Horrible miss from 3200-5700 - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
Carbs and Fuel System
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post #1 of 13 (permalink) Old 04-24-2011, 12:37 PM Thread Starter
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Horrible miss from 3200-5700

I have been battling a miss in my bike from ~3200-5700, it is terrible like running on one cylinder and that one is missing type of bad.

I have looked through the posts here and have done the seafoam through a tank and drained the carbs and sprayed with carb cleaner and it slightly improved but it is still horrible.
The plugs all look perfect..
I have come to the realization that I am going to need help with this if I am going to ride this bike.

Would anyone in my area be willing to help take a look @ this with me? I believe the carbs need pulled and cleaned then re-set. I am just not comfortable with trying by myself. I would be willing to put it on the trailer bring it if someone could help. I am in SE Iowa.

Does anyone have any other suggestions to try?

Even though I would like to learn I would be willing to take it to a shop or to someone to get it fixed. If you have any recommendations that would be wonderful.

I talked to one shop yesterday but it would be ~6 weeks before that would even look at it

Bob
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post #2 of 13 (permalink) Old 04-24-2011, 04:18 PM
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Originally Posted by Bobs85GT View Post
I have been battling a miss in my bike from ~3200-5700, it is terrible like running on one cylinder and that one is missing type of bad.

I have looked through the posts here and have done the seafoam through a tank and drained the carbs and sprayed with carb cleaner and it slightly improved but it is still horrible.
The plugs all look perfect..
I have come to the realization that I am going to need help with this if I am going to ride this bike.

Would anyone in my area be willing to help take a look @ this with me? I believe the carbs need pulled and cleaned then re-set. I am just not comfortable with trying by myself. I would be willing to put it on the trailer bring it if someone could help. I am in SE Iowa.

Does anyone have any other suggestions to try?

Even though I would like to learn I would be willing to take it to a shop or to someone to get it fixed. If you have any recommendations that would be wonderful.

I talked to one shop yesterday but it would be ~6 weeks before that would even look at it

Bob
This region seems to breed gremlins in these motorcycles. It could be a lot of things. Can you throttle through this range, or does it just not make enough power to turn past 5700 or so?

Speaking from experience and from what I've read: This band is right about where the needle jet should start to lift. A good place to start might be the big diaphrams. I can remove mine without taking the carbs out, however, with the stock airbox in there I am not sure if you can do that. It is still possible, even with seafoam, that you got a crappy tank of gas that has the jet clogged. Drain the bowls and see if there is a noticeable load of crap that comes out.

Does it idle well?

Just thinking off the cuff here..

1995 VN750 - 10K
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post #3 of 13 (permalink) Old 04-24-2011, 04:24 PM
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Here's just a few things that come to mind...

Have you checked for spark? Might have something to do with the coils or the spark plug cables. Cables could be "leaking" the spark before it actually hits the spark plug or the coils might not be working right. To check for spark you do have to ground the plug though to see if it's working right.

Fuel... Either the carbs really do need to come off and go through a thorough cleaning, or maybe the problem is that they're not getting enough fuel.

You can get some clear fuel line/hose and replace the black fuel lines with the clear ones so you can see if fuel is flowing nicely from the tank to the carbs. Basically, if the lines have fuel in them the whole time, then there's no problem with the carbs not getting enough fuel.
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post #4 of 13 (permalink) Old 04-24-2011, 04:37 PM
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I forgot to ask too, what year is your motorcycle, how many miles, is it California model?

1995 VN750 - 10K
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post #5 of 13 (permalink) Old 04-24-2011, 04:55 PM Thread Starter
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Bike is a 1995, 100% stock, with 10,400 miles.

It idles good, may be a little rough (I assume normal for v-twin), runs great up to 3K, starts the miss but if you hold into it in a lower gear with will power through and smooth out above 5700. In top gear it won't even run 60 @ full throttle just misses, pops, etc. If you are will real smooth on the throttle and keep it @ 3K it will do fine.

Even with no load you can tell the miss in this rpm range.

I will run out and check the spark and report back.

I have drained the bowls and sprayed the gumout up into the carbs, a bunch of crap did come out the first time, the 2nd & 3rd times not so much.

Bob
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post #6 of 13 (permalink) Old 04-24-2011, 05:54 PM Thread Starter
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I went out and pulled the plugs and checked the spark, it was there in all the plugs, though seemed weak, It was thin and more white than the heavy blue I would expect.

Bob
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post #7 of 13 (permalink) Old 04-24-2011, 10:54 PM
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I would say since it will run past that rough spot its *probably* not the ignition system. If its got enough spark to run past the rough spot, it should have enough at any range (although someone else might disagree). I am still suspect of the big diaphragms on the needle jet not lifting when theyre suppose to. Is there ANY way possible to remove these with the airbox in without taking the carbs off?

1995 VN750 - 10K
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post #8 of 13 (permalink) Old 04-25-2011, 01:35 AM
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I've never tried to remove the top caps with the carbs on the bike... I just took out my carbs to inspect and clean them.
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post #9 of 13 (permalink) Old 04-26-2011, 04:19 PM Thread Starter
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Thanks guys. I ended up taking it into the dealer yesterday. We will have to see what they come up with. Looks like I am back to riding the 900F for a couple months .

Bob
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post #10 of 13 (permalink) Old 04-26-2011, 05:00 PM
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Sounds like a clogged main jet , or torn diaphram. Could also be fuel starvation from a bent float, or a clogged fuel line.


Either way does sound like a carb issue to me...let us know what the shop says..

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