Looses power in high rpms - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 9 (permalink) Old 02-04-2016, 12:18 PM Thread Starter
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Looses power in high rpms

I have '98 750 I shaved the ears and straight piped it. My rear carb diaphragm is not pulling the metering rod up yet the cylinder seems to run fine with the exception that the bike doesn't seem to have as much pep and in high gear it falls off around 6000 rpm and you do good to get past 6500. The bike starts and idles
fine. There is some back fireing threw exhaust and occasionally carbs at low rpm please help
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post #2 of 9 (permalink) Old 02-04-2016, 12:59 PM
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the carb experts will jump in here, but to me it sounds like a broken/leaky diaphram for the slide.. when you push the slide up and release, do you hear a nice even 'whoosh'?

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post #3 of 9 (permalink) Old 02-04-2016, 04:17 PM
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Originally Posted by michiganteddybear View Post
the carb experts will jump in here, but to me it sounds like a broken/leaky diaphram for the slide.. when you push the slide up and release, do you hear a nice even 'whoosh'?
That would be my first guess, then a dirty main jet or low float level.

Your carb vent is located where? Sheltered from wind?

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post #4 of 9 (permalink) Old 02-04-2016, 08:32 PM Thread Starter
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I'm sorry it takes me so long to reply I'm very busy with kids. I do really appreciate yals input. In regards to your questions #1 your defiantly on to something and I'm like duh. No whoosh. Why didn't I think of that I appreciate you waking me on that one lol.
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post #5 of 9 (permalink) Old 02-04-2016, 08:35 PM Thread Starter
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#2 wind can probably get to my vent my problem of it opening does it at idle sitting still. I doubt the wind would play a role in that situation but should this still be a concern , vent exposed to wind that is?
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post #6 of 9 (permalink) Old 02-04-2016, 10:28 PM
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Wind hitting the vent can create pressure in the fuel bowl and prevent gas from entering. Best spot for the end of the hose is tied to the frame under the tank, or on the blank nipple where the fuel gauge sender is bolted to the bottom of the tank.

Does sound like the diaphragm is cracked or out of position, not sealing.

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post #7 of 9 (permalink) Old 02-04-2016, 10:48 PM
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Hehehe he said blank nipple.

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post #8 of 9 (permalink) Old 02-05-2016, 02:42 AM Thread Starter
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Thank you my diaphragm was not seated well around the outer edge that being corrected I zipp tied my vent to the frame and my diaphragm problem see cured. My powers back and now on to sync the carbs Ty again
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post #9 of 9 (permalink) Old 02-05-2016, 10:40 PM Thread Starter
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http://www.powerchutes.com/manometer.asp. I'd like to add that anyone having carb sync problems needs to check out the above link . I tried it and for three dollars and very little time or effort it worked beautifully. This guy hit it right on. Thanks to all who've helped me out. Hopefully I'll be able to pay it forward
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