Jet Question - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 9 (permalink) Old 11-02-2007, 08:20 PM Thread Starter
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Jet Question

97 Vulcan 750, Shaved, De-Goated, Coastered, Jetted to 142 rear, 140 front, 40 Pilot. How can I tell if at wide open throttle, if it is running rich or lean? Any advice, or suggestions?

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post #2 of 9 (permalink) Old 11-03-2007, 09:43 AM
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Well, I've never done this on a streetbike, but on dirtbikes we'd get it up to speed, then pull in the clutch, shut the engine off and coast to a stop, then check the plugs to see how they looked.

If doing this on a streetbike, it'd be best to have an open, little used road with a safe place to pull over once you come to a stop

And watch out, everything will be HOT!


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post #3 of 9 (permalink) Old 11-03-2007, 10:20 AM
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Does anyone know of a different way to determine correct jetting? The method Hyper outlined is what I've used over the years but is there another way?
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post #4 of 9 (permalink) Old 11-03-2007, 11:15 AM
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They make a device that allows you to see inside the combustion chamber.I'll check out some of my old links and see if I can find it. It was on one of the older personal 750 web sites.

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Last edited by rckmtn; 11-03-2007 at 11:16 AM. Reason: spelling
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post #5 of 9 (permalink) Old 11-06-2007, 01:05 PM
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color tune

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post #6 of 9 (permalink) Old 11-07-2007, 05:28 PM Thread Starter
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Colortune / Jets

My concern with colortune is that the bike wouldnt have a load on it and I wouldnt be able to rev it that high safely to see if it was firing correctly. I was hoping that there might be some older drag racers familiar with "seat of the pants tuning" that could offer some advice here. Shouldnt there be an indication of running to rich or to lean by performance / power?

Kuryakyn Flame Grips
Bar End helmet locks
Chrome / Gold "Live to Ride Mirrors"
Coastered, Shaved & Jetted
K&N Pod Air Filters
KisanTech headlamp & Taillight modulators
Iridium's
Leather Lyke Hard Bags
Voltmeter, Clock
Stebel Nautilus horn
Slipstreamer SS28
J&M CB Radio
Audiovox CCS-100 Electronic Cruise Control
Mustang Seat, Protac Drivers Backrest
And of course the obligatory stator replacement[/FONT]
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post #7 of 9 (permalink) Old 01-06-2008, 10:16 PM
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Best way to test the bike with the new gas and additives is NOT by reading the plugs. In face if the bike is close to correct you should not see any but the slightest change in plug color at all.

But there is a way to determine just how the TOP end jetting is on allmost any bike. Get up to speed in third gear at about 3/4 throttle. If you whac the throttle open and the bike boggs down or stumbles momentarily, it's ususlly lean. If the bike wants to accellerate but seem like its sluggish, back off the throttle slightly. If it then takes off, it's usually Rich.

While this works better than seat of the pants tunning, it won't be anywhere as good as a good dyno and carb setup by a professional.

Nick
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post #8 of 9 (permalink) Old 01-07-2008, 12:04 AM
punch a hole in the wind!
 
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I assume that youre gonna tune you bike knowing this: the best place to test it is a flat desert road having good engine temperature on a mildly fresh day(for low humidity) and if possible on a low altitude place. Consider also using good fuel and new plugs if you must.
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post #9 of 9 (permalink) Old 01-07-2008, 12:15 AM
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I know that a bike tunned too lean tends to accelerate hard on the upper revs, but slugs on the higher gears al low rpms. When its too rich, the bike pulls hard at low rpms, but it tends to loose some power at high end. Our bikes tend to run lean from factory ,if you use performance jets the first notable impression will be at low rpms pulling a lot better than stock. It is usual that people set the carbs based on low rpm driving, but if you want the bike to kick ass concentrate on leaner settings and high end power, as there is the real goal on horsepower advantage.
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