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Discussion Starter #1
I see that Harleys most often run a single carb and other than being Harleys, do ok.

So, why not a larger single carb intsead of two smaller ones on my 500T?
There's a cat selling a new Mikuni VM44 for $100 plus shipping on ebay and I can fabricate/weld fairly proficiently and have a decent pile of mandrel bent stainless that could be abused into a manifold.

What am I missing?
Seems like a much simpler way to go about it to me.
One carb = one set of jets to deal with, no syncing, one pod filter and would be unique.
 

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I think it has something to do with the 180 degree crank and impossibility of tuning. I'm pretty sure we discussed this a while back.
 

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Discussion Starter #3
I was under the impression that this was a 360* motor.....hmmm.
Why would it make a difference?
 

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Think throttle response.

A Harley is a fairly large displacement engine that operates over a relatively small rpm range.

Your Honda is not....
 

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I would be willing to bet that a single carb set-up would work fine on a street bike. Theoretically it should help most on bottom end and mid-range. Honda ran a single car on its twin cylinder CM185 and 200 for a couple of years. I say give it a try and let us know what happens. Worst case is that you spent some time on a project that didn't work, like none of us have ever done that before.

Ken
 

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Discussion Starter #7
I'm leaning toward it...the OEM carbs on this bike blow....and by blow I mean suck...and not in the nice, friendly "I'm glad you're home honey!" kinda way, but in the bad, oxidized, crusty, crumbly diaphragm kind of way.
 

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Heck do it...... HD's have the 305 415 thing happening so a even 180 degree crank wouldn't be much worse as far as unevenly reflected waves in the manifold

if it's a 360 crank...... single carb is ideal but I am reasonably sure some of the 180 degree cranked twins came with single carbs


as far as low rpm, throttle response and all that....... seen more than a few HD's that didn't mind wicking up and beyond 8,000 with a single carb

what is the redline on the 500T?
 

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i'm almost positive that the intake ports on 360 cylinders are also perpendicular, not splayed outward like a 350. perfect for trying to make a manifold.
 

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Discussion Starter #10
Hack: The redline currently is indicated at 8grand on this one, however after I finish the internal mods and exhaust it should be more than capable of upward of 9500-10k......s'not gonna be stock. I just sent a pair of cb450K4 (hotter from the start) cams to Delta for regrind in thier horsepower profile. Should have specs back when they return, but basically they're grinding the base circle down with a little work on the lobes. The final compression should be around 9.3-1 and I've started some port cleanup, mainly in the bowls and on the short side though I'm also going to work the valve guide protrusions a bit as well.
I'm contemplating doing some coating work on the engine as well. I added techline coatings to my autocross engine (220hp+ naturally aspirated 2liter Dodge).

I used heat barrier ceramic on the piston domes, chambers and exhaust ports, oil slough coating inside the pistons and on the rods and anti-friction coating on the piston skirts. It's like butter. Hot, sizzling 9500rpm butter!

As I was saying before I sprouted wood......since I'm going to rebuild an otherwise solid engine (it's an affliction) I'll probably have a lot of the parts coated.

Cat: The do appear to be close enough to parallel that it shouldn't be a huge issue though even if there's a bit of misalignment I'll be able to take that up with the rubber carb mounts.

I just bought a Mikuni 45mm Flatslide.....guess I'm committed now.....
 

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Nice, I'm familiar with the internal coatings and have done them for years now.

45 flat or round slide is way too much carb for 30 cubic inches even if it could spin 15,000

I'm thinking even a 40 round slide would be too large and I'm thinking I'd use something in the 34-36mm range

what size are the ports? intake valves?
 

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for reference

a triumph 500 twin running a single carb will do fine with a 26mm and can spin 8K no problem as long as the cams are there and the exhaust doesn't choke it

a hot daytona that has really been breathed on and capable of about 10,000 rpm will do it with 28-32mm carbs

I edited to read 28-32mm instead of 38-32
 

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Discussion Starter #14
Interesting, I'll have to look into this further. At worst I'll let my buddy buy it from me for his Hardly Able To Sportless..
 

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45mm is about right for around 120 inches of Vtwin

even a 40 on a hot 74 incher is a bit soggy
 

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Discussion Starter #16
Eh screw it....I think I'll stick with the VM34s from Sudco....
 

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still curious what size ports that 500 has

I can't imagine any useful port velocity with 34mm ports and I've not ever heard they were prone to eating rings/cylinder walls

what is it's bore and stroke?
 

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Discussion Starter #18
Bore: 70.0mm
Stroke: 64.8mm

Port diameter: approximately 40mm
 

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i have a 4-1 setup for a cb550. and have seen the same for the 750's


jc
 

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wow! 40mm ports? that's really a huge intake port for a 250cc cylinder which is fed by factory 34-35mm CV's. If that's the case I would be willing to bet one could really be woke up by making the port smaller.

I was holding some bare castings yesterday but forgot to look at and inspect the ports. I was more interested in seeing how viable a valve spring conversion is and looks very easy.
 
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