Topic: Single Carb cb550 Video

[Bailgang]

Geez guys what's all the hubbub about? Somebody tries something different and everyone else takes turns bashing him? The single carb isn't for me either but I will give the guy credit for trying and I wouldn't necessarily call the guy lazy because it looks like it took some effort to build it. I see some possible issues as well but I'm not quick to assume either, other than a smoother idle I would highly doubt any performance gains in fact I imagine the builders intent was more for the "look" value than anything else. Yeah I think the 92 hp claim is absolute BS too.

If you want to see some crazy DIY carb setups then you should check out some Goldwing sites, going to a single carb setup is popular with GL owners mainly because rebuild kits can be pricey for them and or owners really are too lazy to figure out multicarb setups, some conversions are well done while others are just plain back yard engineering. The most amusing I've seen was where the owner made his own intake manifold using plastic PVC pipe. Nope that's not for me either, I instead spent the money to get the correct kits for the carbs on my GL1100.

[carnivorous chicken]

That's the configuration I alluded to in my post as functional -- a single carb in the middle of the cylinders. Compare the bends in that manifold to the one on that bike. Sharp, 90-degree bends? Small diameter pipe with no flare on the intake? I'm not going to belabor the point all day or argue with people -- some people like this, some don't, and I don't really care. It just doesn't look functional to me and, again, there is a reason why there aren't a lot of SOHC4 conversions to single carbs.

[Deltarider]

As far as I'm concerned, there's no debate whether that setup with one carb (probably ment as a joke*) will work well or even better than the original 4 carbs (it will not). I just question all this echoing of members here that #1 carbs must run awfully lean whereas no one so far can produce convincing proof. Then, when I present myself as a dumbhead that still doesn't get it, some even loose their temper. That tells ya, doesn't it? Don't get me wrong: I'm open for evidence based reasoning but not for stupid remarks from folks that can't distinguish the sound of a nice running engine from the not so nice sound of the exhaust.
* anyway that's how I see it.

[jonda500]

As far as I'm concerned, there's no debate if that setup with one carb (probably ment as a joke*) will work well or even better than the original 4 carbs (it will not). I just question all this echoing of members here that #1 carbs must run awfully lean whereas no one so far can produce convincing proof. Then when I present myself as a dumbhead that still doesn't get it, some even loose their temper. That tells ya, doesn't it? Make no mistake: I'm open for evidence based reasoning but not for stupid remarks from folks that can't distinguish the sound of a nice running engine from the not so nice sound of the exhaust.
* anyway that's how I see it.

+1!
I think it sounds great and I commend the creater for trying something different! I hope an air filter is added when it's ridden!
John

[BPellerine]

do a search for the build nelsinore ,the guy made a single carb setup for cb 750 that worked.bill

[Scott S]

 I think that 750 had dual carbs.

[Stev-o]

I think that 750 had dual carbs.

No Scott, it was a single Mikuni....


http://forums.sohc4.net/index.php?topic=116272.0

[Don R]

 Take a look at the 6 cylinder intake, the center runners are large, the next two get smaller and the two end ones are the smallest. This is an effort to equalize the flow. Math isn't my strong suit but assume 8,000 rpm, each cylinder needs air/fuel every other revolution that's 4,000 pulses per minute or 1,000 pulses per cylinder per minute. That's 16.6 pulses per second, There will be a steady pull but my guess is the closest cylinder will be the big dog. if the intake main tube stepped up in size toward the carb that could help some. Will it work? Yes. Will it win many races? Probably not.
 There are also reversion pulses going backwards when the cam is in overlap but that's another story.

[jonda500]

Still no-one seems able to expain it...
Not meaning to upset ppl, but where exactly is #1 getting the extra air from to make it run leaner than #4?

I have seen car manifolds with equal diameter but unequal length inlet tracts...
John

[Don R]

 Performance intake designers go to great lengths to make the runners the same for good performance. There's an entire industry devoted to it. Some engines are designed to a price point and corners are cut. They still run.

 On my big block, even with a high dollar intake I still have 4 different size jets on the 4 barrel carb to get the same fuel mix to all of the cylinders. Cylinders 5 and 7  are consecutive in the firing order of most V8's (18436572) and  are also on the same corner of the intake. Cylinder 7 is always leaner because 5 steals the flow before 7 can get it. To solve this we make a new cam to swap 4 and 7 in the firing order. When 5 and 7 aren't fighting for the fuel it makes more power and cylinder 7 has fewer problems due to running lean.

I can't explain the science any better but it's a proven fact.

 

[kghost]

Still no-one seems able to expain it...
Not meaning to upset ppl, but where exactly is #1 getting the extra air from to make it run leaner than #4?

I have seen car manifolds with equal diameter but unequal length inlet tracts...
John

How familiar are you with Fluid Mechanics (static or Dynamic)?

[Scott S]

I think that 750 had dual carbs.

No Scott, it was a single Mikuni....


http://forums.sohc4.net/index.php?topic=116272.0

 Ok, not the same bike I was thinking of.

[njclimber]

I bet it has nothing under load.

[Redline it]

That poor #1 cylinder, I'm guessing it doesn't get much fuel.

I'd have to consider one thing, how much less, the #1 is getting, but you could always implement a volume regulated stream by a little bit more of using the same length of tube. #4 would have a loop, that'd be bad ass, polished. Or use the 4 original old rebuilt, and calibrated carburetors that give you can of worms fuel delivery 24 7s. Or the 4 will work great one day and next they give you trouble. I have a little 400f I could spend a little time and make it show room condition, but I ride it instead. Mikuni 38mm fat jetted, would do the job just fine.