bike lean effects idle? all sorts of carb ques... - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 16 (permalink) Old 09-24-2011, 04:05 PM Thread Starter
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bike lean effects idle? all sorts of carb ques...

I have a 05 750 vulcan. I just took my carbs off for a cleaning. the bike would only run with the choke on.
put it all back together and now it idles great. but i can't get pass 4500 rpm. it just breaks up and bogs out. set the air screws 2 turns out. I did not sync them. could that be it? I did not have this problem before cleaning.
When I had both of the carb bodies off of the float bowl assembly for cleaning, I somehow managed to flip flop the carb bodies on assembly. I noticed when the choke cable assemby came in from the wrong side of the bike. I just flipped the choke assembly around to face the right way. Is that OK? There is no primary carb is there? Aren't they identical?
I noticed that when I put it on the side stand the bike idles up to 2000, pick the bike upright and it idles nicley at 1400, lean the bike to the right and it starts falling off and eventually stalls. Pulled the plugs, front clnder looks good, rear are black as night. like carbon fouled not fuel.
Also I did the coastering mod at the same time. I blocked off the reed valves and plugged the vac line on the right side carb. I left the rest of the valve body under the seat with the rest of the lines still hooked into it.
What is the valve under the oil tank? it has vac lines going to the gas tank and to the surge valve under the seat.
Where can I get a service manual online?
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post #2 of 16 (permalink) Old 09-24-2011, 06:33 PM
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Lots of peoples have chimed in with some of the problems your talking about. There are lots of photos and stuff here about the jets. From what i have read the idle adjustments only work at idle and from what ive read the main jets kick in after ,, around or about 3000 to 4000 rmp sounds like one of the jets still may be clogged or have trash in it. Could also be float settings, so look around,, lots of good ppls here and im sure someone else will chime in soon with more info.
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post #3 of 16 (permalink) Old 09-24-2011, 06:37 PM
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Welcome to the Vulcan madness Adam.

Have you been riding the bike for a while before removing the carbs, or is it a recent purchase?
I don`t have any hands on experience with the vn carb, so I can`t say how "flip flopping" the carb bodies on the float bowls will affect it. But you are right, they are basicly identical, one carb for each cylinder.

Synchronizing the carbs is desirable after taking the carbs apart for cleaning.
However with a twin cylinder engine you can come very close just by adjusting the throttles to start opening at the same time.

Hopefully Crobins or one of the others with more carb experience will weigh in here soon and be able to tell you if you need to pull the carbs apart again and reassemble them with the parts back in their original positions.

US bikes have some emission control valves, hoses and canisters behind the engine and under the seat that my Canadian bike doesn`t have. The VN does not have an oil tank, is has a wet sump with all the oil in the crankcase. What you call an oil tank is probably one of the canisters.

Here is a link to Kanuck69`s thread where he introduces a new and improved VN750 service manual:
https://www.vn750.com/forum/showthread.php?t=17667

Hope this helps.

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post #4 of 16 (permalink) Old 09-26-2011, 04:43 PM Thread Starter
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thanks for the info guys.
When I say it will not rev past 4500, I mean when it is being driven(load on the engine) It will idle smoothly and rev to the moon all day long in the garage. What gives?
Still would like to know what that valve is that connects to the bottom lines on the gas tank and If I missed somthing in the coastering mod that would make it run this way.
Thanks again.
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post #5 of 16 (permalink) Old 09-26-2011, 06:25 PM
If only it had 6th gear..
 
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I managed to copy over this reply thus annihilating it... sorry.

Dave

Mods:
Jetted, shaved & coastered
Home made under-tank single filter
Converted ACCT's to manual (thanks wib714)
Dual vac lines on petcock (my cure for ticking)
LED tail/plate lights
Relocated helmet lock to license plate

Added stuff:
Customized hard bags w/ lights
Chrome levers
Hellcat windscreen
LED running lights
Home made 'Vita-Volt' meter
Foot rests on engine guard
Tunes

Hmm....she was on the back when we left.... ??

Last edited by DavesVulster; 09-27-2011 at 11:02 PM.
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post #6 of 16 (permalink) Old 09-26-2011, 09:30 PM
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If you got the needles mixed up you will have problem.
I am not sure what problem it causes but it does mess some thing up.

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post #7 of 16 (permalink) Old 09-27-2011, 08:56 AM
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Being a V twin, it's common for the front cylinder carb to have a different size carb jet than the rear cylinder. I think the rear cylinder has the bigger jet because it tends to run hotter due to less air flow around the cylinder. I think you would want to have that carb installed exactly as it was originally.

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post #8 of 16 (permalink) Old 09-27-2011, 05:36 PM Thread Starter
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thanks for the response guys. the needles have been swapped. that would make sense because that is part of the RPM range I am having trouble with. as I said before the front spark plugs looked great but the rear plugs were dark black with carbon. The needle swap still would not explain the change in RPM at idle when leaning the bike back and forth. What is the float set height?
When driving the bike takes of from idle to 4000 rpm very nicely but the breaks up an will not rev any higher, additional throttle causes the bike to bog then very light and short surge.
Again when running on the side stand it pulls thru the RPM range and comes right back down to idle.
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post #9 of 16 (permalink) Old 09-27-2011, 10:39 PM
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I've not done any carb work on mine, nor shaved the ears (yet) but I have a similar issue. Bike runs great till I am around 5000rpm. Then it seems to start chugging a bit and losing power. Been that way ever since I got it.

Hoping that when I eventually do the ear shave and new jets this will help clear that up.

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post #10 of 16 (permalink) Old 09-27-2011, 10:49 PM
If only it had 6th gear..
 
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Well I'd say that you're bike is starving for fuel in the upper rpms ... but you said your rear plugs are black so that could be your plugs aren't maintaining spark at higher rpm BUT....

It wasn't doing this b4 the carbs were removed/replaced and jets were not changed correct?

Did you skip anything at all when putting it back together (are you running it without the air cleaner covers on?) If you just have the filters in place but not the cases you'll lose your top end because of too much air.

Another thought How long have those plugs been black? Only since reinstalling the carbs or b4? What about swapping them with the front (or replace them) to get a fresh prospective of what's doing in there? Engines don't flood at higher rpms, unless ignition breakdown occurs. Even when both of my float valves were stuck open I could redline my bike until she came back down to earth at 2500 or so and then she'd flood out... to the point of dripping out of the carbs. Pretty severe. So, going back to the statement that it didn't do this b4, we can probably assume spark is not an issue.

Dave

Mods:
Jetted, shaved & coastered
Home made under-tank single filter
Converted ACCT's to manual (thanks wib714)
Dual vac lines on petcock (my cure for ticking)
LED tail/plate lights
Relocated helmet lock to license plate

Added stuff:
Customized hard bags w/ lights
Chrome levers
Hellcat windscreen
LED running lights
Home made 'Vita-Volt' meter
Foot rests on engine guard
Tunes

Hmm....she was on the back when we left.... ??

Last edited by DavesVulster; 09-27-2011 at 11:13 PM.
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