certain amount of De-Tuning, built into it, the choked down carb., the CV and their slower ability to perform, that and that the butterflies are almost at the head, for a fast charge pull.

More torque!
Hmmmm...
I must copy your single carb when all done then. :hihihi:

> I think, the multi carb. thing has a cool factor, the bigger is better, and Too much is never enough, scenario comes into play here.

Ahhh I remember Valkyrie TV ad:

"6 cylinders, 6 carbs" or something like that.

 

[KYWinger]

skiri251 » Fri Sep 27, 2013 7:54 am[/url]":3r6mepbr]
Well, your oldwing looks gorgeous! :hihihi:

Thanks skiri - 31 years of always being garaged pays off in the long run...

But seriously folks... compared to the cost of a new or almost new GL1800, I guess these three mods will come to less than $1000. That's better than shelling out $20K.

ESPECIALLY things that improve the bottom end (for us trailer towers).

 

[joedrum]

just take on one at a time ..... we are here to help ... your wing will be the envy of trailer pullers :builder: :mrgreen:

 

[ekvh]

One at a time??? That's no fun.

 

[joedrum]

your right eric like I ever done that ever ...not sheesh :hihihi:

 

[sledge]

I got a Single Carb Intake made about a year or two ago , and rebuilt a Carb to go on it too .... hope to put it on the Trike when it's finished . :music: