Rejetting vs Fuel flow...wowz.... - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 37 (permalink) Old 10-25-2013, 07:58 PM Thread Starter
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Rejetting vs Fuel flow...wowz....

In the years I been here, I been preachin the "no need to up the jets" thing.....I called it all hype and "one individuals experience"....all the sheep followed though, reduced their MPG.

I had a revelation today....why I was able to run pods and a modified exhaust w/o issues......


.....fuel inlet.... I FORGOT THAT I HAVE HIFLO FUEL INLETS and modded the petcock......makes sense....my fuel is geting shoved into the carbs equally....whereas others may have a petcock issue, one carb starves....etc.......

This is the answer to many VN issues...Ive been running it and never realized....

Replace both carb inlet fittings woth HiFlo brass....increse fuel line size....run a 2 into 1 into 2 line setup from the petcock....both carbs will be fed equally now....even if one petcock side clogs....drill the petcock outlets 1/8" more (larger)...ends up being 1/16" all the way around....flare the inside...its NOT stock....

Follow these small items, and I guarantee you better performance w/o a jet change....

Tired, going to bed....



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post #2 of 37 (permalink) Old 10-25-2013, 09:53 PM
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I got a calculation from WMsonta at one time that is able to make sure you get enough fuel flow to sustain a specific HP, After performing his test, I found my carb did not flow what was needed, I cleaned it out and bam, I got the flow i needed and then some.

I am willing to put money on the fact that folks with fuel issues, just need to clean their carbs. Hi flow into my CVK wont do anything for me, I am sure the limiting factor is the needle valve (on my carb) I don't know about the 750's

you may be on to something


kenny

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post #3 of 37 (permalink) Old 10-25-2013, 11:55 PM
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Merc, you mention that the needle valve is your limiting factor, that is ours as well, that is why we use the #4 washers on the needle valves
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post #4 of 37 (permalink) Old 10-25-2013, 11:58 PM Thread Starter
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See brother....your setup is more like Harley...single manifold to one carb....a lil easier....although I still think a HiFlow would help....

WmSontas test for flow is a static one....all that tells ya is what yer gonna get at idle and low RPMs....as revs go up, fuel demand increases exponentially....

IMO...always better to give the carbs the max flow you can, then let the floats and jets manage it.....but IMO, too many Kawis, yours included, suffer from fuel starvation at higher RPMs....some compensate for it by using larger jets....it may help, but really isnt the answer.....and bottom end may suffer as I proved on Oil City Rd....

Give the carb MORE than the fuel you "think" it needs....then let the carb internals manage it as needed....

Think about it....when your heart pumps faster, it needs more blood coming in, or else it vasculates (I think thats the word)....either way, when the blood aint there, it pumps what...inthe case of a bike, air.....means it goes lean....means it runs hotter....etc etc etc.......

One needs to keep a consistant and sufficient flow to the carbs to have an engine run properly.....the flow needs to be in excess of the actual needed flow.....then there is always fuel waiting in reserve when high volumes are required......

Im starting to sound like a fookin geek....goin to bed....



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post #5 of 37 (permalink) Old 10-26-2013, 08:45 AM
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Question

Funny, since I had been pondering this same question for a while.

I think the foam pods may have a little more restriction than K&Ns, oiled or not. My end caps sit and pulse when the engine is running. Has to be pulling kinda hard to pull the end cap in at least 1/16". The pods look like they're tryin' to signal something in Morse code. You can see every intake stroke happen.

Wolfie, you have Emgo and I have Uni, do yours pulsate?

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post #6 of 37 (permalink) Old 10-26-2013, 10:10 AM
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I have K+n filters and mine pulsate with every stroke.I was wondering if this is normal.

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post #7 of 37 (permalink) Old 10-26-2013, 01:24 PM
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I guess anytime the carb tries to pull more air than it can get, would cause the end cap to move.

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post #8 of 37 (permalink) Old 10-26-2013, 01:58 PM
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Quote:
Originally Posted by MechmanASE53 View Post
I have K+n filters and mine pulsate with every stroke.I was wondering if this is normal.
Yes my k&n's pulsate too

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post #9 of 37 (permalink) Old 10-28-2013, 11:27 AM
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Quote:
Originally Posted by slimvulcanrider View Post
Merc, you mention that the needle valve is your limiting factor, that is ours as well, that is why we use the #4 washers on the needle valves
By needle valve I meant the float needle / fuel valve. No spacers on that.

We are talking fuel flow INTO the bowl.

Or at least I am.

Wmsontas calculation was quite configured for max HP.

With my HP based on the dyno I need to flow 11oz of fuel a minute or something like that.

When I first conducted the test it was 5oz, I cleaned it all out then I got 12oz, that is when my WOT issue went away after clearning up the float needle.

You can put a 8" diameter line into a 1" hole, but it will only flow as fast as the 1" that is my point.

Hi flow is not going to make my needle and float go any faster.

I conducted all my tests with the fuel valve at prime, so vacuum pulses have nothing to do with it, in my case anyway.



I am no carb expert but I know with my single carb I got it tuned pretty well. I have a pilot jet, main jet and needle. Also have the A/F screw too.

I did my tuning using an innovative LM-1 lambda meter and checked it unloaded at multiple RPM. Then I even did some graphs of loaded (real running) while having that beer stein looking thing stick out the exhaust.

Then checked on a real dyno / performance shop and they said it was good, so I am happy.

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 37 (permalink) Old 10-28-2013, 12:23 PM
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Ah my mistake Merc... but you can adjust the float needles too.. just bend the tab a little bit.
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