Just bogs below 2k, then comes on hard - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 16 (permalink) Old 08-14-2013, 02:28 PM Thread Starter
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Just bogs below 2k, then comes on hard

Maybe this is just how these bikes are, but mine barely responds to throttle below 2k and then it it really wants to GO. It makes it hard to practice maneuvering and I have to ride the clutch just to go up my driveway.

I really don't mind it being a dog at low throttle. Actually I'd like for it to roll on slow but gradually. It just worries me how suddenly it comes on. Something about it doesn't seem right. Do I need to shim my needles or something?
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post #2 of 16 (permalink) Old 08-14-2013, 02:42 PM
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These engines really dont run well at low rpm.. if you think it comes on hard at 2k... try running it up around 6k... the engine has the a stroke of about the width of a gnats' butt... all its power is made at higher rpms
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post #3 of 16 (permalink) Old 08-14-2013, 02:44 PM
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sounds to me like the idle jets are clogged or you are only running on one cylinder at low rpm

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post #4 of 16 (permalink) Old 08-14-2013, 04:03 PM Thread Starter
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Brand new genuine Keihin jets all around, fully cleaned and rebuilt carbs with new diaphragms, and it sounds like it's running on both but I'll check this weekend.
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post #5 of 16 (permalink) Old 08-14-2013, 04:44 PM
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There's something wrong. The comment that these bikes don't run well at low RPMs sounds like another guy with a problem to me....

V-Twins like to run at low RPMs and it does happen that this bike likes to to be wrung out too....your throttle response should be smooth from idle on up. V-twins can put out torque early, and the bike should shouldn't "bog" unless you're in to high a gear for your engine speed.

Keep in mind idle is 1100 rpm, so you're talking about a problem from there to 2000 rpm ?? Could be improper jetting, bad gas, or unrealistic expectations on your part. You shouldn't be running the bike under 2000 RPMs while its in gear unless your accelerating from idle.

If you're saying it isn't responding but then suddenly wakes up... You have a carb/jetting problem.

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post #6 of 16 (permalink) Old 08-14-2013, 05:14 PM
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Quote:
Originally Posted by Knifemaker View Post
There's something wrong. The comment that these bikes don't run well at low RPMs sounds like another guy with a problem to me....

V-Twins like to run at low RPMs and it does happen that this bike likes to to be wrung out too....your throttle response should be smooth from idle on up. V-twins can put out torque early, and the bike should shouldn't "bog" unless you're in to high a gear for your engine speed.

Keep in mind idle is 1100 rpm, so you're talking about a problem from there to 2000 rpm ?? Could be improper jetting, bad gas, or unrealistic expectations on your part. You shouldn't be running the bike under 2000 RPMs while its in gear unless your accelerating from idle.

If you're saying it isn't responding but then suddenly wakes up... You have a carb/jetting problem.
x2!

You should have good throttle response through most of the RPM range with this bike as long you are in the appropriate gear. If you shift too early, below the bikes power band, it won't have the same get up and go as if you shifted higher in the power band and it will feel sluggish. However, if it is bogging down, then the carbs may be getting too much fuel. Might be jets or a stuck float. Have you tried draining the float bowels and back blowing the carbs? Seems like the tinniest dirt particle can cause havoc with these carbs.

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post #7 of 16 (permalink) Old 08-14-2013, 06:53 PM
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Ahh, I dunno, my engine seems happier if I keep it at 2200 rpm and above. Lugging below that is where I got what I thought might be sticking valve, just once in a while. But that hiccup seems to be gone since I put MMO in the oil.

I was also going to say a lean pilot circuit/jet. Mine will pull away from below 2000rpm, but it's lugging.

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post #8 of 16 (permalink) Old 08-14-2013, 11:32 PM
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I'm hoping that wmsonta weighs in on this...he seems to be something of a guru on carbs.

If I had to guess, it would be your air screw settings. I'm also guessing that you have them a little rich.

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post #9 of 16 (permalink) Old 08-15-2013, 12:07 AM Thread Starter
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I set the screws back to 1 1/2 when I rejetted. And like I said, I just completely rebuilt the carbs and used new Keihin brand jets. They're spotless. I've been measuring the carbs from the drain and they're spot on down to the mL. Trust me, it's not a plugged jet or sticking slide or float. I'm leaning toward weak spark or something because everything else seems to check out.

Thanks for the ideas. I'll mess with it more tomorrow and let you guys know what I find out.
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post #10 of 16 (permalink) Old 08-15-2013, 12:28 AM
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I stand corrected, 1 1/2 is waaaay too lean (factory setting is 1 5/8 and that's lean), try adjusting them to 2 then increase in 1/4 turn increments till it better. Mine is set at 2 1/4 on the front and 2 1/2 on the back (that's where she likes it...)



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Last edited by Jakzen; 08-15-2013 at 12:30 AM.
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