Carb flow rate - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 32 (permalink) Old 07-18-2013, 11:27 PM Thread Starter
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Carb flow rate

All... I have a VN800 drifter wih the single Kehin 36mm carb or is it a CVK 34- I forget.. but anyway, I was wondering how fast fuel should flow out of the drain on the bowl?

I have this interesting issue when driving, if I go wide open the bike leans out badly, starves for fuel, but if I let it fill the bowl again it seems fine.

I checked tank vent, that seems ok.

I noticed when I open the bowl drain it pours out fast, then slows down to just over a trickle....

I had the petcock on prime and fuel cap open and fuel cap closed (no difference there)

I was wondering how much fuel can a bike burn at WOT and what kind of flow rate should I be looking for?

I am starting to think i have something stuck in my fill needle valve OR the floats are set to low.

iddeas?

I may pull the carb friday / sat and clean it out really well, maybe even drain some of the tank.

kenny
kenny

Merc
2000 Vulcan Drifter 800
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post #2 of 32 (permalink) Old 07-19-2013, 12:02 AM
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Did you change anything?

Give me the hp and I can easily figure how many oz's per min or 30 sec. I have had some trouble with petcocks not flowing enough. The last one would appear to wind out in low, only about 6k in2nd, 5500 in 3rd, etc.
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post #3 of 32 (permalink) Old 07-19-2013, 12:32 AM
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Try doing the same thing with the throttle open. You may be drawing an internal vacuum inside the carb when draining the bowl.

I changed my petcock to a non vacuum operated one (TW200) because manifold vacuum decreases as the throttle opens. I didn't want to have to deal with an artificial lean condition because of possible reduced vacuum not properly operating the petcock.

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post #4 of 32 (permalink) Old 07-19-2013, 11:11 AM Thread Starter
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Quote:
Originally Posted by wmsonta View Post
Did you change anything?

Give me the hp and I can easily figure how many oz's per min or 30 sec. I have had some trouble with petcocks not flowing enough. The last one would appear to wind out in low, only about 6k in2nd, 5500 in 3rd, etc.

I think it was about 59HP, 51 ft lbs torque max.


Quote:
Originally Posted by Jakzen View Post
Try doing the same thing with the throttle open. You may be drawing an internal vacuum inside the carb when draining the bowl.

I changed my petcock to a non vacuum operated one (TW200) because manifold vacuum decreases as the throttle opens. I didn't want to have to deal with an artificial lean condition because of possible reduced vacuum not properly operating the petcock.

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No change even with petcock on prime, with petcock on or reserve it does not flow, which is ok.

Merc
2000 Vulcan Drifter 800
Roadhouse classic 2 > 1 exhaust
Okie Smokie intake config
Changed jets
52K miles or so, always going up
Corbin Seat
Painted flat black winter '12
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post #5 of 32 (permalink) Old 07-19-2013, 12:15 PM
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Quote:
Originally Posted by Mercury View Post

I think it was about 59HP, 51 ft lbs torque max.



11.6 oz's per minute. At least 10% margin. Rounds off to 13 oz per minute, 6.5 oz in 30 sec minimum. This is delivery to the carbs, so flow though the hoses, etc.
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post #6 of 32 (permalink) Old 07-19-2013, 12:25 PM Thread Starter
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Quote:
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11.6 oz's per minute. At least 10% margin. Rounds off to 13 oz per minute, 6.5 oz in 30 sec minimum. This is delivery to the carbs, so flow though the hoses, etc.
thank you, I will have to check if I get that much fuel flow, I have something I can allow it to flow into.

If the flow rate is good, me thinks my main jet needs a cleaning

thank you

ken

Merc
2000 Vulcan Drifter 800
Roadhouse classic 2 > 1 exhaust
Okie Smokie intake config
Changed jets
52K miles or so, always going up
Corbin Seat
Painted flat black winter '12
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post #7 of 32 (permalink) Old 07-19-2013, 05:24 PM Thread Starter
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the way i checked this was to use the drain on the bowl, timed it for 1 minute, ended up with < 5oz of fuel.

Note I have one carb.

I am going to pull that carb and go clean everything up inside there, see if that changes the flow.


gas cap on or off made no diff

thanks for the experiment.

kenny

Merc
2000 Vulcan Drifter 800
Roadhouse classic 2 > 1 exhaust
Okie Smokie intake config
Changed jets
52K miles or so, always going up
Corbin Seat
Painted flat black winter '12
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post #8 of 32 (permalink) Old 07-19-2013, 06:09 PM
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That probably won't work, Merc. I would test the petcock.

No engineering incentive to have a faster drain.

5 oz a min would only support about 25 hp.

Last edited by wmsonta; 07-19-2013 at 06:11 PM.
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post #9 of 32 (permalink) Old 07-19-2013, 08:21 PM Thread Starter
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Quote:
Originally Posted by wmsonta View Post
That probably won't work, Merc. I would test the petcock.

No engineering incentive to have a faster drain.

5 oz a min would only support about 25 hp.
Hey there, so I cleaned out the carb, i noticed the fuel needle has a screen in the port where the needle sits. Could not get screen out so just sprayed gumout backwards through the line, put it all together and checked flow - 12oz one minute....


NOW for the highway test!

Be back soon with results

kenny

Merc
2000 Vulcan Drifter 800
Roadhouse classic 2 > 1 exhaust
Okie Smokie intake config
Changed jets
52K miles or so, always going up
Corbin Seat
Painted flat black winter '12
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post #10 of 32 (permalink) Old 07-19-2013, 10:13 PM Thread Starter
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WHOLLY CRAP!

The bike pulls like it never did before, thanks for the flow info WM - hey, how do you calculate that anyway?

Hit the highway, wound out 3ed gear pretty high, not to red line, normally when I shift into 4th it falls on its face, IT KEPT PULLING, I dropped out of WOT when I got to 105, too much traffic.

But WOW, I guess that screen was a little dirty!

Thank you all!

This worked, bike is perfect now, well I noticed the rear brake does not activate the brake light, easy fix, I know electronics, in the day time!

kenny

Merc
2000 Vulcan Drifter 800
Roadhouse classic 2 > 1 exhaust
Okie Smokie intake config
Changed jets
52K miles or so, always going up
Corbin Seat
Painted flat black winter '12
Mercury is offline  
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