Gravity feed petcock question(s) - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 15 (permalink) Old 07-02-2008, 09:10 PM Thread Starter
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Gravity feed petcock question(s)

Pulled off the o-ring and spring from the piston in McKnight's petcock to help out a fellow rider. So now I'm on a gravity feed until I get the replacement bits. I blocked off the vacuum line from the petcock and the line from the nipple on the front carb (one hose on each, blocked off with sundry parts). But the bike's running lean like...like...well, lean like a European Super Model (as in "so lean it's not healthy"). Do I need to block off the rear vacuum port as well? If so, why? And if not, why not? I understand the vacuum operation on the front carb, but I'm clearly not getting it on the rear one.

Oh, and does anyone happen to know - just offhand - the spring number for the piston? Ayers has the o-ring as a 4mm, but no info on the spring.

Thanks.

C

Last edited by Crobins365; 07-02-2008 at 09:11 PM. Reason: Forgot to ask about the spring
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post #2 of 15 (permalink) Old 07-02-2008, 09:28 PM
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The rear vacuum port is usually tied to the reed valve system and supplies vacuum for the valve that operates them. If you've coastered, you should have blocked off the rear vacuum port, otherwise you'll run lean as air is being sucked into the air/fuel mix that wasn't meant to be there.

You may have to just use a similar size/shape spring as I can't find any measurement data on it either without tearing mine apart.

Jim W
93 VN 750 "Ursula"
Moved R/R 08Sep06
R/R rewire 17Feb07
New R/R, Installed 14Jun08
New Stator installed 10 Jun08
Maintenance Free Battery 12Jan08
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post #3 of 15 (permalink) Old 07-02-2008, 09:30 PM Thread Starter
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Thanks. I haven't coastered, just broke down the petcock. Maybe I *should* coaster, block off the rear vacuum line, and see if it runs any better? That might take care of some of the leanness!

C
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post #4 of 15 (permalink) Old 07-02-2008, 10:02 PM
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If the rear vaccum port isn't connected to anything, that would cause the lean condition, at least on the rear cylinder. If the vacuum line is still connected to the valve system, you shouldn't be running lean.
From your post it sounded like the rear port was open. The reeds actually cause the bike to run rich IIRC. The line may have become disconnected from the valve which sits in front of the battery box.
Is Orleans' ghost starting to haunt Mcknight??

Jim W
93 VN 750 "Ursula"
Moved R/R 08Sep06
R/R rewire 17Feb07
New R/R, Installed 14Jun08
New Stator installed 10 Jun08
Maintenance Free Battery 12Jan08
21480 Miles
VROC #8542
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post #5 of 15 (permalink) Old 07-02-2008, 10:18 PM Thread Starter
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Originally Posted by Sky Rider View Post
Is Orleans' ghost starting to haunt Mcknight??
Aaaaaaaaaaaaaaaaaaaa! Perish the thought!!! I think I just futzed around with too many things at once. I'll check all my connections again this weekend - it's probably something simple. If not, anyone wanna buy an '01?

C
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post #6 of 15 (permalink) Old 07-02-2008, 10:58 PM
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Does marbling produce the same effects?

Rckmtn
Dennis Huff
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Last edited by rckmtn; 07-02-2008 at 10:58 PM. Reason: spelling
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post #7 of 15 (permalink) Old 07-03-2008, 07:49 AM Thread Starter
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Does marbling produce the same effects?
Haven't tried it yet, but I will this weekend. I've been wondering if I don't need to marble - PO did, I undid, and the bike without has been popping and sputtering as long as I've had it. Definitely need to check connections and put the spring and o-ring back in the petcock, but I've been thinking there may be other things going on that are leaning out the ride.

I sounded like a really sick HD last night!

C

Last edited by Crobins365; 07-03-2008 at 07:57 AM.
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post #8 of 15 (permalink) Old 07-03-2008, 08:33 AM
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I have a rebuilt Petcock...that i would consider trading...???
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post #9 of 15 (permalink) Old 07-03-2008, 12:25 PM Thread Starter
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Originally Posted by slimvulcanrider View Post
I have a rebuilt Petcock...that i would consider trading...???
What're you up for? I've got parts and parts - although, if I read Ayers correctly, the o-ring and spring will cost me about $2.00 (plus $9 shipping ). Seriously, though, what d'ya need? We might be able to swing a deal!

C
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post #10 of 15 (permalink) Old 07-03-2008, 03:12 PM
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not so much as a need, but i would like to have a stator side cover to work with...i am trying to come up with a DIY mod for removing the Stator inside the bike...Just need a cover to start monkeying around with...but I don't think you need my petcock that much.
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