Help calculating jet size? - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 6 (permalink) Old 07-20-2013, 11:02 AM Thread Starter
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Help calculating jet size?

I've seen people offering to calculate jet sizes, but I have no idea how to do it myself. It woudl be nice to do this while I have the carbs out for cleaning/rebuilding anyway.

Nearest towns range from 670 to 890 ft elevation. This state varies from 480-1670, average 1100.

I'm going to shave the ears and coaster on a stock exhaust for now. I'm not planning to de-goat to an H-pipe because I hear the pre-muffler deepens the tone.

Thanks in advance for any help you can give me.

Jason
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post #2 of 6 (permalink) Old 07-20-2013, 11:14 AM
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I have calculated the jet sizes and given them in relation to stock (OEM).

https://www.vn750.com/forum/showthread.php?t=32778
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post #3 of 6 (permalink) Old 07-20-2013, 11:42 AM
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I set up my bike to run from 0-2000 feet elevation, running 142-40 jets, and 2 shims under the needles. Ear shave stock exhaust.
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post #4 of 6 (permalink) Old 07-20-2013, 12:29 PM
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Arrow No Re-Jet For Me

I'm at 600ft, earshaved, coastered, w/stock pipes, and I didn't need to rejet. Have never had the carbs open or even off the engine, so I don't know what's in there for certain. But unless someone went to the trouble to put this bike back to stock configuration and left bigger jets in there(not likely), I have to assume they are stock size.

I wouldn't expect elevation to come into play until I got to around 4500ft, I routinely reach 2000-2500ft on my rides and have no trouble. I know the barometric sensor on my car didn't activate until I got to 4500ft.

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post #5 of 6 (permalink) Old 07-22-2013, 10:44 PM Thread Starter
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So anywhere from stock to 4 sizes up? That's a pretty big range for the same engine with the same mods. I'd rather not have to order 4x as many parts and swap things over and over again if I can get it close the first time.
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post #6 of 6 (permalink) Old 07-22-2013, 10:54 PM
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I do not tell grown ups what to do, I do tell them what I would do.

I would leave it OEM or #38, #135, no shims. That said, I do not see OEM intake as a restriction.

Forum consensus is as slim posted above.
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