Customizing Intake and carbs...flow rates anyone? - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 10 (permalink) Old 06-28-2008, 07:27 PM Thread Starter
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Customizing Intake and carbs...flow rates anyone?

So while my frame is on the back burner at the powdercoaters, I started to clean up my carbs and get ready to do the jet change when I got wondering...how many CFM do the CVK34's flow? How much does the carb on the VN800,900, and 1500 flow? I'm thinking since I have some spare time that I might look into getting some more performance out of the motor. I think it'd be cool to have a custom air box/pipe and a single carb on one side with maybe some more air and fuel through the engine for some extra power.

I know there's a balance between cylinder head flow rates, cam duration & etc., and carburetor flow. I don't want to mess with the heads or cams, just make the most of what's already there. Since it's basically a big air/heat pump, I was thinking about trying to maximize the amount of air and fuel intake while not overloading the motor.

Thoughts anyone? Is this just a pipe dream?
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post #2 of 10 (permalink) Old 06-28-2008, 08:18 PM
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I'm working on something too, probably two 38-40 mm side drafts. I'm also going for a wee bit extra oomph with a slight compression increase, and some mild porting.

I have no idea what the flow rates are, but I'd expect one of the carbs off a 1500 twin should handle a 750 just fine. For dual carbs Id expect something ofg a 800 vulcan or 900 virago with a stub manifold would give a much better flow rate. I'm looking for carbs off of big bore singles, or 800-900 twins. I'd like to find a pair of flat slide carbs if I can geta pair.

85 VN750 basketcase ( yes its a true 750, and no smog controls, its good to be Canadian)
It will have
a rebuilt 96 top end, rebuilt 85 bottom end
degoated, Eared
stripped, lowered, raked, bobbed,
reed valve boxes shaved
ported and polished
balanced
right side dump exhaust
heads and cylinders shaved for compression
looking for smoothbore sidedraft carbs
possibly fat bob tanks
modified vn800 or sportster drag pipes or I'll just make some

Chopperfix
Duck's Garage
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post #3 of 10 (permalink) Old 06-29-2008, 12:34 AM
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I've been wanting a single carb too. No one's mentioned turbo for a power boost.

DT

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post #4 of 10 (permalink) Old 06-29-2008, 10:07 PM Thread Starter
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The carb off a 900 was what I was thinking about. Seeing as how I'm not changing anything like cams, porting & polishing the heads, I don't want to go too big.

DT, I don't think putting any forced induction on our bikes would help a whole lot. At least not without moving to fuel injection. I say that simply because there are no performance heads, valve kits, and cams available for our motors to help better tune the intake, combustion, and exhaust process.

If you're interested though, there's a great project called MegaSquirt and MicroSquirt. You can take a look into them here:
http://www.megasquirt.info/
http://www.microsquirt.info/

Anyway, we'll see what I come up with in the next few days.
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post #5 of 10 (permalink) Old 06-29-2008, 11:31 PM
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I almost bought a turbo, for kicks. Then I sat down and figured out what it would take to make these motors turbo compatible, and I hesitated. Withanything over 1 pound of boost these motors would grenade. You would have to drastically reduce the compression ration and add an intercooler to get a turbo or blower to work Something in the order of 7:1 compression ratio would work. With the torgue of these motors, a turbo would need a lot of tuning to make work, a blower on the other hand, with a properly built engine, could be scary.

85 VN750 basketcase ( yes its a true 750, and no smog controls, its good to be Canadian)
It will have
a rebuilt 96 top end, rebuilt 85 bottom end
degoated, Eared
stripped, lowered, raked, bobbed,
reed valve boxes shaved
ported and polished
balanced
right side dump exhaust
heads and cylinders shaved for compression
looking for smoothbore sidedraft carbs
possibly fat bob tanks
modified vn800 or sportster drag pipes or I'll just make some

Chopperfix
Duck's Garage
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post #6 of 10 (permalink) Old 06-30-2008, 12:42 PM Thread Starter
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Any kind of forced induction is beyond my scope of experience and really kind of scares me to think about anything like that on a bike. lol Though I wish there were more aftermarket parts for these engines. Performance cams or heads would be sweet. But we gotta work with what we got. Oh well.

Duck, what are the differences between CV carbs and flat slide carbs?
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post #7 of 10 (permalink) Old 06-30-2008, 03:39 PM
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IIRC In a CV carb the needle position is determined by engine vacuum. Flat slides and standard round slide carbs have no diaphram, needle position is determined by the height of the slide and is much easier to tune. Flatside generally flow better than the older round slides. and are more consistent in fuel delivery.

85 VN750 basketcase ( yes its a true 750, and no smog controls, its good to be Canadian)
It will have
a rebuilt 96 top end, rebuilt 85 bottom end
degoated, Eared
stripped, lowered, raked, bobbed,
reed valve boxes shaved
ported and polished
balanced
right side dump exhaust
heads and cylinders shaved for compression
looking for smoothbore sidedraft carbs
possibly fat bob tanks
modified vn800 or sportster drag pipes or I'll just make some

Chopperfix
Duck's Garage
Duck is offline  
post #8 of 10 (permalink) Old 07-01-2008, 11:42 AM Thread Starter
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That explains the constant velocity part of the name. It also explains the large airbox under the tank. Thanks Duck! That explains a few other things too.
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post #9 of 10 (permalink) Old 07-01-2008, 12:30 PM
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If you can find them, Mikuni Smoothbores are supposed to be really easy to tune.

85 VN750 basketcase ( yes its a true 750, and no smog controls, its good to be Canadian)
It will have
a rebuilt 96 top end, rebuilt 85 bottom end
degoated, Eared
stripped, lowered, raked, bobbed,
reed valve boxes shaved
ported and polished
balanced
right side dump exhaust
heads and cylinders shaved for compression
looking for smoothbore sidedraft carbs
possibly fat bob tanks
modified vn800 or sportster drag pipes or I'll just make some

Chopperfix
Duck's Garage
Duck is offline  
post #10 of 10 (permalink) Old 07-01-2008, 12:54 PM Thread Starter
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I'll keep that in mind when I'm looking around. For the moment, I'm gonna continue working with the stockers and just re-jet and ear shave. But I'll keep my eyes and ears open for anything else that might work better. If I do find something, that may be my winter project.
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